Freshwater Catfish Recovery Plan

A Resource Document Volume

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Pam Clunie & John Koehn

Freshwater Catfish: A Resource Document Pam Clunie and John Koehn

Freshwater Ecology Arthur Rylah Institute for Environmental Research Department of Natural Resources and Environment 123 Brown Street, Heidelberg VIC 3084 tel: (03) 9450 8600 fax: (03) 9450 8730

July 2001

ISBN 978-1-74208-122-9 (Print) ISBN 978-1-74208-123-6 (Online)

Final Report for Natural Resource Management Strategy Project R7002 to the Murray Darling Basin Commission

Freshwater Catfish – A Resource Document

The preparation of this publication was funded by the Murray Darling Basin Commission, Natural Resource Management Strategy and Department of Natural Resources and Environment, Victoria. The views expressed are those of the authors and do not necessarily reflect those of the Murray Darling Basin Commission. Copyright © 2001 Apart from fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act, no part of this publication may be reproduced by any means without the permission of Murray Darling Basin Commission.

Acknowledgments The authors which to thank all staff of the Freshwater Ecology Group, in particular John McKenzie, John Mahoney, Damien O'Mahony, Louise Grgat, Tom Ryan, Steve Saddlier, Ivor Stuart, Jason Lieschke and Justin O'Connor. The authors also wish to thank Bill O'Connor and Julia Reed, Parks Flora and Fauna, Alan Baxter, Craig Balinger, Fisheries, Department of Natural Resources and Environment, Brett Ingram, Geoff Gooley and Gus Strongman, Department of Natural Resources Snobs Creek, Pam and Jeff Norman 'Narrawong', Ray Mephan 'Little Valley', Alistair Dove University of Queensland, Jane Roberts CSIRO, Alex Hamlyn Department of Primary Industries, Andrew Sanger, Alan Lugg, Cameron Lay, Paul O'Connor, Craig Schiller, Ian Lyall NSW Fisheries, Warren Martin, Deborah Love Department of Land and Water Conservation, Robyn Watts Charles Sturt University, Anthony Moore, Southern Cross University, Phil Cadwallader Queensland Fisheries Management Authority, Lance Lloyd Murray Darling Basin Commission, , John Humphrey, Department of Natural Resources and Environment, Mark Lintermans, Environment ACT, John Winwood, formerly SA Recreational Fishing Council, Ross Hyne, New South Wales Environment Protection Agency and John Whittington, New South Wales Agriculture. Recovery Team Membership: • John Koehn, Manager, Freshwater Ecology, Arthur Rylah Institute for Environmental Research, Parks, Flora and Fauna, Department of Natural Resources and Environment • Pam Clunie, Freshwater Ecology, Parks, Flora and Fauna, Department of Natural Resources and Environment • Tarmo Raadik, Freshwater Ecology, Parks, Flora and Fauna, Department of Natural Resources and Environment • Dr Stuart Rowland, NSW Fisheries, Grafton, New South Wales • Dr John Harris, formerly NSW Fisheries, New South Wales • David Moffatt, Department of Natural Resources, Toowoomba, Queensland • Dr Michael Hutchison, Department of Primary Industries, Deception Bay, Queensland • Dr Clive Keenan, Department of Primary Industries, Bribie Island, Queensland • Dr Alistair Brown, Aquatic Ecosse, Melbourne, Victoria • Linda Selg, Environment Australia Freshwater Ecology, NRE & Murray Darling Basin Commission

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•

Bryan Pierce, South Australian Research and Development Institute

Steering Committee Membership: • John Koehn, Manager, Freshwater Ecology, Parks, Flora and Fauna, Department of Natural Resources and Environment • Pam Clunie, Freshwater Ecology, Parks, Flora and Fauna, Department of Natural Resources and Environment • Brian Lawrence, Murray Darling Basin Commission, Canberra • Dr Alistair Brown, Aquatic Ecosse, Melbourne, Victoria. • Dr Martin Mallen-Cooper, Fishways Consulting Services, Sydney, New South Wales

Freshwater Ecology, NRE & Murray Darling Basin Commission

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Summary This document outlines the existing biological information for freshwater catfish Tandanus tandanus and reviews existing and potential threats to the species, including an assessment of their possible roles in the species' decline. It was prepared as the first step in developing a recovery plan for freshwater catfish (Clunie and Koehn, in press). It is essential to understand the available knowledge and knowledge gaps when determining recovery actions for a species. This ensures that decisions can be made using the best possible information and that research efforts are not repeated unnecessarily. The collation of information for this project has indicated that freshwater catfish has significantly declined within the majority of the Murray Darling Basin and its conservation status has been reassessed by the recovery team to vulnerable in accordance with the IUCN classification system. Declines have been observed in some areas since the 1950s, while in many others since the late 1970s and 1980s. While freshwater catfish are still recorded in low numbers throughout many areas of the Murray Darling Basin, it is evident that there are now few areas where the species could be considered abundant. Queensland currently represents the stronghold of the species and its protection in this area must be seen as the highest priority. Other large populations within the Murray Darling Basin primarily occur in large impoundments within New South Wales, as well as only a few riverine sites such as the Wimmera River in Victoria where the species has been introduced. Freshwater catfish occurs in a wide range of habitats, although it appears to show a preference for slower flowing areas. Fish are often found in the vicinity of some form of structure such as aquatic vegetation, undercut banks and root masses, although the importanc eof particular habitat components is not well understood. Adtuls do not seem to be generally migratory, athough movement patterns of all life stages requires further investigation. The species breeds between October and March across its range and spawning appears to be primarily stimulated by rises in water temperature. Fish lay demersal eggs in nests, commonly made of pebbles and stones, which they guard. Freshwater catfish, which are usually solitary, are predominantly opportunistic carnivores. Freshwater catfish naturally occurs throughout the entire Murray Darling Basin, an area which encompasses a wide range of climates, habitats and environmental conditions. There are numerous threats which exist across its range and various combinations of threats operate in different ways, over different areas and different timeframes. This resource document reviews threats in the following categories; river regulation, introduced species, water quality, instream and surrounding habitats, diseases, fishing and breeding and genetic issues. Many threats are closely interlinked and complex, making it difficult to distinguish between causes of decline and the effects of threats. Our knowledge of the distribution and severity of particular threats, as well as their impact on the aquatic environment and individual species is incomplete. The reviews of each threat Freshwater Ecology, NRE & Murray Darling Basin Commission

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outline background, management and an assessment of the significance of each threat. Some research has been undertaken on freshwater catfish, however there is much we do not know if its ecological requirements or its response to many threats. There is no doubt the species has suffered a significant decline throughout the majority of its range, this decline occurring over many decades but there is a lack of detailed information to provide an accurate pattern of decline for particular areas. How each threat specifically affects freshwater catfish is also an important factor. For example, whether a threat causes sublethal or lethal affects and whether it affects each life history stage is crucial to understand. There is also often a time lag between the occurrence of a particular threat and when the ecological consequences are recognised. In this context, we cannot definitively state exact reasons for the decline of freshwater catfish. It is likely that numerous threats have contributed to this decline, although some are clearly more significant and broad ranging than others. Threats such as river regulation have affected the majority of rivers within the Murray Darling Basin in a range of different ways, while other such as predation by redfin Perca fluviatilis or particular pesticides only affect specific areas. While the significance of some threats can be reasonably predicted others, others such as diseases are entirely unknown and cannot be assessed without specific research.


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Freshwater Catfish – A Resource Document CONTENTS

ACKNOWLEDGMENTS............................................................................................................................. I SUMMARY.................................................................................................................................................III SECTION 1 - EXISTING ECOLOGICAL INFORMATION ................................................................. 1 1 INTRODUCTION .................................................................................................................................... 1 2 DESCRIPTION ........................................................................................................................................ 2 2.1 TAXONOMY .......................................................................................................................................... 2 2.2 GENETICS ............................................................................................................................................. 4 3 DISTRIBUTION ...................................................................................................................................... 7 3.1 PAST DISTRIBUTION.............................................................................................................................. 7 3.2 PRESENT DISTRIBUTION........................................................................................................................ 8 3.2.1 South Australia ............................................................................................................................. 9 3.2.2 Victoria......................................................................................................................................... 9 3.2.3 New South Wales ........................................................................................................................ 10 3.2.4 Queensland................................................................................................................................. 11 3.2.5 Australian Capital Territory....................................................................................................... 12 3.2.6 Angler survey.............................................................................................................................. 12 3.3 TRANSLOCATIONS .............................................................................................................................. 12 4 CONSERVATION STATUS AND LEGAL PROTECTION............................................................. 14 5 BIOLOGY AND ECOLOGY................................................................................................................ 15 5.1 GROWTH, LONGEVITY AND MATURITY ................................................................................................ 15 5.2 DIET ................................................................................................................................................... 16 5.3 HABITAT PREFERENCE ........................................................................................................................ 17 5.4 MOVEMENT ........................................................................................................................................ 20 5.5 REPRODUCTION .................................................................................................................................. 21 5.5.1 Spawning cues ............................................................................................................................ 21 5.5.2 Spawning behaviour ................................................................................................................... 22 5.5.3 Fecundity and spawning............................................................................................................. 26 5.5.4 Larval growth ............................................................................................................................. 26 5.5.5 Reproductive strategies of other Plotosidae............................................................................... 26 6 CASE STUDIES ...................................................................................................................................... 29 6.1 BARREN BOX SWAMP, NEW SOUTH WALES ........................................................................................ 29 6.2 WIMMERA RIVER, VICTORIA ............................................................................................................... 31 6.3 CARDROSS LAKES, VICTORIA .............................................................................................................. 32 6.4 LAKE VICTORIA, MARYBOROUGH, VICTORIA ..................................................................................... 35 SECTION 2 - REVIEW OF THREATS .................................................................................................. 38 7 RIVER REGULATION.......................................................................................................................... 38 7.1 CHANGES TO FLOW REGIMES .................................................................................................... 38 7.1.1 BACKGROUND .................................................................................................................................. 39 7.1.2 MANAGEMENT ................................................................................................................................. 42 v Freshwater Ecology, NRE & Murray Darling Basin Commission

Freshwater Catfish – A Resource Document 7.1.3 ASSESSMENT OF THE SIGNIFICANCE OF THE THREAT ......................................................................... 43 7.2 CHANGES TO TEMPERATURE REGIMES.................................................................................. 49 7.2.1 BACKGROUND .................................................................................................................................. 49 7.2.2 MANAGEMENT ................................................................................................................................. 52 7.2.3 ASSESSMENT OF THE SIGNIFICANCE OF THE THREAT ........................................................................ 53 7.2.4 INCREASES IN WATER TEMPERATURE .............................................................................................. 56 7.3 BARRIERS ........................................................................................................................................... 57 7.3.1 BACKGROUND .................................................................................................................................. 57 7.3.2 MANAGEMENT ................................................................................................................................. 58 7.3.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT ............................................................................... 63 8 INTRODUCED SPECIES ...................................................................................................................... 67 8.1 CARP..................................................................................................................................................... 67 8.1.1 BACKGROUND .................................................................................................................................. 68 8.1.2 MANAGEMENT ................................................................................................................................. 69 8.1.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT ............................................................................... 70 8.2 REDFIN................................................................................................................................................. 78 8.2.1 BACKGROUND .................................................................................................................................. 78 8.2.2 MANAGEMENT ................................................................................................................................. 79 8.2.2 ASSESSMENT OF SIGNIFICANCE OF THE THREAT ............................................................................... 79 8.3 OTHER INTRODUCED FISH SPECIES ......................................................................................... 82 9 WATER QUALITY ................................................................................................................................ 84 9.1 SEDIMENTATION.............................................................................................................................. 84 9.1.1 BACKGROUND .................................................................................................................................. 85 9.1.2 MANAGEMENT ................................................................................................................................. 86 9.1.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT ............................................................................... 86 9.2 SALINITY............................................................................................................................................. 90 9.2.1 BACKGROUND .................................................................................................................................. 90 9.2.2 MANAGEMENT ................................................................................................................................. 91 9.2.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT ............................................................................... 91 9.3 ALGAL BLOOMS ............................................................................................................................... 95 9.3.1 BACKGROUND .................................................................................................................................. 95 9.3.2 MANAGEMENT ................................................................................................................................. 96 9.3.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT ............................................................................... 97 9.4 AGRICULTURAL CHEMICALS...................................................................................................... 99 9.4.1 BACKGROUND .................................................................................................................................. 99 9.4.2 MANAGEMENT ............................................................................................................................... 100 9.4.3 ASSESSMENT OF THE SIGNIFICANCE OF THE THREAT ...................................................................... 102 10 RIPARIAN VEGETATION ............................................................................................................... 107 10.1 BACKGROUND ................................................................................................................................. 107 10.2 MANAGEMENT ................................................................................................................................ 109 10.3 ASSESSMENT OF THE SIGNIFICANCE OF THE THREAT ....................................................................... 110 Freshwater Ecology, NRE & Murray Darling Basin Commission

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Freshwater Catfish – A Resource Document 11 REMOVAL OF WOODY DEBRIS................................................................................................... 111 11.1 BACKGROUND ................................................................................................................................. 111 11.2 MANAGEMENT ................................................................................................................................ 112 11.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT .............................................................................. 113 12 AQUATIC VEGETATION ................................................................................................................ 115 12.1 BACKGROUND ................................................................................................................................. 115 12.2 MANAGEMENT ................................................................................................................................ 119 12.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT .............................................................................. 119 13 DISEASES............................................................................................................................................ 121 13.1 BACKGROUND ................................................................................................................................. 122 13.2 MANAGEMENT ................................................................................................................................ 126 13.3 ASSESSMENT OF THE SIGNIFICANCE OF THE THREAT ....................................................................... 126 14 AQUACULTURE INDUSTRY, TRANSLOCATIONS AND GENETIC IMPLICATIONS ...... 128 14.1 BACKGROUND ................................................................................................................................. 128 14.2 MANAGEMENT ................................................................................................................................ 134 14.3 ASSESSMENT OF THE SIGNIFICANCE OF THE THREAT ....................................................................... 135 15 COMMERCIAL FISHING ................................................................................................................ 137 15.1 BACKGROUND ................................................................................................................................. 137 15.2 MANAGEMENT ................................................................................................................................ 143 15.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT .............................................................................. 143 16 RECREATIONAL FISHERY............................................................................................................ 146 16.1 BACKGROUND ................................................................................................................................. 146 16.2 MANAGEMENT ................................................................................................................................ 147 16.3 ASSESSMENT OF SIGNIFICANCE OF THE THREAT .............................................................................. 149 17 THREAT ASSESSMENT BY RECOVERY TEAM ....................................................................... 151 18 REFERENCES .................................................................................................................................... 153 19 PERSONAL COMMUNICATIONS ................................................................................................. 184


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Section 1 - Existing Ecological Information 1 Introduction This resource document is separated into two sections. Section 1 includes a description of freshwater catfish, outlines its past and present distribution, its conservation status and legal protection throughout the Murray Darling Basin, as well as our current state of knowledge on aspects of its biology and ecology. Several case studies are provided of sites where abundant populations occur as well as sites where the species has declined significantly. Section 2 provides a review of existing potential threats to the species and its habitat. Each review includes a background to the threat, a discussion of current management as well as an assessment of the significance of each threat to freshwater catfish. Each review provides a summary of each threat. The resource document also includes an initial assessment of the significance of threats undertaken by the recovery team at the commencement of this project. Freshwater catfish is a freshwater fish species which occurs within the Murray Darling Basin as well as the eastern drainages of New South Wales and Queensland. Recent research has indicated that there are a number of as yet undescribed new species and subspecies in coastal areas and further work is required to clarify their distribution. This resource document includes some information on research undertaken on coastal populations, although the associated recovery plan (Clunie and Koehn, in press) relates specifically to the Murray Darling Basin populations. Freshwater catfish was once one of the most common fish species within the Murray Darling Basin. As is the case for many native fish species, detailed information concerning the past and present distribution of freshwater catfish is limited, patchy and often anecdotal. However, it is apparent that the species has experienced a significant decline in distribution and abundance throughout most of its range. This observation comes from a collation of past and present survey data, the views of scientists, fisheries managers and anglers as well as commercial catch information. Declines have been observed in some areas of the Murray Darling Basin such as the upper Murray river since the 1950s, while in many other areas since the late 1970s and 1980s. While reasonable populations still occur in parts of Queensland, the majority of populations in Victoria and New South Wales occur in impoundments with few riverine populations remaining. Queensland represents the stronghold of freshwater catfish and the protection of the species in this state must be seen as a high priority. The collation of existing information of freshwater catfish has indicated that while there has been some targeted research on the species, further research is required to fully understand the species' habitat preferences and requirements, the significance of threats to its aquatic environment, and the reasons for its recent decline in abundance and distribution. Some research has been carried out on reproductive biology, including inducement to spawn in rearing ponds (Lake 1967a), morphogenesis, ontogeny and fecundity (Lake 1967b, Davis 1977a,b), age determination and growth Freshwater Ecology, NRE & Murray Darling Basin Commission

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(Davis 1977c), diet (summarised by Kennard and Pusey 1997), spawning behaviour (Merrick and Midgley 1981, Clunie, unpublished data) and the genetic variation in different populations (Musyl 1990, Jerry 1994, Keenan et al.1994, Musyl and Keenan 1996, Jerry and Woodland 1997). Some research has been undertaken on the habitat use of adults and juveniles in the Mary River in south east Queensland (Kennard and Pusey 1997) as well as in the Tweed River in northern New South Wales by Richardson (1984). Only a limited amount of research has been conducted on the species' movement patterns (Davis 1975, Reynolds 1983, Richardson 1984). Some work has also been undertaken on the presence of the pesticide endosulphan in freshwater catfish (Nowak 1990, Nowak 1992, Nowak and Ahmad 1989, Nowak and Julli 1992). The species has not been a significant aquaculture species in the past and so there has been little written on aquaculture techniques. The vast majority of research has been conducted in New South Wales and Queensland, with little information available from the southern portion of its range.

2 Description D.I,4-6, D+C+A.142 P.I,10 V.I,5 * 2.1 Taxonomy Two families of catfish occur in Australia, the Ariidae (Fork-tailed Catfish) and the Plotosidae (Eel-tailed Catfish). Plotosidae occur throughout the Indian Ocean and western tropical Pacific in freshwater, estuarine and coastal marine habitats (Paxton et al. 1989). While no detailed revision of the Plotosidae has been undertaken, there are currently about eight genera and 30 species recognised, including 16 species provisionally occurring in Australia. There are a number of recognised but undescribed freshwater species in Australia (Paxton et al. 1989). Paxton et al. (1989) list the following genera as occurring in Australian waters: Anodontiglanis, Cnidoglanis, Euristhmus, Neosilurus, Paraplotus, Plotosus, Porchilus and Tandanus. Approximately half of the species from the family Plotosidae occurring in Australia are found in freshwater. Two species of Tandanus are currently formally described; Tandanus bostocki freshwater cobbler occurs in south western Australia, while Tandanus tandanus freshwater catfish occurs within the Murray Darling Basin system and in coastal streams in Queensland and New South Wales. Recent genetic studies have indicated there are a number of species and subspecies of freshwater catfish in coastal areas; these are yet to be formally described (see section 2.2). The freshwater catfish Tandanus tandanus (Mitchell 1838), is a member of the family Plotosidae, and is distinguishable by the tapering appearance of the joined second dorsal, caudal and anal fins. Members of the family also have several pairs of barbels around the mouth, are scaleless and have a smooth tough skin. A single spine is found in the first dorsal fin and the pectoral fins. The freshwater catfish is also known as the eel-tailed catfish, jewfish, tandan or kenaru. It has a stout body, almost circular in section with the posterior of the body compressed. The head is large and flattened below with a blunt rounded snout. The moderately-sized eyes are located high on the *

D=dorsal fins, C=caudal fins, A=anal fins, P=pectoral fins, V=pelvic or ventral fins Freshwater Ecology, NRE & Murray Darling Basin Commission

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side of the head. The downturned mouth has thick fleshy lips and there are eight barbels in four pairs around the mouth. The vomerine teeth are in a semicircular patch. The anterior nostrils are tubular and located on the front border of the upper lip. The first dorsal fin is short based, located high on the back behind the head and preceded by a strong serrated spine. The second dorsal fin combines with the caudal and anal fins to form a continuous median fin. The pectoral fins are large, located low on the body and have strong serrated spines. The pelvic fins are abdominal and rounded (Cadwallader and Backhouse 1983). Plate 2.1 Freshwater catfish Tandanus tandanus

Although colour may vary, fish are usually brown, reddish brown, olive green to grey dorsally and laterally, while lighter to white ventrally (Cadwallader and Backhouse 1983). Fish may have a mottled appearance (Plate 2.1). The species exhibits sexual dimorphism by one year of age, with the female having a triangular urogenital papilla while the male has a cylindrical one (Lake 1967d).


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2.2 Genetics While the freshwater catfish has a wide distribution in Australia, it is only recently that research has been carried out to determine the genetic variation over the taxon’s range. Lake (1971) indicated his surprise in collecting freshwater catfish in the fast flowing Daintree River in northern Queensland, and noted that they were foreshortened and stumpier in appearance compared to southern samples. He suggested this may have been a different species. Merrick and Schmida (1984) noted that northern populations appeared to show some differences in body growth and habitat preferences. Keenan (DPI, pers. comm. 1999) have examined this population and identified many significant genetic differences at 50% of the loci examined, that indicate that they are a different species. Freshwater catfish occur within the Murray Darling Basin, as well as the eastern drainages of New South Wales and Queensland (Plate 2.2). The Great Dividing Range extends along the eastern perimeter of Australia and represents an effective geographic barrier to gene flow (Musyl and Keenan 1996). Rivers to the west of the divide follow a dendritic pattern, while those to the east have patterns arising from a complicated geological history (Ollier 1982). Musyl and Keenan (1996) noted that genetically distinct populations of fish from four genera have been identified from east and west of the Great Dividing Range using allozyme studies. Morphometric and genetic studies have compared freshwater catfish populations within and between the isolated drainage basins where they are found. Populations within the Murray Darling River system and in the eastern drainages of New South Wales and Queensland have been investigated (Musyl 1990, Jerry 1994, Keenan et al. 1996, Musyl and Keenan 1996). Musyl and Keenan (1996) found no apparent morphometric variation, despite using erudite statistical methods, between populations east and west of the Great Dividing Range. Seven polymorphic loci were identified for freshwater catfish. Electrophoretic comparisons showed that there is one species throughout the Murray Darling Basin (the type location for the species) and a subspecies in the Fitzroy River in Queensland, and two different and undescribed species, one in the Nymboida River and the Bellinger River in New South Wales (Musyl 1990, Musyl and Keenan 1996) and the second in the Tully River, north east Queensland (Keenan et al.1994). These studies demonstrated that there was genetic variation not only east and west of the Great Dividing Range, but also between several of the eastern drainages. Ollier (1982) suggested volcanic activity may have separated eastern coastal streams in the Bellinger River, possibly spreading this species into the Clarence River basin. In Musyl’s (1990) and Musyl and Keenan’s (1996) studies, freshwater catfish from the Bellinger River differed the most genetically from all other populations. The higher level of similarity between the populations from the Nymboida River and other Murray Darling populations indicated that there had been genetic exchange in the past (Musyl and Keenan 1996). Jerry and Woodland (1997) note that fish in adjacent river systems had not been investigated and speciation may have occurred in each river system. Jerry (1994) considered catfish from the Bellinger, Macleay, Hastings and Manning Rivers to be an undescribed subspecies of Tandanus tandanus, while those Freshwater Ecology, NRE & Murray Darling Basin Commission

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from the Tweed, Richmond and Clarence Rivers to the north were more closely related to T. tandanus although they showed some genetic isolation. Jerry and Woodland (1997) noted that the relationship between T. tandanus and those fish within the Tweed, Richmond and Clarence Rivers was unclear and required further research. The limited movement of native fish between populations identified between the populations examined in the dammed headwaters of the Murray Darling Basin means that many populations are now isolated from each other, and that recruitment depends on their reproductive capacity (Keenan et al.1996). This may be of particular concern for freshwater catfish, which appear to remain in the same section of river for most of their lives. Genetically isolated populations occur in impoundments along the western slopes of the Great Dividing Range. The rarity of freshwater catfish within the Murray Darling Basin and the reduced number of fish breeding represents a likely reduction in genetic variation (Keenan et al. 1996). Keenan et al. (1996) observed populations in dams and lakes to have lower heterozygosities than populations in rivers, although did not find a significant negative relationship between inbreeding (as measured by fluctuating asymmetry) and heterozygosity in catfish.


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Plate 2.2 The location of catchments in coastal areas of New South Wales and Queensland where new species and subspecies of Tandanus have been identified.


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3 Distribution 3.1 Past Distribution The natural distribution of freshwater catfish includes the Murray Darling River system of South Australia, Victoria, New South Wales and Queensland, as well as the eastern drainages in coastal streams in New South Wales and Queensland. Whitley (1941) incorrectly stated the species occurred in Western Australia. Detailed information concerning the species’ distribution and abundance in the past within the Murray Darling system is limited. Pierce (1988) indicated that the species was previously considered very common in the Murray system. Anecdotal information supports this observation. Over 100 years ago, in New South Wales, Tenison-Woods (1883) observed that freshwater catfish were “… very abundant in the lagoons and backwaters of the western rivers...”. General texts such as Grant (1972) considered freshwater catfish to be one of Queensland’s “... most common freshwater fishes of coastal rivers and streams, inland waterways, dams and reservoirs...”. Roughley (1951) noted that while the species had once “used to swarm” in the Murray River, it was now rare in most parts of this system, although it “.. still persists in considerable numbers in the Darling River and its widespread tributaries in New South Wales and Queensland..”. He suggested that the species had suffered from competition with redfin Perca fluviatilis and carp Cyprinus carpio. Pierce (SARDI, pers. comm. 1998) noted that freshwater catfish was very abundant in South Australia until the mid 1950s, with catches measured in ‘wheatbags full’. While non commercial harvests were previously consistently high, they have not returned to anywhere near previous levels. In New South Wales, Roberts and Sainty (1996) present observations of locals along the Lachlan River demonstrating the value of anecdotal information. These include numerous observations of freshwater catfish being abundant in this river up until about the 1970s/1980s. In 1915, along Bundaburrah Creek, two fishermen, “… landed no less than 81 catfish.” In the 1930s, “...there were heaps and heaps of catfish. They were in the river and creeks, anywhere at all". In the 1970s/1980s, above the Lake Brewster Weir, “... it was just lousy with catfish. Then it tailed off in the ‘80s. Now it is not heard of, catching catfish in that weir pool”. By the 1990s, “I haven’t seen a catfish for years...” and “It is very hard to find catfish nowadays.” A local fisherman, Mr McKenzie recalled that in about 1927, in the Billabong Creek, in New South Wales, “… and the catfish were thick. And don’t tell me they don’t fight! They’re like lightening. Just try a seven pound catfish (3.2kg)” (Trueman and Luker 1983). In the late 1940s/early 1950s, Langtry (in Cadwallader 1977) observed fish as heavy as 3.6kg taken from the Murrumbidgee River, although they were not taken in large numbers. Between Darlington Point and Lachlan River junction “.. catfish (are) rare, only about 2 fish per year being caught in drum nets.” By 1967, the species was apparently absent or rare upstream from Wagga Wagga in the Murrumbidgee River (Lake 1967c). Brown (1994) suggested healthy populations occurred in the Murrumbidgee River until the late 1970s.


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In Victoria, in Lake Mournpoul, now within Hattah Kulkyne National Park, O’Donohue (1915) observed “...numerous large, circular holes...”, which were freshwater catfish nests. Along the Murray River, Langtry (in Cadwallader 1977) observed that in 1949-50, there were large numbers in the Mildura area, particularly in irrigation channels. A local fisherman, Mr McKenzie recalled that in about 1927, “... all the channels around Shepparton were full of ... catfish. ... There were also catfish all the way up to Eildon in the lagoons near the Goulburn. All those were full of catfish” (Trueman and Lucker 1983). By 1983, Cadwallader and Backhouse (1983) still considered the species common in some areas of Victoria, particularly around Mildura. Langtry (in Cadwallader 1977) noted that freshwater catfish were taken frequently in the Lake Victoria district, in the Lindsay River and the Walpolla Creek anabranch systems. However, there have been observations of the species’ scarcity upstream along the Murray. By the early 1950s, Roughley (1951) observed that freshwater catfish had become rare throughout practically the whole length of the Murray River and considered the species almost extinct upstream of the Torrumbarry Weir. Langtry (in Cadwallader 1977) indicated the species was rarely seen upstream of Boundary Bend, east of Robinvale. Further upstream, the species was considered rare or absent upstream of Mulwala (Lake 1967a, Walker and Hillman 1977). Walker (1981) suggested that the effects of Hume Dam and Yarrawonga Weir had displaced species such as freshwater catfish from that part of its former range. By 1983, Cadwallader and Backhouse (1983) noted the species was rare upstream of Echuca. 3.2 Present Distribution The distribution of freshwater catfish has changed since European settlement, due both to the decline in its abundance and distribution, as well as to the translocation of fish into various river systems, impoundments and private dams. It is apparent that freshwater catfish has suffered a significant decline in abundance and distribution from rivers within the Murray Darling Basin. While there have been observations of declines in the upper areas of the Murray River since the 1950s, declines have been described for many areas since the late 1970s and early 1980s. Over 25 years ago, Lake (1971) considered freshwater catfish a species whose distribution and abundance had been considerably reduced. Reynolds (1976) noted the decreasing abundance of common native fish species such as freshwater catfish in the Murray River in South Australia. However, this decline seems quite recent in some areas. In relation to the commercial fishery of this species, Pollard et al. (1980) observed that no decline in populations was currently apparent. Distribution and abundance information must be interpreted with care, taking into account concentration of survey effort, survey methodology (e.g. nets used that may capture or fail to capture particular species, ages or sizes of fish), community composition (e.g. some species may be far more abundant and dominant to catch) and survey focus (e.g. stocking assessments, ecological surveys, presence/absence etc.). Since adult freshwater catfish appear to exhibit limited movements, fish may be less likely to be captured unless surveys are conducted within their home range. Recent surveys in the Murray Darling Basin (Paroo River, Darling River, Murrumbidgee River and Murray River) indicate that freshwater catfish numbers are currently extremely low (Gehrke et al.1996). Gehrke et al. (1996) explained that the species had not yet been recognised as threatened by the Australian Society for Fish Freshwater Ecology, NRE & Murray Darling Basin Commission

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Biology because numbers were sufficiently abundant in impoundments. Keenan et al. (1996) noted that while the species once had a wide distribution in the Murray Darling Basin, it had become rare in many riverine areas. During their study, naturally breeding populations were found in Ewenmar Creek (Macquarie River), Duck Creek (Bogan River), Charleville (Warrego River) and Renmark (Murray River). 3.2.1 South Australia In 1988, Pierce (1988) still considered freshwater catfish common in South Australia, although noting it had declined compared to the past. The population in this state was very low containing few large fish, although he suggested abundance may be cyclic. Pierce (SARDI, pers. comm. 1998) believes the species did decline, although may be recovering to a minor degree. He believes the species can still be caught although it has clearly declined in abundance; where there are old reports of anglers’ catches in terms of wheat bags per day, such takes are now not heard of. The species has been introduced in a number of areas outside the Murray Darling Basin. Pierce (SARDI, pers. comm. 1998) notes that the majority of distribution and abundance information for this species comes from commercial fisheries data, with some other ad hoc observations as well as work by Reynolds. There have been regular surveys in South Australia since 1990 to determine relative abundance indices for freshwater fish species. Pierce (SARDI, pers. comm. 1998) has observed spikes in abundance of freshwater catfish when strong year classes become apparent. 3.2.2 Victoria In Victoria, Cadwallader and Backhouse (1983) noted the species was now rare upstream of Echuca, although common in some areas such as near Mildura. Brumley et al. (1987) observed that there appeared to be the persistence of small populations in the Goulburn River basin. By 1990, Koehn and Morison (1990) recognised the species only had good populations in a few widespread sites. Freshwater catfish has been recorded from nine basins in Victoria. These include six basins where populations naturally occur - Upper Murray, Ovens River, Broken River, Goulburn River, Loddon River, Avoca River, Murray Riverina and the Mallee. Freshwater catfish have been introduced into the other three river basins - the Wimmera, La Trobe and Yarra Rivers. The majority of records are from the Goulburn River, Loddon River, Murray Riverina, Mallee and the Wimmera (DNRE, Freshwater Ecology Database). In Victoria, no surveys have specifically been undertaken to assess the distribution and abundance of freshwater catfish. Therefore, available information comes from a variety of Departmental surveys as well as miscellaneous records. These include Langtry’s surveys of the Murray in 1949/52, surveys around Shepparton during the carp project (Hume et al. 1983), surveys of northern Victoria by Brumley et al. (1987) to assess the conservation status of native species, surveys by Departmental staff at Kaiela and Snobs Creek, surveys of the Wimmera River (e.g. Anderson and Morison 1989), angling club data, and inland angling information compiled by Tunbridge and Rogan (1976), Tunbridge and Rogan (1981) and Tunbridge, Rogan and Barnham (1991). There have also been a number of recent surveys in the Cardross Lakes near Mildura. Freshwater catfish have consistently been collected during all five surveys with a range of size classes indicating successful recruitment (Raadik and Fairbrother 1999). Freshwater catfish also appear to occur in reasonable numbers in the Little Freshwater Ecology, NRE & Murray Darling Basin Commission

9


Murray River. Self-sustaining populations occur in the Wimmera River and Richardson River where the species has been introduced. There are a few other significant populations in small lakes in Victoria. Freshwater catfish are occasionally recorded within the Goulburn River system. 3.2.3 New South Wales When determining the appropriate location of a fishway on the Murray River near Mildura, Thorncraft and Mallen-Cooper (1992) surveyed fish below the Mildura Weir and Loch and did not record freshwater catfish. During an extensive assessment of the Torrumbarry fishway on the Murray River between 1990 and 1992, Mallen-Cooper et al. (1995) only recorded one freshwater catfish. Mallen-Cooper and Brand (1992) recorded the species at Murtho on the Murray River (Loch 6) when assessing the effectiveness of that fishway. Brown (1994a) surveyed Gol Gol Swamp near Mildura and failed to record freshwater catfish. During three surveys to investigate fish movement through weirs on the Darling River, very low numbers or no freshwater catfish were recorded; at Menindee Weir (Mallen-Cooper and Edwards 1991), Bourke Weir (Harris et al. 1992) and Brewarrina Weir (Mallen-Cooper and Thorncroft 1992). Thorncraft and Harris (1996) assessed the effectiveness of rock ramp fishways on the Goondiwindi Weir and the Macintyre River and weirs on the Bell River near the junction with the Macquarie River. A total of four freshwater catfish were recorded at the Goondiwindi Weir fishway and two at the Bell River fishway. There have been surveys of the Severn and Macintyre rivers in the area of Pindari Dam; survey sites included regulated sites where the flow regime was determined largely by water releases and control sites where flow was determined by more natural events e.g. tributary input. Freshwater catfish was one of the main species recorded at most regulated sites (Swales and Curran 1995). A range of size classes were present indicating the likelihood of breeding. Swales and Curran (1995) noted that the species appeared to be more numerous in earlier surveys of the area where it had been the dominant large native fish species at most sites. They suggested that this result was either because of an actual change in the species abundance, or due to the relative selectivities of different survey techniques. During their surveys it became apparent that the efficiency of using an electrofishing boat for such a benthic species may have been limited and so fyke nets were then included in the survey. Brown (1994) observed that healthy populations were common in the Murrumbidgee River until the late 1970s, although it was now difficult to find populations in rivers. A survey of Cudgegong River between Windamere and Burrendong Dams recorded small numbers of freshwater catfish (Swales et al. 1993). Swales et al. (1993) noted this section of river was severely degraded and had an impoverished fish fauna. Swales and Curran (1995) carried out a fish survey of the Macquarie River and its tributaries in the area of the Macquarie Marshes. No freshwater catfish were recorded. While another earlier survey in 1989 also failed to record freshwater catfish, previous surveys carried out in 1979 and 1992 recorded low numbers of the species. While Swales and Curran (1995) noted that many of these surveys have been limited, the absence of freshwater catfish from the recent survey may indicate a decline. Callanan (1984) surveyed five sites on the Darling River anabranch. No freshwater catfish were collected, although they had been previously recorded in the area. At the Freshwater Ecology, NRE & Murray Darling Basin Commission

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time, a fisheries inspector indicated the species used to be quite common but had become almost non existent in the commercial catches in recent times. Callanan (1985) surveyed a number of sites on the Darling, Barwon, Warrego, Gwydir and Paroo rivers. No freshwater catfish were collected. Llewellyn (1983) outlined the distribution of fish species in New South Wales, collating museum records, his own records as well as the results of an extensive survey. He considered freshwater catfish to be “common” in central New South Wales and the north-eastern region including coastal streams, although not present in cooler waters. The recent New South Wales Rivers survey (Harris and Gehrke 1997) sampled 80 sites four times over a two year period using a range of fishing techniques. No freshwater catfish were recorded from the Murray region, while 58 were recorded in the Darling region, 488 in the North Coast region and one from the South Coast region. In the Darling region, freshwater catfish were collected in the Namoi River near Boggabri (three fish), the Macquarie River and the Little River near Wellington (18 fish), the Turan River near Sofala (20 fish), the Talbragar River near Dunedoo (eight fish), the Horton River near Upper Horton (nine fish) and the Bogan River near Nyngan (one fish). Gehrke et al.(1996) surveyed nursery habitats in the Paroo catchment, the Darling River near Menindee, the Murrumbidgee River near Narrandera and the Murray River in the Millewa area. Of more than 11 000 fish caught, no freshwater catfish were recorded. 3.2.4 Queensland Few surveys have been undertaken in Queensland on the distribution and abundance of freshwater fish in the Murray Darling Basin. Most records are from surveys by Turner and Pollard in 1976, Midgely in 1989, as well as miscellaneous surveys by Wager, the Australian New Guinea Fishes Association and Leggett. Midgely (1989) surveyed areas within the Lake Eyre and Bullo River systems, as well as areas within the Murray Darling Basin such as the Warrego, Condamine and Balonne rivers. Freshwater catfish was considered abundant at sites along the Merivale River (near Mitchell) and the Balonne River (near St George), common along the Condamine River (near Condamine) and the Warrego River (near Charleville) and rare along the Warrego River (near Cunnamulla). Midgely (1989) also noted that while he did not record freshwater catfish at Macintyre Brook near Inglewood, locals indicated the species was present. A recent survey of landholders was undertaken in southern Queensland and northern New South Wales seeking opinions concerning changes to the natural environment, including perceived declines in fish numbers (Mottell 1995). Table 3.1 summarises opinions provided concerning freshwater catfish. The survey indicates a clear trend, with a significant proportion of landholders believing the species has either declined or is non existent in the rivers under investigation.


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Table 3.1 Landholder opinions of the status of freshwater catfish (taken from Mottell 1995) River Barwon Birrie Bokhara Culgoa Narran

Year Seen 1994 1994 1990 1994 1993

Last Abundant

7

Common

In Decline

6 3 7 18

15 11 11 23 39

Non Existent 2 7 7 10 17

In Queensland, Moffatt (DNR, pers. comm. 1998) notes that freshwater catfish are abundant in many areas, particularly the Condamine-Balonne and Border River catchments. Moffatt (DNR, pers. comm. 1998) believes that abundance appears to have declined dramatically in some regions, such as within the Paroo catchment. 3.2.5 Australian Capital Territory The distribution of freshwater catfish was recently reviewed by Lintermans (2000). The species is not native to the Canberra region and there have been unconfirmed angler records from the Queanbeyan River below Queanbeyan. There have been a number of stockings of farm dams, lakes and ponds some of which have been successful. There were unsuccessful stockings of Lake Burley Griffin and Lake Ginninderra in the late 1970s. 3.2.6 Angler survey As part of this project, an angler survey was undertaken within the Murray Darling Basin. The results of this survey are discussed in detail in Northey and Clunie (in press). While the survey was only a minor component of the project, it provided valuable information concerning the past and present distribution of freshwater catfish. Records of catches were provided from a wide range of sites within the Murray Darling Basin, however there was some concentrations of records. These included areas where reasonable populations were already believed to occur, such as the Murray River primarily downstream of Swan Hill, the Little Murray River and the Wimmera River in Victoria and the Condamine-Balonne catchment in Queensland. 3.3 Translocations There have been a number of introductions and translocations of hatchery-reared freshwater catfish as well as the translocation of wild fish. Queensland The Recreational Fisheries Enhancement Program commenced in 1986/87 (Wager 1994). Hogan (1995) indicated freshwater catfish have been released in Barron River system, Lake Tinaroo impoundment (established, low numbers), Freshwater Creek, Lake Morris impoundment (new population established) and North Johnstone River, Millaa Millaa above falls (new population established). McKay (1989) indicated that freshwater catfish had been translocated to Beatrice River, Lake Morris and Lake Freshwater Ecology, NRE & Murray Darling Basin Commission

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Tinaroo from Enoggera Dam in southern Queensland. Seven hundred fish were produced at the Walamin hatchery in 1984/85 as a result of natural pond breeding and released “...to streams on the upper Atherton Tableland.” (Fisheries Research Branch 1985). Fish were also possibly stocked from the Murray Darling Basin into the Brisbane River at the turn of the century. Moffatt (DNR, pers. comm. 1998) notes that freshwater catfish have apparently been transferred from the Warrego River to the Paroo River by locals because of concern over their decline in the Paroo River. New South Wales Pollard et al. (1996) indicate that while freshwater catfish in coastal rivers from the Manning River northward are likely to be native to the eastern drainages, populations in the Hawkesbury and Hunter rivers are likely to have originated from stocks translocated from tributaries of Murray Darling system. Harris and Battaglene (1989) indicated that freshwater catfish from the Macquarie River were released into the Hawkesbury River, while fish from Lake Keepit on the Namoi River were released into the Hunter River. Musyl and Keenan (1996) indicated that freshwater catfish have been translocated from Keepit Dam on the Namoi River to Glenbawn Dam. There was genetic evidence that populations in the Hawkesbury, Hunter and Brisbane rivers were introduced from the Murray Darling system (Keenan et al.1994). New South Wales annual reports from 1915 to 1919 refer to the “rescue and transplantation” of freshwater catfish from flooded river flats into dams and rivers. Fish were moved from the Murrumbidgee River flats to Burrinjuck Reservoir (1919) and Temora Demonstration Farm Dam (1919), from flooded land near Bingagee into the Murrumbidgee River (1919), from the Murrumbidgee River into the Nepean River near Penrith and at Wallacia and Cataract Reservoir and Observation Ponds at Prospect (1916), and more general observations of moving fish from the Murrumbidgee river flats which were then “liberated into permanent waters” (1918). Rowland (1995) notes that since the 1980s, a private hatchery has been stocking the Macintyre River with freshwater catfish, as well as golden perch Macquaria ambigua and Murray cod Maccullochella peelii peelii. There have been recent stockings of freshwater catfish into Billabong Creek (J. Lieschke, DNRE, pers. comm. 1999). ACT Freshwater catfish were stocked in Lake Ginninderra and Lake Burley Griffin between 1978 and 1980 although these stockings were unsuccessful (Lintermans 2000). Victoria Freshwater catfish have been introduced outside their natural range, into the Wimmera River. In the 1970s, 600 fish from the Murray River were stocked downstream of Dimboola by the Dimboola Angling Club, about 60 fish were moved from there to Horsham in 1981 by the Horsham Angling Club (Brumley et al. 1987), 1000 fish at Horsham in 1979 and an unknown number at Antwerp (Anderson and Morison 1989). The species appears to have established self-sustaining populations in some areas and are most abundant in the lower reaches of the river. Numbers caught by anglers can vary markedly (Anderson and Morison 1989). Freshwater catfish have also been stocked in Lake Victoria and Goldfields Reservoir near Maryborough. In 1998, 340 small fish (up to about 20 cm) were released in the Castlemaine Botanic Gardens and the Golden Point Reservoir by the Castlemaine Angling Club; these fish Freshwater Ecology, NRE & Murray Darling Basin Commission

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were originally from Barren Box Swamp stocks. Trial releases of freshwater catfish have been recently undertaken in several other small reservoirs in central Victoria. Fish have been stocked in a number of town lakes including Kialla Lake in Shepparton and the Chiltern town dam. There are also individual records of fish from the Yarra River at Diamond Creek and the Moe River. South Australia Freshwater catfish have been stocked in a number of areas outside the Murray Darling Basin. Some fish have been obtained from hatcheries such as the Grong Grong in New South Wales and placed in farm dams for put and take fishing. Introductions include into the Torrens River (permanent population), possibly the upper Broughton (no evidence of successful reproduction), the upper Light River and the upper Wakefield River (permanent). Pierce (SARDI, pers. comm. 1998) is not aware of records of the species from the Eyre or Yorke Peninsulas.

4 Conservation Status and Legal Protection Over 25 years ago, Lake (1971) classified freshwater catfish as a species whose distribution and/or abundance had been considerably reduced. In 1991, Lloyd et al. (1991) considered freshwater catfish to be ‘vulnerable’ within the Murray Darling system. However, with the exception of a new as yet undescribed species, Tandanus n. sp. Bellinger River tandan whose status is considered ‘uncertain’ (ASFB 1999), freshwater catfish do not have a formal threatened classification in Australia. Gehrke et al. (1996) indicated the species is not formally recognised as threatened because it still occurs in sufficient numbers in impoundments. This classification should be reassessed. The freshwater catfish has been classified as 'vulnerable' in Victoria since 1990 (Koehn and Morison 1990, NRE 1999) and has been listed under the Flora and Fauna Guarantee Act 1988. It had previously been classified as 'indeterminate, possibly threatened' (Cadwallader et al. 1984). The species was considered ‘common/secure’ in Queensland in 1993 (Wager 1993). There is no specific formal classification system within New South Wales or South Australia for native freshwater fish species. Commercial fishing In New South Wales, commercial fishermen introduced a voluntary ban on commercial landing of freshwater catfish in 1993. In South Australia, many commercial fishermen have been voluntarily releasing freshwater catfish for around ten years. In 1997, freshwater catfish was declared a protected fish in South Australia by regulations under the Fisheries Act 1982. In Victoria, freshwater catfish has been listed under the Flora and Fauna Guarantee Act 1988 meaning that the species cannot be taken without a permit. There is no commercial fishing industry for freshwater fish species in Queensland. Recreational fishing Table 4.1 outlines recreational fishing regulations within states in the Murray Darling Basin. Regulations are currently being considered in Victoria including closed seasons, bag limits and minimum size limits. Freshwater Ecology, NRE & Murray Darling Basin Commission

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Table 4.1 Recreational fishing regulation for freshwater catfish

State Queensland

Size Limit (cm) 35

New South Wales

30

Victoria

30

South Australia

Fully protected

Bag Limit • Combined total of 5 fish in genera Tandanus and Neosilurus (within MDB) • Combined total of 10 fish in genera Tandanus and Neosilurus (outside MDB) • Two fish (streams) • Five fish (impoundments) • Bag limit of 2 in all waters within the Wimmera Basin • No take from any other waters in Victoria Fully protected

5 Biology and Ecology The following information on the biology and ecology of freshwater catfish is summarised at the end of this section (Table 5.1) 5.1 Growth, longevity and maturity Freshwater catfish may grow to about 915 mm in length and weigh 6.8 kg, although the majority caught weigh between about 0.9 kg and 1.8 kg (Lake 1959). Blandowski (1857) indicated freshwater catfish may weigh between 3.2 and 3.6 kg (7 to 8 lb) and grow to 620 mm (2 feet). In his study of freshwater catfish in the Gwydir River, Davis (1977c) indicated the largest fish of 666 captured measured 574 mm and weighed 2.7 kg. While longevity is unknown, Davis (1977b) recorded fish in nine consecutive year classes. Davis (1977c) used dorsal spines for age determination of freshwater catfish, with validation using fish of known ages and tagging information. Males and females showed no differences in growth rates. Anderson (1990) noted the first year’s annuli may become difficult to detect or may be lost as the core of the spine hollows over time. Otoliths are commonly used to age fish for annual and daily increment determinations (Anderson 1990). The central ageing facility at Queenscliff in Victoria currently uses both otoliths and dorsal spines to age freshwater catfish. Recent ageing of four fish using both techniques indicated variable results, and suggested that using otoliths may be the most reliable ageing technique. The following estimates of age were obtained using otoliths and spines respectively; 12 years (six years), five years (four years), five years (four years) and four years (four years) (T. Raadik, DNRE, pers. comm. 1998). Sedger (1994) aged freshwater catfish from the Nymboida and Orara rivers, subcatchments of the Clarence River on the coast in northern New South Wales. Using dorsal spines, the maximum ages were 11-12 years. Significant differences in growth curves and length at age for two, seven and eight year olds were recorded for Freshwater Ecology, NRE & Murray Darling Basin Commission

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fish from the Nymboida and Gwydir rivers. It was suggested this could have been due to genetic and environmental differences or a combination of both.. Significant differences were also recorded from fish in the Orara River growing at a slower rate compared to those in the Nymboida River; it was suggested that the Nymboida River could support larger populations of fish having larger deeper pools compared to the Orara River. Freshwater catfish in the Gwydir River in New South Wales reached maturity at between 3 and 5 years of age (Davis 1977b). Davis (1977b) observed all fish to have reached maturity by five years and a weight of 1.2 kg, although females could mature at an earlier age and at a lower weight to males. In the Nymboida River, Sedger (1994) estimated age of maturity for both sexes to be five years, at a weight of 1.25 kg and length of 460 mm. Males reached maturity at a smaller length of 430 mm. Interestingly, female fish measuring only about 150 mm and weighing 50-80 g were found to contain eggs in a small overcrowded dam in New South Wales (Pam and Jeff Norman, Hay, pers. comm. 1999). 5.2 Diet Freshwater catfish lack a specialised alimentary canal and do not have a true stomach. The lack of a stomach and an intestinal bulb may not be significant since freshwater catfish have a larger than expected intestine which can accommodate food items that are taken (McMahon 1982). Ingested food does not usually appear to be broken down mechanically; the teeth are small and not well developed and the gill rakers are not highly modified to crush or grasp objects (Davis 1977d). McMahon (1982) noted the species had a number of anatomical features which suggested specialisation for a benthic habit; the broad, flattened head, inferior slit-like mouth bordered by fleshy lips, existence of barbels and fleshy gill rakers. Food location may be assisted by the high density of sensory papillae around the head and mouth. Lake (1967c) suggested that freshwater catfish may be assisted in feeding more by smell than sight; ponds in which they are found can become very muddy. Fallu (1993) notes that they may use their barbels as the main sense organ instead of their eyes in muddy water. Freshwater catfish have primarily been considered carnivorous bottom feeders, with benthic organisms the major aquatic component of their diet. Pierce (1997) however notes that freshwater catfish can move throughout the water column at night where they feed actively. Grant (1978) indicated the species primarily feeds on shrimps, crayfish and aquatic insects, noting that Corbiculinid mussels which are found partially buried in sand were a particular favourite in coastal and western rivers. Davis (1977d) studied the diet of freshwater catfish in the Gwydir River, an upper tributary of the Darling River, before and during inundation of this river by the Copeton Dam. Davis (1977d) considered the species an opportunistic carnivore, using a wide range of food sources, both digging around in substrate for small prey and foraging for large items in the open. Prey included fish, decapods, chironomids, and other miscellaneous aquatic invertebrates. Some variation in diet was observed with age and size of fish, as well as seasonally. Larger fish tended to eat larger prey. Sedger (1994) investigated the diet of freshwater catfish in the Nymboida and Orara rivers in coastal northern New South Wales. The most important food items by percentage were bivalves, followed by gastropods, dragonfly nymphs and polychaete worms. The composition of diet was highly seasonal; in summer bivalves were predominant, while food items Freshwater Ecology, NRE & Murray Darling Basin Commission

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were slightly more diverse in winter. Smaller sized fish primarily ate gastropods and bivalves, while larger fish feed on a greater variety. The stomach contents of three freshwater catfish from Lake Victoria in Victoria contained damselfly and dragonfly larvae, decapods, snails and a small terrestrial insect (J. Lieschke, DNRE, pers. comm. 1999). Pusey et al. (1995) observed some separation between age classes on the basis of prey size in one river in Queensland. Davis (1977d) noted that the presence of crayfish in the diet may indicate that freshwater catfish are not as sluggish in their feeding behaviour as perceived, and that they can be active and powerful predators. It is apparently unusual for a catfish species to feed on fish. In aquarium trials, Pierce (SARDI, pers. comm. 1998) observed that adult freshwater catfish strongly favoured yabbies, moving large rocks to get to this prey. He observed the species was not necessarily being entirely benthic, and moving higher up in the water during the night, to search for prey wherever it is available. In his aquarium trials, Pierce (SARDI, pers. comm. 1998) observed 75-100 mm freshwater catfish to consistently bury themselves during the day, and move out of substrate at night to attack other species. Kennard and Pusey (1997) collated information on the diet of the freshwater catfish from seven studies in Queensland and northern New South Wales. They observed that aquatic insects made up about 40% of the diet, detritus, molluscs and macrocrustacea about 10-15% each, followed by smaller proportions of terrestrial and planktonic invertebrates, terrestrial and aquatic vegetation and algae, fish, as well as unidentified material (Kennard and Pusey 1997). Arthington et al. (1993) investigated the diet of freshwater catfish in a dam near Brisbane. There was a low seasonal variation in diet composition, although there was a clear change following a rise in water level; the amount of detritus increased greatly, terrestrial vegetation was eaten and aquatic invertebrates were eaten less. It is not clear whether freshwater catfish actively feed on detritus or ingest it incidentally due to the species’ benthic foraging habit (Arthington et al. 1992). Arthington et al. (1992) suggest that diets may vary according to differences between areas. For example, in Barambah Creek in Queensland, they classified the species as a detritivore/herbivore, while other work has classified it as a carnivore. In a study of freshwater catfish in the Brisbane River, Queensland, McMahon (1982) indicated that while algal filaments were recorded quite frequently, he did not know whether they were an important part of the diet or whether they were ingested incidentally. 5.3 Habitat preference The species is found in a range of habitat types such as rivers, creeks, lakes and billabongs (Cadwallader and Backhouse 1983). While fish are apparently more abundant in lakes and backwaters (Lake 1967c), the species does inhabit and spawn in flowing streams (Merrick and Schmida 1984). Pollard et al. (1980) indicated that the species generally prefers lakes and sluggish rivers. In a survey in northern Victoria, Brumley et al. (1987) recorded freshwater catfish only in standing waters such as lakes where turbidity was low and macrophytes abundant. However, Llewellyn (1983) indicated the species was found in lakes and sluggish turbid streams with fringing vegetation in New South Wales. Llewellyn (1983) noted freshwater catfish did not occur in cool waters in New South Wales. Freshwater Ecology, NRE & Murray Darling Basin Commission

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It is not known whether habitat preferences vary between freshwater catfish in coastal areas and the Murray Darling Basin. Hogan (DPI, pers. comm. 2000) believes the freshwater catfish in coastal northern Queensland prefer faster flowing water. Some work has been carried out on the habitat preference of freshwater catfish in Mary River in south east Queensland (Kennard and Pusey 1997) and in the Tweed River in northern New South Wales (Richardson 1984). Kennard and Pusey (1997) observed that adults and juveniles tended to occur primarily in sand, fine gravel, gravel and cobbles (between 15-30% each), and much more rarely amongst mud, rocks and bedrock (around less than 5% each). Adults were most frequently recorded in undercut banks and root masses (around 20% each), followed by amongst macrophytes, filamentous algae, leaf litter and large woody debris (around 10% each), to a much lesser extent amongst small woody debris, overhanging vegetation, submerged vegetation (around 5% each) and very rarely in open water and emergent vegetation. Juveniles were most frequently found amongst macrophytes, filamentous algae and leaf litter (between 15-20% each), followed by substrate, submerged vegetation, overhanging vegetation, large and small woody debris, undercut banks and root masses (between 5-10% each) (Kennard and Pusey 1997). Pierce (SARDI, pers. comm. 1998) believes aquatic vegetation is important for freshwater catfish, with more consistent numbers taken in areas of South Australia when aquatic vegetation is present. He and commercial fishers have observed the species to occur around willows or some form of structure and along riverbanks off the bottom at night. Pierce (SARDI, pers. comm. 1998) suggests freshwater catfish move out of backwater habitats after the first year. More juveniles seemed to be found where there was more structure available. Adults did not appear to be found in high numbers in smaller, shallower backwaters and permanent billabongs with no aquatic vegetation. In Victoria, freshwater catfish occur in high densities in a small lake in Maryborough, where they are known to breed successfully. This lake is shallow, primarily up to 1.52m with some deeper holes. The majority of the lake is covered with Ribbonweed Vallisneria gigantea and some Pondweed Potamogeton spp., with Stonewort Nitella sp. found in shallow areas, and some clear channels (Plates 4.1 and 4.2). There is a hard substrate, with a covering of stones, gravel and silt. Cardross Lakes in north west Victoria, which also supports a healthy population of freshwater catfish, has abundant aquatic vegetation primarily Sea Tassel Ruppia megacarpa with emergent Cumbungi Typha sp. and Spike Rush Juncus acutus.


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Plate 4.1 Ribbonweed in Lake Victoria

Plate 4.2 Stonewort in Lake Victoria

A small dam near Hay in New South Wales which contains large numbers of freshwater catfish has abundant aquatic vegetation including Sago Pondweed Potamogeton tricarinatus, with smaller amounts of Red Milfoil Myriophyllum verrucosum, Water Couch Paspalum paspaloides, Austral Water-Mat Lepilaena australis, Stonewort, Water Ribbons Triglochin spp. and Sedge Carex spp (Plate 4.3)


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Plate 4.3 Aquatic vegetation in Hay dam.

In Queensland rivers, Kennard and Pusey (1997) note that freshwater catfish are most frequently found in areas of zero to moderate water velocity. While adults were more often recorded in deeper pools, juveniles and sub adults were more often found in runs. Moffatt (DNR, pers. comm. 1998) observed that in Queensland, freshwater catfish are most abundant above 300 m elevation and are typically found in streams of moderate to low turbidity with coarse substrates. Juveniles are commonly found at high elevations (e.g. >600 m). Some areas where freshwater catfish still occurs in reasonable numbers in parts of southern Queensland are quite turbid with little or no aquatic vegetation. Thus the significance of aquatic vegetation as a habitat component to the species is not clear and requires further investigation. 5.4 Movement While small fish may form loose schools, adults tend to be solitary when they are not breeding (Cadwallader and Backhouse 1983). Recent surveys in the Mary River in Queensland recorded mean and maximum densities of 0.024 and 0.165 fish/m2 respectively (n=215 sites), and mean and maximum biomass of 2.4 and 24.2 g/m2 respectively (n=89 sites) (Kennard and Pusey 1997). Adult freshwater catfish are apparently non-migratory, exhibiting limited movements and tending to remain in the same section of river for most of their lives (Davis 1977c). Merrick and Schmida (1984) noted most individuals move less than 5 km. Davis (1975) tagged 47 fish, and found that the majority returned to within 100m of where they were originally caught, and appeared to be able to return to their “home range” if they had been moved. Following inundation of the Gwydir River, fish moved onto shallow floodplains. During a tagging program on the Murray River, of 425 tagged, 85 fish (20%) were recaptured (Reynolds 1983); 60% (21 fish) had not moved from the area, while 37% (13 fish) moved less than 10 km up or downstream, and only one moved further than 10 km. During a low flow period, fish moved an average of 2 km upstream and 3.6 km downstream, with maximum distances travelled Freshwater Ecology, NRE & Murray Darling Basin Commission

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4 km and 8 km. In the Tweed River, northern New South Wales, Richardson (1984) tagged 144 fish and recaptured 11. About six months after release, none had moved more than about 50 m, and Richardson (1984) suggested the species had a small home range. Reynolds (1983) suggested that freshwater catfish may have a similar movement pattern to carp, with juveniles dispersing from the adult habitat to colonise adjoining areas. Kennard and Pusey (1997) collected juveniles in drift nets set overnight downstream of a riffle area which was at least 100 m from the nearest nest. Moffatt (DNR, pers. comm. 1998) believes juveniles may be quite mobile. Grant (1987) indicated freshwater catfish preferred deeper water during the day, although fish moved into the shallows along banks on moonless nights. Davis (1975) observed adults to be mainly active at night, particularly around dusk and early evening. Fish apparently began to move in the late afternoon, with peaks in activity from dusk to three or four hours later and a steady decline in activity until it ceased soon after sunrise. Recent electrofishing surveys in Victoria have also observed higher levels of activity after dark. During the day, fish were difficult to locate, apparently being well hidden within aquatic vegetation or muddy gravely substrate. During the night, fish seemed to become more active, moving into open areas, probably to feed (D. Harrington, formerly DNRE, pers. comm. 1998). During the breeding season fish have been observed protecting nests through daylight hours. Preliminary trials have been undertaken to develop suitable radiotracking techniques for freshwater catfish (DNRE, unpubl. data.). While these trials only involved a small number of animals in a lake environment and some initial difficulties where encountered, a promising technique has been identified. Future radiotracking of freshwater catfish in a riverine environment would enable clarification of movement patterns. Radiotracking was been used successfully on other species including Murray cod, trout cod Maccullochella macquariensis, golden perch and carp (Koehn and Nichol 1998). 5.5 Reproduction 5.5.1 Spawning cues Freshwater catfish spawn in spring and summer with rises in water temperature. While Merrick and Schmida (1984) noted spawning has been recorded from late October to January over the species’ range, Davis (1977b) recorded spawning in the Gwydir River to occur from January to the end of March. In Barambah Creek in south-eastern Queensland, Arthington et al. (1992) observed a protracted breeding season, with running ripe and spent females recorded from October to March, with a few such fish in April. It has been stated that nest building and spawning does not occur until the water temperature reaches 24oC (Lake 1967a, Davis 1977b). However, Raadik (DNRE, pers. comm. 1999) has observed running ripe males at water temperatures of 18oC at Cardross Lakes near Mildura in mid November. Freshwater catfish were also observed on nests in a lake in Maryborough, Victoria in late October when bottom temperatures were 13.8oC, although it is unlikely that they had commenced spawning at this time (Clunie, pers. obs.). Subsequent monitoring of the lake the next season again indicated nests began appearing in October, although eggs were not recorded on Freshwater Ecology, NRE & Murray Darling Basin Commission

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nests until late November. Water temperatures can fluctuate dramatically in the lake over a period of a day, however, the first eggs recorded appeared to have been laid when water temperatures were about 21oC. Over a breeding season in the lake in Maryborough, eggs were recorded on nests where water temperatures on the nests ranging from 21 and 28.6oC (Clunie, pers. obs.). Davis (1977b) suggested that temperature increases probably directly influence gonad maturation, and indirectly result in an increased food supply. Rising water levels may hasten spawning, although they are not a necessary trigger (Lake 1967a). If water levels are lowered, fish tend to abandon nests and may built another nest; however repeated exposure of nests prevents spawning (Lake 1967a). Davis (1977b) suggested that while freshwater catfish do not require flooding for spawning, they are likely to have evolved breeding habits that enable maximum survival of their young during these unpredictable events. Spawning may occur in flooded and shallow areas of large rivers or quieter backwaters, as well as in farm dams. The species breeds successfully in many farm dams and large impoundments. 5.5.2 Spawning behaviour While it has generally been stated that nest building occurs 1-2 weeks prior to spawning, observations in a lake in Maryborough, Victoria suggest they may be built up to a month before. Lake (1967c) indicated it is unknown whether females or males build the nests. However, in 1915, Mr Anderson, a fisheries officer in New South Wales, provided an early observation of breeding behaviour (NSW Fisheries 1915). He noted that a male fish will make a saucer shaped nest, covering the bottom with sticks and stones. He will move off in search of a mate, and on their return he forces the female into the nest. The male swims beside the female, and their bodies quiver. Once the female deposits the eggs, she leaves, and the male remains by the nest. The male swims around the nest, chasing away small fish that come near, and removing unwanted debris that may enter the nest. These observations are similar to later descriptions. Rougley (1951) noted the recollections of a Mr Hill who had observed males carrying material to the nest “… for distances up to quarter of a mile”. Merrick and Midgley (1981) observed courtship behaviour, with fish weaving and circling the nest. While the nest is usually tended by the male, protection by both adults has been observed in ponds (Merrick and Midgley 1981). Limited electrofishing of fish on nests in a lake in Maryborough indicated males were guarding nests. Fish move over the nest, fanning and protecting eggs (Lake 1967a) (Plate 5.1). Fanning of eggs may result in them moving into more protected cover (Merrick and Midgely 1981).


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Plate 5.1 Freshwater catfish protecting a nest

A recent observation by an angler indicates that nest protection can be strong (Brennon 1997). When a lure was dragged past a freshwater catfish sitting on a gravel bed, it “... made a savage lunge, bumping the lure vigorously, then turning away to take up station back on the gravel bed.” Each time the lure moved past, the fish would race out and chase it away. Brennan (1997) was convinced that the freshwater catfish was “... striking out of pure aggression rather than hunger.” Freshwater catfish build circular to oval nests usually 0.6 to 2 m in diameter and made of coarse sand or gravel, with a central sandy depression (Allen 1989, Pollard et al. 1996). Merrick and Midgley (1981) noted that many nests in Queensland coastal streams had diameters less than 0.7 m. Rougley (1951) observed fish to swim in circles stirring up mud to form a depression, in which they deposited gravel and small sticks. In spawning inducement experiments in artificial ponds, Lake (1967a) observed that when gravel is not present, fish may use other material such as stones and hard earth. He recorded few young in ponds lacking gravel. While nests from the Murray Darling Basin are usually circular, Musyl and Keenan (1996) observed 93% of nests from Bellinger River on coastal New South Wales to be “U” shaped. Larger fish make larger nests. Nests may be used in consecutive years although it is unknown whether by the same pair (Merrick and Midgely 1981). Lake (1967c) noted records of spawning where nests were not constructed and eggs were laid on gravel. Nesting activity in a small lake in Maryborough, Victoria was monitored over the 1998/99 breeding season. Approximately 70 nests were recorded in the 3-4 ha lake. During winter, a small number of circular, relatively cleared areas were apparent. There were a variety of areas which appeared to have possibly been nests which had grown over with vegetation and silt. As the water level dropped over spring and summer, obvious nests began to appear; some were in cleared areas which were obviously cleaned up by the fish, while others were newly established areas. Ongoing observations enabled many nests to be classed in terms of the stage of readiness for spawning. At the point of spawning, the nests were extremely clean and well Freshwater Ecology, NRE & Murray Darling Basin Commission

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maintained by the fish. These nests ranged widely in their appearance from between 0.5 and 2 m in diameter, although many were not entirely circular and the exact boundaries were often difficult to distinguish. The majority of nests consisted on a central depression of coarser gravel and rocks, with fine material around the perimeter; this may settle around the perimeter as a result of the fish fanning and cleaning the area (Plate 5.2 and Plate 5.3). Many nests had sticks or rubbish such as cans and bottles within the centre area. Nests varied from being in obvious depressions to relatively flat areas. Interestingly not all nests were cleared of all vegetation nor consisted of gravel and stones. Some were slight depressions, largely consisting of stonewort with small central areas that were often cleared to only a small degree (Plate 5.4). These areas may not have been identified as nests, except strong site fidelity was observed for a number of fish and several nests were sampled for eggs and larvae. The majority of nests were recorded in less that 1 m of water, with one nest in only 0.35 m of water and one in 1.6 m of water. Further research is required over the next breeding season to determine whether nests are made in the deeper parts of the lake; these were difficult to see due to high algal growth later in the season. Plate 5.2 Freshwater catfish nest


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Plate 5.3 Freshwater catfish nest (note finer material at periphery of nest)

Plate 5.4 Freshwater catfish nest (a small cleared depression lacking pebbles and stones)

A number of nests were sampled for eggs and larvae during the breeding season. Multiple spawnings can apparently occur at the same nest. Sampling of one nest indicated three sizes of larvae (22 mm, 15 mm and 11 mm) ranging from at least 21 days to about 7 days of age. Other nests contained eggs and recently hatched fry. Different ages of eggs and larvae on the nest may be because a male may attract a number of females to the nest over time. This would likely be worthwhile for the male since it expends energy protecting the nest during this period. There was some evidence that several males may use the same nest over a breeding season and some nests had multiple spawnings during the breeding season. A freshwater catfish was observed on a nest, several weeks later a different fish (identified by a radiotransmitter) was observed on the nest, then several weeks later a fish without a Freshwater Ecology, NRE & Murray Darling Basin Commission

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transmitter was observed on this same nest. Many nests were within meters of each other and it was initially not clear whether the same fish made several adjoining nests. During the peak of the breeding period, five nests all within meters of each other all had different fish guarding them. However, it is still unknown if one fish may make several nests. Strong nest fidelity was observed on a number of occasions, particularly when eggs were in the nest. Fish were often seen circling the nest, picking between stones in the centre of the nest, presumably cleaning off silt. Redfin were frequently seen within the nest area sometimes picking between gravel, and the guarding catfish were observed to chase them away. 5.5.3 Fecundity and spawning Spawning has been recorded at dawn, mid morning and early afternoon (Lake 1967a, Merrick and Midgley 1981). The female lays eggs within the nest, which pass down through the gravel (Lake 1967a); whether eggs are fertilised by the male as they descend into the nest or once in the nest requires clarification. The milt appears clear (T. Raadik, DNRE, pers. obs.). Davis (1977b) observed that 5 out of 28 mature females failed to spawn by the end of the breeding season. Fecundity can vary for fish weighing between 1.25 kg and 2 kg, freshwater catfish from the Gwydir River produced between 9 000 and 15 000 eggs (Davis 1977b), compared to Lake’s (1967a) estimates at Narrandera of 18 000 to 26 000 eggs. Lake (1959) indicated that a 1.4 kg fish will produce about 20 000 eggs. The number of eggs may increase with fish size (Pollard et al. 1996). Eggs are spherical, demersal, non-adhesive, light green to yellow and are about 3.2 mm in diameter when water hardened (Lake 1967c). Davis (1977b) noted egg size increased with increased body weight and length of adults. 5.5.4 Larval growth While Lake (1967b) noted that eggs hatch in about 7 days at temperatures between 19 and 25oC; further work is required to determine if this temperature range is broader. For example, at a lake in Maryborough, Victoria, eggs were recorded at 28.6oC, although it is not known whether they hatched successfully. Larvae are about 7 mm in length at the time of hatching and lack barbels and pectoral fins. Seven days after hatching, the larvae measure 12 mm in length and have distinguishable barbels. They are free swimming by 12-14 days and feed by 20 days (Lake 1967b). Larvae measuring 13 mm, and approximately 2 weeks of age or less, were caught in a double winged glass eel net within metres of a nest, in 0.5 m of water at a lake in Maryborough, Victoria (Clunie, pers. obs.). Young can grow rapidly, measuring 15 to 19 mm when 17-21 days, 90 mm in the first winter, 300-340 mm by 16 months, 170360 mm by 30 months, 250-480 mm by 42 months and 500 mm by the sixth year (Lake 1967c, Merrick and Schmida 1984, Pollard et al. 1996). Such overlapping estimates for ages has been supported by recent otolith aging of a small number of specimens from several lakes in Victoria and New South Wales. Fish measuring 131195 mm (n=4) were estimated to be about one year old, 255-380 mm (n=9) about two years old, 330-481 mm (n=4) about three years old, 490-505 mm (n=3) about four years old, 350-470 mm (n=5) about five years old and one fish of 510 mm was estimated to be about 11 years old (DNRE, unpublished data). 5.5.5 Reproductive strategies of other Plotosidae Little research has been undertaken on the reproductive strategies of Plotosidae in Australia, with the majority of information known for Tandanus tandanus. There have Freshwater Ecology, NRE & Murray Darling Basin Commission

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been suggestions that other Plotosidae may build nests like Tandanus. However, Orr and Milward (1984) observed Neosilurus ater and N. hyrtlii to be flood spawners, moving upstream to spawn during monsoonal flooding. Neosilurus ater were observed to spawn in shallow riffles between flood peaks, with non-adhesive, demersal, eggs lodging amongst the gravel substrate. Orr and Milward (1984) suggest this breeding strategy suits the highly seasonal and unpredictable aquatic environment with rains providing the best conditions for growth and survival of young fish. Food availability may be highest during the wet season and oxygen may be unlimited. Upstream migration may also reduce pressure on young from predators. Orr and Milward (1984) noted the different breeding strategies of these members of the Plotosidae raises questions of the phylogenetic relationships within the family. The breeding strategy of other Australian species of Plotosidae does not appear to have been described. Table 5.1 Existing biological information for freshwater catfish Tandanus tandanus Inducement to spawn Spawning temperature Spawning period Age and weight at sexual maturity Max. known age Fecundity Spawning site

Spawning behaviour

Parental care Egg description Diameter of eggs Min. time to hatching Length of larvae at hatching Age at free swimming Age and length at end of larval development Habitat preferences adults

Habitat preferences juveniles

Behaviour Diet - adults

Diet - juvenile

Rise in water temperature1. Temperature of 24oC1, 2. Could be lower (eggs recorded on nest at 21oC) 16 October to January3, January to end of March2. Between 3 and 5 years, at a weight of 1.2kg4. At least 8 years4. One fish recently aged at 12 years (otoliths) (Raadik, DNRE, pers. comm. 1998). 9 000-15 000 eggs4, 18 000-26 000 eggs1 (1.25-2kg fish). Nest, built 1-2 weeks before spawning. Built by male5 . Circular to oval nests, of coarse sand or gravel with central sandy depression6. Can use stones and hard earth1 Nests may not consist of stones etc, and may be a small depression16 . ‘U’ shaped nests in Bellinger River7. Male forces female into nest. Courtship behaviour with weaving and circling8. The same nest can be used by several fish during the breeding season16 . Multiple spawnings can occur as indicated by different sizes of larvae, and eggs16 Nest usually tended by male, can be both in ponds8. Fan and protect eggs1. Spherical, demersal, non adhesive9. 3.1-3.4 mm when water hardened9. 151-167 hours9. 7.0-7.4 mm9. 12-14 days9. 24 days9, 14-16 mm9. Wide range of habitats. More abundant in lakes and backwaters10, although does occur and spawn in flowing streams3. In Qld rivers, most often found in areas with zero to moderate water velocity11. More common in deeper pools11. More common in undercut banks, root masses and large woody debris11. Preference for deep, slow flowing water, with bedrock substrate12(NSW). In Qld rivers, juveniles and subadults more common in runs11. Often in close association with aquatic macrophytes, filamentous algae and leaf litter11. More common with increasing gravel-mud substrates with aquatic plant cover and deposits of organic detritus12 (NSW). Adults usually solitary when not breeding, juveniles can form loose schools13. Opportunistic carnivore. Predominantly aquatic insects, followed by macrocrustacea, molluscs, detritus, with smaller amounts of terrestrial invertebrates and vegetation, fish, aquatic vegetation/algae and planktonic invertebrates11(Qld, NSW). Eat small prey (microcrustaceans, aquatic insect larvae)11. Size of prey increases with


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Freshwater Catfish – A Resource Document fish size14. Movement - life stage Adults apparently non-migratory4, 12, 15. Movement of juveniles unknown, possibly quite mobile (Moffatt, DNR, pers. comm. 1998) 1 2 3 Lake 1967a, Davis 1975, Merrick and Schmida 1984, 4Davis 1977a, 5Roughley 1951, 6Pollard et al. 1996, 7Musyl and Keenan 1996, 8Merrick and Midgely 1981, 9Lake 1967d, 10Lake 1967c, 11Kennard and Pusey 1997, 12Richardson 1984, 13Cadwallader and Backhouse 1983, 14Davis 1977b, 15Davis 1977c, 16Clunie, unpubl. data


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6 Case Studies Several case studies are provided below, including sites where freshwater catfish has declined dramatically, as well as where abundant populations are known to still occur. Such sites provide valuable insights into possible reasons for the species' decline as well as habitat features which may be important. Plate 6.6 at the end of this section indicates where these sites are located within the Murray Darling Basin. 6.1 Barren Box Swamp, New South Wales a) Decline of a healthy freshwater catfish population Barren Box Swamp, approximately 3 000 ha in size, lies about 25 km north west of Griffith in New South Wales and receives inflows from Mirrool Creek. The swamp has experienced significant changes since irrigation commenced from about the 1930s. The swamp was once characterised by a diverse aquatic fauna and flora and was popular with duck hunters. While once supporting a healthy population of freshwater catfish, the swamp is now highly degraded and has been referred to as an 'aquatic desert' (Moorfield 1995). Although the specific reason why freshwater catfish declined significantly in Barren Box Swamp is not known, it is worthwhile reviewing the changes which have occurred in this area and the conditions during which the species flourished. Prior to irrigation drainage, the area was an intermittent wetland, probably characterised by swamp vegetation such as Lignum Muehlenbeckia florulenta and Cane Grass Eragrostis australasica with Black Box Eucalyptus largiflorens near the mouth of Mirrool Creek. From the 1930s to early 1950s the water regime remained intermittent but became wetter. In the 1950s the water levels increased as a result of a big infill and flood years, and the swamp became permanent. During this time, Black Box trees and lignum declined because of the persistent high water levels and Cumbungi invaded. The swamp was generally drier in the 1960s, showing a seasonal pattern in water level with a yearly water level range of about 1 m. While the swamp was dominated by Cumbungi there was also a diverse submerged flora including Ribbonweed, pondweeds, Hornwort Ceratophyllum demersum, Sea Tassel and Waternymph Najas spp. The water was clear at this time. In the late 1960s the storage capacity of the swamp was increased and the centre became too deep for Cumbungi (J. Roberts, CSIRO, pers. comm. 2000). In the 1970s the water level in the swamp increased due to flooding and the changes in water level were unpredictable. The decline of Cumbungi began: this was most likely primarily due to changes in water regime, although carp and herbicides may have played a minor role in causing changes. By the early 1980s the swamp had become an open turbid lake with only a narrow fringe of Cumbungi. The water regime was very erratic, and the unstable bottom and abundance of carp made germination and establishment of aquatic vegetation unlikely (J. Roberts, CSIRO, pers. comm. 2000). More recently, infestations of Alligator Weed Alternanthera philoxeroides have occurred and required a control and containment program. The swamp is now closed to duck hunting.


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Some water quality monitoring has occurred in Barren Box Swamp. Monitoring between 1978 and 1993 indicated that over 80% of the conductivity values are below those recommended for irrigation reuse of drainage water (Shepheard 1994). Turbidity has significantly increased in the swamp, with increases in 1982/83 and again in 1989 onwards. High turbidity levels are now considered characteristic of the swamp (Shepheard 1994). Over 90% of the measurements of total phosphorous levels were moderate. Pesticide residues have been recorded in recent monitoring of water samples including endosulphan sulphate. Barren Box Swamp once supported a healthy population of freshwater catfish. One commercial fishermen indicated that about 10 000 fish were taken from the swamp between 1980 and 1988. Others described how the swamp once "… teemed with catfish …" (Moorfield 1995). There is now no longer a significant population of freshwater catfish within the swamp.


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6.2 Wimmera River, Victoria b) Establishment of a healthy freshwater catfish population The Wimmera River is located in the semi arid west of Victoria. It is a closed river system and much of the area has an intermittent flow regime. While in the past the water supply was unreliable, the system has been exploited and regulated for almost 100 years with the creation of weirs and open earthen channels to divert water. The fish fauna of the Wimmera catchment is diverse: twenty one species have been recorded in the Wimmera River and tributaries of which only six occur naturally. Many species have been deliberately introduced for recreational angling. In the early 1970s, 600 freshwater catfish from the Murray River were stocked downstream of Dimboola by the Dimboola Angling Club. There have been subsequent translocations of fish within the river including Horsham and Antwerp (Anderson and Morison 1989). The species appears to have established healthy self-sustaining populations within parts of the Wimmera River. While freshwater catfish has declined markedly within most Murray Darling Basin rivers in Victoria, this introduced population has thrived. It is worthwhile comparing key features of the Wimmera River which may vary from other areas. The flow regime of the Wimmera River is different from many other rivers within Victoria, and may be a key reason why freshwater catfish have thrived. Anderson and Morison (1989) conducted a detailed study concerning environmental flow requirements in the Wimmera catchment. The variability of annual discharge in the Wimmera River is greater than for most other Victorian streams. The river becomes more intermittent with distance downstream, and the lower Wimmera River frequently ceases flowing in summer and becomes a series of pools. Anderson and Morison (1989) note that at Horsham, regulation has not changed flooding patterns and has had more of an effect on low to moderate discharge. Diversion weirs are small, most impoundments are offstream and are not operated for flood mitigation. Diversions now prolong periods of low flow and absorb small to moderate flow events. At Horsham, bankfull discharge events are irregular with a relatively long return period. Periods of low flow (600 mg/L and oxygen saturations of 130% and that the Wimmera River has been assessed as having one of the lowest suitabilities for aquatic fauna in Victoria. Ryan et al. (1999) suggest that at the current rate of increase, the conductivity at periods of low flow is likely to approach levels that only the most tolerant freshwater biota area able to tolerate. Freshwater catfish has been found to be tolerant of high salinities and depleted dissolved oxygen during trials within the Wimmera River (Ryan et al. 1999). Ryan et al. (1999) suggested that the species could possibly inhabit saline pools although may not feed given the relatively depauperate assemblage of aquatic biota and elevated levels of H2S and heavy metals contained in the substrate. There is prolific aquatic vegetation in areas including Cumbungi and reed growth; freshwater catfish are frequently caught from areas with abundant aquatic vegetation. Overman (1996) notes aquatic vegetation in the middle sections of the Wimmera are characteristic of a still, nutrient-laden system rather than a stream system. Algal blooms occur regularly. Plate 6.1 Wimmera River

6.3 Cardross Lakes, Victoria c) A healthy freshwater catfish population There is a system of 41 lakes within the mallee dunefields in northern Victoria. Of these nine form the Cardross lakes basin complex, a series of interconnected drainage lakes. The lakes are artificial wetlands which have been created and maintained by Freshwater Ecology, NRE & Murray Darling Basin Commission

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excess irrigation water and irrigation run-off. Five of the lakes have been studied intensively in recent years (see Raadik and Fairbrother 1999). The Cardross Lakes system has a very high diversity of native aquatic species and a low diversity of exotic species (Raadik and Fairbrother 1997). It is a particularly significant area since three fish species considered threatened in Victoria occur within the lakes: freshwater catfish, Murray hardyhead Craterocephalus stercusmuscarum fulvus and southern purple-spotted gudgeon Mogurnda adspera (NRE 1999). Both freshwater catfish and Murray hardyhead have large self-sustaining populations within the lakes. A further five native species and four introduced species have been recorded from the basins (Raadik and O'Connor 1996). Carp are relatively widespread and abundant in most lakes surveyed, while redfin appear to have a very restricted distribution and have not been recorded in the three basins surveyed most frequently. The Cardross Lakes system is a considered a significant site for freshwater catfish in Victoria. It is not known how the species reached this system although it is possible fish were stocked or entered with irrigation water from the Murray River. This species has consistently been ranked as the third most abundant large bodied fish species in surveys with bony bream and carp being more common (Raadik and Fairbrother 1999). Three basins in particular contain large self-sustaining populations of this species. These lakes have a predominantly silt substrate, contain small diameter woody debris and usually contain abundant aquatic vegetation including submerged vegetation (Sea Tassel) as well as dense fringing areas of Cumbungi. The amount of aquatic vegetation has varied in recent years with fluctuations in water levels. Maximum water depths recorded in recent surveys have ranged between 1 and 5.75 m. While they range in profile, about 40-60% of the lakes are relatively shallow (