Point Labatt Marine Reserve

Final report to the Department for Environment and Heritage

Point Labatt Marine Reserve: Evaluating the effects of reserve closure on the biota of subtidal reefs

David R. Currie and Shirley J. Sorokin October 2005

SARDI Aquatic Sciences Publication No. RD04/0123-2 SARDI Research Report Series No. 103

Pt Labatt Marine Reserve Assessment

Title:

Point Labatt Marine Reserve: Evaluating the effects of reserve closure on the biota of subtidal reefs

Sub-title:

Report to the Department for Environment and Heritage

Authors:

D.R. Currie and S.J. Sorokin

South Australian Research and Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach SA 5024 Telephone: (08) 8207 5400 Facsimile: (08) 8207 5406 http://www.sardi.sa.gov.au

The authors do not warrant that the information in this report is free from errors or omissions. The authors do not accept any form of liability, be it contractual, tortious or otherwise, for the contents of this report or for any consequences arising from its use or any reliance placed upon it. The information, opinions and advice contained in this report may not relate to, or be relevant to, a reader’s particular circumstances. Opinions expressed by the authors are the individual opinions of those persons and are not necessarily those of the publisher or research provider.

© 2005 SARDI Aquatic Sciences This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the authors.

SARDI Aquatic Sciences Publication No. RD04/0123-2 SARDI Research Report Series N. 103 ISBN 0 7308 5336 5 Printed in Adelaide October 2005. Author: Reviewers: Approved by:

D.R. Currie and S.J. Sorokin Dr. Stephen Mayfield & Dr. Jason Tanner Dr. John Carragher

Signed: Date: Distribution: Circulation:

25th October 2005 Department for Environment and Heritage, PIRSA Fisheries, SARDI Aquatic Sciences Library Public Domain

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TABLE OF CONTENTS LIST OF FIGURES .............................................................................................................................. II LIST OF TABLES ...............................................................................................................................III LIST OF APPENDICES......................................................................................................................IV 1

EXECUTIVE SUMMARY ......................................................................................................... V

2

INTRODUCTION ........................................................................................................................ 1 2.1 2.2

3

BACKGROUND INFORMATION................................................................................................. 1 RATIONAL AND OBJECTIVES................................................................................................... 2

METHODS.................................................................................................................................... 2 3.1 DIVE SURVEY ......................................................................................................................... 2 3.1.1 Substrate type ................................................................................................................... 3 3.1.2 Macro-algae...................................................................................................................... 3 3.1.3 Motile invertebrates.......................................................................................................... 3 3.1.4 Demersal fish.................................................................................................................... 3 3.2 BATHYMETRY ........................................................................................................................ 3 3.3 DATA ANALYSIS..................................................................................................................... 4

4

RESULTS...................................................................................................................................... 4 4.1 4.2 4.3 4.3.1 4.3.2 4.4 4.4.1 4.4.2 4.5 4.5.1 4.5.2 4.6 4.6.1 4.6.2 4.7

5

BATHYMETRY ........................................................................................................................ 4 GEOMORPHOLOGY ................................................................................................................. 5 DIVER TRANSECTS - GENERAL OBSERVATIONS ...................................................................... 5 Substrate type ................................................................................................................... 5 Canopy cover.................................................................................................................... 7 MACRO-ALGAE ...................................................................................................................... 9 Species richness and abundance....................................................................................... 9 Community structure...................................................................................................... 10 MOTILE INVERTEBRATES ..................................................................................................... 12 Species richness and abundance..................................................................................... 12 Community structure...................................................................................................... 15 DEMERSAL FISH ................................................................................................................... 17 Species richness and abundance..................................................................................... 17 Community structure...................................................................................................... 20 TROPHIC RELATIONSHIPS BETWEEN BENTHOS AND FISH ...................................................... 22

DISCUSSION.............................................................................................................................. 23 5.1 5.2 5.3 5.4

SPATIAL VARIABILITY IN BENTHOS AND FISH ....................................................................... 23 BIODIVERSITY AND ENDEMISM ............................................................................................ 24 COMMERCIALLY IMPORTANT SPECIES .................................................................................. 24 SURVEY DESIGN ................................................................................................................... 25

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CONCLUSIONS......................................................................................................................... 26

7

REFERENCES ........................................................................................................................... 26

8

ACKNOWLEDGEMENTS ....................................................................................................... 28

LIST OF FIGURES Figure 1. Map of the western Eyre Peninsula showing the location of the Point Labatt Marine Reserve. ................1 Figure 2. Schematic representation of the depth-stratified survey design. Solid black circles denote the nominal locations for 16 * 50m diver transects. Solid green circles designate the reserve boundary positions and are accompanied with geographic coordinates in WGS 84 datum.........................................................................2 Figure 3. Three-dimensional map of the seabed topography at the Point Labatt Marine Reserve (hatched area). Depth (m) is provided in the vertical axis, while base axes detail latitude and longitude (WGS84 Datum). Locations of diver transects are denoted by red-filled circles..........................................................................4

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Figure 4. Hydrographical map of the study area showing the locations of 16 * 50m diver transects (connected redfilled circles) inside and outside the Point Labatt Marine Reserve (wireframe connecting green-filled circles). Note that the first 2 characters in each station label denote region (NO=North Outside, SO= South Outside, NI= North Inside, SI= South Inside), while the trailing numerals indicate depth in metres (5, 10, 15, 20)....................................................................................................................................................................5 Figure 5. Map of Point Labatt Marine Reserve (wireframe) showing the relative proportions of key substrate types (rock, cobble, sand) at 16 diver transects.........................................................................................................6 Figure 6. Map of Point Labatt Marine Reserve (wireframe) showing relative proportions of benthic canopy cover (bare, brown algae, green algae, red algae) at 16 diver transects. ....................................................................7 Figure 7. Bubble plot showing the total number of algal species collected from 2*1m2 replicate diver scrapings at 16 transects off Point Labatt. Numbers in each bubble represent total species number...................................9 Figure 8. Bubble plot showing the total algal biomass collected from 2*1m2 replicate diver scrapings at 16 transects off Point Labatt. Numerals in each bubble represent total wet weight in kilograms. ......................10 Figure 9. Non-metric MDS plot of algal community structure at 16 transects off Point Labatt. Depth strata are represented in the ordination by different colours (yellow = 0-5m, blue = 5-10m, green = 10-15m, red = 1520m), and sampling regions by different shapes (squares = inside the reserve, circles = outside the reserve). .......................................................................................................................................................................11 Figure 10. Bubble plot showing the total number of motile invertebrate species found at 16 transects (100m2) off Point Labatt. Numerals in each bubble represent total species number. ........................................................13 Figure 11. Bubble plot showing the total abundance of motile invertebrates found at 16 transects (100m2) off Point Labatt. Numerals in each bubble represent total number of individuals. .......................................................13 Figure 12. Bar graphs showing the mean abundance (N/100m2 ± se) of the three most common invertebrate species: a) Turbo undulatus, b) Haliotis rubra, and c) Comanthus trichoptera found at four depth strata inside (green bars) and outside (blue bars) the Point Labatt Marine Reserve. ...............................................14 Figure 13. Non-metric MDS plot of invertebrate community structure at 16 transects off Point Labatt. Depth strata are represented in the ordination by different colours (yellow = 0-5m, blue = 5-10m, green = 10-15m, red = 15-20m), and sampling regions by different shapes (squares = inside the reserve, circles = outside the reserve). .........................................................................................................................................................16 Figure 14. Bubble plot showing the total number of demersal fish species found at 16 transects (500m2) off Point Labatt. Numerals in each bubble represent total species number...................................................................18 Figure 15. Bubble plot showing the total abundance of demersal fish observed at 16 transects (500m2) off Point Labatt. Numerals in each bubble represent total number of individuals. .......................................................19 Figure 16. Bar graphs showing the mean abundance (N/500m2 ± se) of three common fish species: a) sweep Scorpis aequipinnis, b) blue-throated wrasse Notalabrus tetricus, and c) blue groper Achoerodus gouldii. found at four depth strata inside (green filled bars) and outside (blue filled bars) the Point Labatt Marine Reserve. .........................................................................................................................................................20 Figure 17. Non-metric MDS plot of demersal fish community structure at 16 transects off Point Labatt. Depth strata are represented in the ordination by different colours (yellow = 0-5m, blue = 5-10m, green = 10-15m, red = 15-20m), and sampling regions by different shapes (squares = inside the reserve, circles = outside the reserve). .........................................................................................................................................................21

LIST OF TABLES Table 1. Mean substrate type (% ± s.d.) occurring at four depth strata inside and outside the Point Labatt Marine Reserve. Estimates are based on observations of 12*1m2 quadrats located along each of 16*50m diver transects. ..........................................................................................................................................................6 Table 2. Results of two-way ANOVA’s on differences in substrate cover (%) at four strata (depth) inside and outside the Point Labatt Marine Reserve (region). ..........................................................................................7 Table 3. Mean canopy cover (% ± s.d.) occurring in four depth strata inside and outside the Point Labatt Marine Reserve. Estimates are based on observations of 12*1m2 quadrats located along 16*50m diver transects. ...8 Table 4. Results of two-way ANOVA’s on differences in benthic canopy cover (%) in four strata (depth) inside and outside the Point Labatt Marine Reserve (region).....................................................................................8 Table 5. Results of two-way ANOVA’s on differences in algal richness (mean number of species) and algal biomass (mean wet-weight) in four strata (depth) inside and outside the Point Labatt Marine Reserve (region). Note that the mean area of reef in each transect is included as a covariate (rock) in the ANOVA model. ............................................................................................................................................................10

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Table 6. Results of analysis of similarity (ANOSIM) test for differences in algal community structure between 4 depth strata (0-5m, 5-10m, 10-15m, 15-20m) at Point Labatt........................................................................11 Table 7. Mean biomass (wet weight: g per 2m2) of algal species in 4 depth strata at Point Labatt. Species listed were identified from SIMPER analysis as contributing ≥ 5% to the similarity within and dissimilarity between regional groupings. Species indicative of each strata (contributing ≥ 10% to the total similarity within a strata) are highlighted in bold. .........................................................................................................12 Table 8. Results of two-way ANOVA’s on differences in invertebrate richness (mean number of species) and abundance (mean N) at four strata (depth) inside and outside the Point Labatt Marine Reserve (region). Note that the mean area of reef in each transect is included as a covariate (rock) in the ANOVA model..............13 Table 9. Results of two-way ANOVA’s on differences in invertebrate abundance (mean N) at four strata (depth) inside and outside the Point Labatt Marine Reserve (region). Note that the mean area of reef in each transect is included as a covariate (rock) in the ANOVA model.................................................................................15 Table 10. Results of analysis of similarity (ANOSIM) test for differences in invertebrate community structure between 4 depth strata (0-5m, 5-10m, 10-15m, 15-20m) at Point Labatt. .....................................................16 Table 11. Mean abundance (N per 100m2) of motile invertebrate species in 4 depth strata at Point Labatt. Species listed were identified from SIMPER analysis as contributing ≥ 5% to the similarity within and dissimilarity between regional groupings. Species indicative of each strata (contributing ≥ 10% to the total similarity within a strata) are highlighted in bold. .........................................................................................................17 Table 12. Results of two-way ANOVA’s on differences in fish richness (mean number of species) and abundance (mean N) at four strata (depth) inside and outside the Point Labatt Marine Reserve (region). Note that the mean area of reef in each transect is included as a covariate (rock) in the ANOVA model...........................18 Table 13. Results of two-way ANOVA’s on differences in fish abundance (mean N) at four strata (depth) inside and outside the Point Labatt Marine Reserve (region). Note that the mean area of reef in each transect is included as a covariate (rock) in the ANOVA model. ...................................................................................19 Table 14. Results of analysis of similarity (ANOSIM) test for differences in fish community structure between 4 depth strata (0-5m, 5-10m, 10-15m, 15-20m) at Point Labatt........................................................................21 Table 15. Mean abundance (N per 500m2) of demersal fish within two depth groupings (5-10m depth strata & all other depth strata combined (0-5m + 10-15m + 15-20m)) at Point Labatt. Average dissimilarities and associated standard deviations (SD) for all pairwise coefficients are presented in this table, together with their percentage and cumulative contributions to the total dissimilarity between the two groupings (66.05). .......................................................................................................................................................................22 Table 16. Mantel correlation coefficients (ρ) for pairwise comparisons of algae, invertebrate and fish community structure at Point Labatt. Contrasts are based on root-transformed Bray-Curtis dissimilarities matrices that include 16 transect locations. Significance values for these correlations are provided in brackets...............22

LIST OF APPENDICES Appendix 1. Locations of the start and end points of 16 transect sampled for substrate, algae invertebrates and fish between 25 November 2004 and 30 March 2005. Note that WGS 84 datum was employed for all position fixes. ..............................................................................................................................................................29 Appendix 2. Distribution and biomass (wet-weight in g) of 73 algal species collected in diver scrapings (2 x 1m2 quadrats x 16 transects) off Point Labatt. ......................................................................................................30 Appendix 3. Distribution and abundance of 29 motile invertebrate species collected at 16 transects (100m2) off Point Labatt. ..................................................................................................................................................31 Appendix 4. Distribution and abundance of 17 demersal fish species observed at 16 transects (500m2) off Point Labatt.............................................................................................................................................................31 Appendix 5. Photographic plates depicting 73 species of algae collected off Point Labatt during the 2004/05 dive survey. ...........................................................................................................................................................32 Appendix 6. Photographic plates depicting 29 motile invertebrate species collected off Point Labatt during the 2004/05 dive survey.......................................................................................................................................37 Appendix 7. Photographic plates depicting 17 species of demersal fish observed off Point Labatt during the 2004/05 dive survey.......................................................................................................................................39

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1

EXECUTIVE SUMMARY

1.

The Point Labatt Marine Reserve, situated on the western Eyre Peninsula, was established to conserve one of the largest mainland breeding colonies of Australian sea lions (Neophoca cinerea) in Australia. Since its declaration in 1988, public access to the reserve has been prohibited, as has fishing and the removal of any marine organism. This report presents results and principal findings from a field research program aimed at quantifying marine community differences between the Point Labatt Marine Reserve and adjacent unprotected reference sites.

2.

Bathymetric data were acquired to characterise sub-tidal bedforms in the study area and inform the survey design. These data showed that 44% of the seafloor within the reserve was comprised of shallow-reef habitat (