Biomass and Production of Fishes in Natural and ...

Biomass and Production of Fishes in Natura ized Streams Cameron B. Portt, Eugene K. Balon,' and David L. G. Noakes Can. J. Fish. Aquat. Sci. Downloaded from www.nrcresearchpress.com by Oregon State University on 05/16/14 For personal use only.

Department of Zoology, Croup for Advancement of Fish Studies (CAFS), University of Cuelph, Cuelph, Ont. N 7 6 2 W I

Portt, C. B., E. K. Balon, and D. L. G. Noakes. 1986. Biomass and production of fishes in natural and channelized streams. Can. ). Fish. Aquat. Sci. 43: 1926-1934. Fish biomass and production were estimated at two channelized and two unchannelized stream sections. Biomass and total and available production were much lower in the channelized sections than in the natural sections. Regressions of the log of production versus the log of initial biomass had slops significantly different from 1. This i s apparently due to changes in age structure which occurred concurrently with changes in biomass. The physical homogeneity of channelized streams provides opportunities for manipulative research. Nous awns calcul6 la biomasse et la production de poisson dans deux portions de cours d'eau eanaliskes et deux portio~tsnon canaliskes. La biomasse, la production totale et la production disponible etaient beaucoup plus basses dans les portions canalis6es que dans Ies autres. bes rkgressions pratiquees sur le Iogarithme de la production par opposition au logarithme de la biomasse initiale donnaient des courbes nettement diffkrentes de 1. Ce ph6nomGne est apparemment dO A des modifications dans la structure des Ages qui se sont produites en meme temps que des changements de Ia biomasse. L'hornog6n6it6 physique des cows d'eau canalis$s permet de proceder 2 des manipulations.

Received january 4 , 984 Accepted dune 24, 1986 (97651 )

treams in southern Ontario are often modified to benefit agriculture. One common modification is straightening of the stream channel and removal of any obstructions to flow, a practice commonly referred to as channelization. The i lnpact of stream channelization on fish communities is assumed to be negative (Griswold et aH. 1982) but few studies have quantitatively examined the effect of channelization on stream fish conarnunities, and those which have (Congdoaa 1971; Bayless and Smith 1967) have only determined the effect on fish biomass, In this study we compare fish production and biomass and their interrelationships in channelized and unchanwelized stream segments. Other researchers have estimated fish production in streams which varied in physical characteristics (Lotrich 1973; O'Connsr and Power 1976; Small 1975). Their hypothesis was that the rate of fish production would be different in physically different habitats, and indeed this proved to be the case. However, it is also important to know if fish production is similar in physically similar habitats (Mahon and Balon 1985; Watson and Balon 9984). The physical similarity between the two channelized sites also allowed us to test this frequently unstated assumption.

Materials and Methds Study Area Mud Creek and North Branch Creek both arise in Oxford County, Ontario, and have average gradients of 0.1 and 0.2%? Author to whom aII ccsnespondence should be addressed. 1926

respectively (Department of Energy, Mines and Resources 1972). They join (43"08'N9 80°54'W) to form the Middle Thames River which ultimately drains into Lake St. Clair. The underlying bedrock of Silurian and Devonian sediments is overlain by glacial drift of varying texture and thickness (Wickland and Richards 1961). Land use within the watershed is gredominantly agricultural. The lower 8 krn of Mud Creek was channelized in 1971, 6 yr prior to the beginning of this study, time sufficient for recolonization and stabilization of the fish community (Griswold et al. 1982). Fish biomass and production were estimated at two locations within the channelized pastion of Mud Creek (MC2, MC3) and at two locations which had not been channelized on Mud (MC 1) and North Branch creeks (NBC, Fig. I). The sampling sites were bordered by abandoned fields and pastures except at MC2 where a partially wooded buffer strip occurred between the north bank of the creek and a hay field. The substrate at MC1 was predominantly silt with small amounts of sand and occasional boulders. There were no riffles and only one distinct pool within the section. Sites MC2 and MC3, which were within the channelized portion of Mud Creek, exhibited little within-site variation in depth and had sand substrate. The upstream portion of site NBC was a riffle with gravel and rubble substrate whereas the lower portion was a sun with sand substrate. At each site, bransects were taken at 2-m intervals along a base line which was parallel to the stream. The distances to both banks and to each 18-crn depth increment were measured and the maximum depth was determined along each transect. These coordinates were plotted and a bathymetric map sf each site was prepared from which the area, volume, and mean depth sf each site was determined (Table I). Can. J . Fish. Aqua!. Sci., VoE. 43, 1986

TABLEI . Physical characteristics of the four sites. S ite

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Date

MC B June 7 , I974

Length (m)

112

Mean width (m) Area (m2) Mean depth (cm) Maximum depth (cm) Mean sufiace velocity (rn-s-')

3.3 368 35 64 0.12

PIG. 1. Study area.

Collection of Fishes At each Eocation the designated section of stream was blocked off using 3-mm circular-mesh netting. Each site was fished seven to nine times using a Smith-Root type VZ electrofisher which delivered pulsed BC current at 60 pps and 560 V. The duration of each fishing and of rest periods between fishings was kept constant at each site. Following capture, all fish were preserved in 10% fomalin. They were identified several weeks later using keys in Scott and Crossman (1973) and Trautman (1957). For each species the standard length (SE) of all individuals was determined to the nearest millirnetre and their total weight was determined to the nearest gram. Density Estimates and Determination of Age, Growth, and Sex Because effort was kept constant between fishings at each Eocation, the simplification of Leslie's method of relating catch and cumulative catch (Leslie and Davis 1939; Ricker 1975) was used to estimate fish abundance. The abundance of species which exhibited a wide size range was estimated separately for different length classes (DeEury 1947; Sullivan 1956; Stewart 1975). Subsamples of 5 (MC2, MC3) or 10 (MC 1, NBC) individuCan. J. Fish. A q ~ a t Scb., . Vol. 43, 1986

Me2

MC3

NBC

June 5. 1977 92 4.9

July 5, 1974

July 8, 1977 58

454 I5 34 0.24

70 7.2 505 II 40 0.22

6.5 376 I3 40 0.36

als were taken from each millimetre length group of the species for which production was calculated, where possible. If fewer individuals were present, all individuals in that length group were processed. Each fish so selected was rinsed in water and blotted dry. Fish weighing less than % g were weighed to the nearest 0.01 g; fish weighing more than 1 g were weighed to the nearest 0.1 g. Four key scales (Segerstrile 1933) were remc~vedfrom each individual in the subsample and mounted dry between glass slides. The body cavity was then opened and gonads which could not be sexed by eye were examined microscopically. Fish which could not be sexed in this fashion were considered juveniles. The proportion of mature females in each size group was determined. Scales were examined and an age was assigned based on the number of annuli observed. Some older fish had not yet formed an annulus in the year of collection. If the distance between the last annulus and the scale margin was large relative to the distance between the last two annuli, an age 1 yr greater than the number of annuli was assigned (Balon 1972, 1974). The distance from the focus to the scale margin and to each annulus was measured. If an individual had not yet formed an annulus in the current year the scale margin was considered to be the current year's annulus. Aging was validated by the examination of length-frequency distributions for all species. Total and available production were calculated from the time of spawning using the algebraic method (Ricker 1946; Balon 1974) as outlined in Mahon and Balon (8977). At sites MCI and MC2 the time of collection coincided with the time sf spawning for all species except Catssrorn~scsmmersomi. Therefore, the estimated abundance and the mean weight of each age group at the time of collection were used in the production calculations. For sites MC3 and NBC and for C. cornmersoni at MCl, spawning preceded collection by approximately 1 mo. The number of fish in any age group at the time of spawning (Nil was estimated by adjusting the number in that age group at the time of collection (Ni+) using the formula Ni = N , + 8',where Z is the instantaneous rate of change in numbers and t is the fraction of a year between the time of collection and of spawning, in this case 1/22. Examination of scales from fishes collected at MC1 and MC2 indicated that the younger age classes had grown considerably during the current year (since annulus formation) although many of the older individuals had not yet formed the current year's annulus. Therefore, a correction factor was calculated for each age class by expressing the difference between the mean scale radius and the mean distance to the current year's annulus as a percentage of the former (see Portt and BaHon 1984). These correction factors were used to estimate the scale radius at the time of spawning for species at M e 3

TABLE2. Estimated number

( k )and biomass (i)present a the rime of collection and percentages of total in parentheses.

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MC 1

MC2

MC3

NBC

Nofropis cornubus Sernoti&uscatromacula6Pteas Rhy~aickathysa mPU!US %8'scornksspp. Et&eos&omnigrusza E . microperca Pimephsles notatus Cu6aea i~constans Notropis rubBe&1us Ethesstoma cglersadeum E. Jabe6iare Pimephales prornekzs Umbra limi Hypentebium nigricans C a t o s ~ ~ m c~~mmersogli e~s Lepomis gibbosus Etheostorna kP&ennuides Ambloplites rupestrbs Norropis hudsonices N . vo&uee88us Noturus Javus

Totrpls T ~ t a l sm-2

Mean weight of an individual (g)

and NBC. The mean of the comectisn factors calculated for cyprinids at MCI and M e 2 was used for Notropis rubelbus and Nocornis spp. The mean conection factors for age I Etheostoma nigrurn were used for age I f Etheostoma biennkoides, E. caerulelam, and E . flabellare. For each age a weighted mean length was calculated from the mean back-calculated lengths at that age for all age classes present and the estimated number of fish in each age class. Mean weights were estimated by substituting weighted mean standard lengths into the appropriate weight versus standard length equations (Mahon and Balsn 2977; Mahon et al. 1979; Halyk and Balon 1983). This method can result in mean weights being underestimated (Nielson and Schoch 1980); however, the mean enor in this study was small (