126 Size, Age and Growth ofnesting Male Pumpkinseed Sunfish (Lepomis gibbosus) in Rat Cove, Otsego Lake, NY John R. O'Connor l, John R. Foster, John Urban 3, and Jim Hakala 4 ABSTRACT Male pumpkinseed sunfish nesting in Rat Cove, Otsego Lake were angled from their nests, scales taken, aged, and back calculation of growth was determined for each fish. Nesting males were found to have a mean size of l18mm and a mean age of 4+ years. Age and growth ofnesting males was similar to research from other cold water bodies. NTRODUCTON Pumpkinseed prefer shallow, weedy expanses of warm water (Trautman, 1981). Otsego Lake is a deep, cold, steep-sided, mesotrophic lake. ts limited littoral zone is not well suited for pumpkinseed nesting. Suitable nesting habitat is limited and shared with many other warm water fish such as bluegills (Lepomis macrochirus), red-breasted sunfish (Lepomis auritus), largemouth bass (Micropterus salmoides), and carp (Cyprinus carpio) (MacWatters, 1983). Furthermore, good pumpkinseed nesting habitat is continuously disturbed by spawning carp. The goal of this study was to determine ifthe population dynamics of nesting male pumpkinseed in a cold water lake with limited nesting sites were similar to that described for warm water lakes with extensive nesting sites. n order to meet this goal, size, age of sexual maturity and the growth ofnesting males were studied in Rat Cove. This paper is part ofa larger study examining the nest site selection and spawning success of pumpkinseed in Otsego Lake. MATERALS AND METHODS Otsego Lake is located in Otsego County, New York at the headwaters ofthe Susquehanna watershed. The lake is 168 feet deep, 8.25 miles long and an average of 0.8 miles wide. This study took place in Rat Cove located along the southwest shore about one mile north of Cooperstown (Fig. 1). The study site was chosen because it supported the highest pumpkinseed density in the lake (Foster 1996). 1996 1,1995 3, 1994 4 Robert C. MacWatters nternship in Fisheries and Aquatic Science. 2BFS Visiting Researcher, 1994-96. Fisheries and Aquaculture, SUNY College of Agriculture and Technology, Cobleskill, New York 12043
127 CRPf'LE CREU BLACKBRD 8AY WLLOW BROO( SUSOUEHANNA AVER Figure 1: Bathymetric map of Otsego Lake and a close-up of Rat Cove (depth in feet).
128 Data were collected from mid June through early August, 1994-1996 (mean water temperature 22 c). Small numbered rocks were to denote individual nests and fish. Nesting male pumpkinseeds were angled from their nests and anesthetized with 2 phenoxyethanol. Total length was measured and scales removed from behind the operculum. Fish were immediately returned to their nests. Scales were removed from behind the operculum, just above the pectoral fm and read on a micro-fiche reader (42X magnification). Age and back-calculation of growth was determined tor each fish following the guidelines ofregier (1962), Lux (1971), Casselman (1987), and Jearld (1992). RESULTS 1994 1995 1996 41 45 48 Age range (in years) 3+ to 8+ 3+ to 6+ 2+ to 9+ Mean age (in years) 4+ 4+ 4+ Size range (in mm) 107-151 98-152 97-149 Mean size (in mm) 126 119 118 The mean age of nesting male pumpkinseed in Rat Cove has remained 4+ years for the duration ofthe study (Figure 3). The mean length has decreased by eight millimeters over the past three years, while the size range has remained relatively stable (Figure2). DSCUSSON Pumpkinseed usually reach maturity by age two (Scott and Crossman. 1973). n 1994 and 1995 the youngest nesting male was 3+, however in 1996, two ofthe nesting males were 2+ years. Both were large fish for their age but neither spawned successfully. These data suggest that the majority of male pumpkinseed sunfish don't reach sexual maturity until age 3+ in Rat Cove (Figure 4). Ten years ago, Otsego Lake pumpkinseed grew faster and larger than they do today (Austin et al.. 1986). This change in size and growth may be an indication of overpopulation and stunting, or may be due to a loss of valuable littoral zone habitat. Danylchuk and Fox (1994) described the age and growth of pumpkinseeds in Little Round Lake, a deep meromictic lake with limited littoral zone. Pumpkinseed there show very slow growth and only obtain a length around 100mm. Slow growth in the cold waters of Otsego Lake seems to result in a similar delay in maturity. Most other pumpkinseed studies have been conducted in warm, mesotrophic and eutrophic water
129 25 C1l 20 n:l ~ en Z- s:: 15 :i:j C1l 10 0... C1l.0 E 5 ::J Z 0 95-99 105-109 115-119 125-129 135-139 145-150 Total Length (mm) of Fish Figure 2: Length-frequency distribution of nesting male pumpkinseed sunfish (N=134) in Rat Cove, Otsego Lake, 1994-1996. 45 40 35.J:::. 30 -LL 25 0... C1l 20.0 E ::J z 15 10 5 0 2+ 3+ 4+ 5+ 6+ 7+ 8+ 9+ Age (in years) Figure 3: Age-frequency distribution of nesting male pumpkinseed sunfish (N=134) in Rat Cove. Otsego Lake. 1994-1996.
~ 130 Rat Cove Growth Curve 160 140 120 - E E 100 c :::...r:... C) 80 c Q)...J C ~ Q) ::!: 60 40 20 o 1+ 2+ 3+ 4+ 5+ 6+ Age of Nesting Males 1 -------------~----T----f------- j. i J _ - - - - 1- ~ 1- -J - - - - - - - - _ - - - T - - - - - - - - - i- -.- - -1- - - - j ---'----T----r----r--------, r --------~---------~---- ----1---- j!..j.1 L 1, - - - - '- - - - - - - - - -t - - - - j - - - - ~ - - - -,- - - - -, - - - - 7+ 8+ 9+ Figure 4: Growth curve of nesting male pumpkinseed sunfish in Rat Cove, Otsego Lake.
131 bodies and report taster growth and larger sizes. This is shown by Deacon and Keast (1987) and Fox and Keast (1991) from five warm Ontario waters. ACKJ\JOWLEDGMENTS Many thanks go out to Mary Miner for her hard work and help in capturing fish. aging scales. and recording data. Thanks also to all the interns from 1994 to 1996 who aided in data collection. This study was supported by the Biological Field Station, Dr. Harman. and the OCCA. LTERATURE CTED Austin. E.. RC. MacWatters. W.N. Harman and RM. Harman. 1986. Age and growth ofeleven fish species in littoral areas of Otsego Lake. n 19th Ann. Rept. SUNY Oneonta Bio. Fld. Sta.. SUNY Oneonta. Pages 36-57. Casselman. J.M. 1987. Determination of age and growth. Pages 209-242. Chapter 7 in A.H. Weatherley and H.S. Gill. The biology offish growth. Academic Press. London. 433 pp. Danylchuk. A.J. and M.G. Fox. 1994. Age and size-dependent variation in the seasonal timing and probability ofreproduction among mature female pumpkinseed. Env. Bio. Fish. 39:119-127. Deacon. L.1. and J.A. Keast 1987. Patterns of reproduction in two populations of pumpkinseed sunfish with diftering food resources. Env. Bio. Fish. 19(4):281 296. foster. J.R. 1996. The fish fauna of Otsego Lake. n 28th Ann. Rept. SUNY Oneonta Bio. rid. Sta.. SUNY Oneonta. Pp. 202-220. Fox. M.G. and A. Keast. 1991. Eftect of ovenvinter mortality on reproductive life history characteristics of pumpkinseed populations. Can. J. Fish. Aquat. Sci. 48: 1792-1799. Jearld. A. jr. 1992. Age Determination. Pages 301-324. Chapter 16 in L.A. Nielsen and D.L. Johnson cds.. Fisheries techniques. 4th edition. American Fisheries Society. Bethesda. Maryland. 468pp. Lux. F.E. 1971. Age determination of fishes. U.S. Dept. of Commerce fishery Leaflet 637. 7pp. MacWatters. RC. 1983. The fishes of Otsego Lake. SUNY Oneonta Bio. Fld. Sta..
132 MacWatters, R.C. 1983. The fishes ofotsego Lake. SUNY Oneonta Bio. Fld. Sta.. SUNY Oneonta, Occasional Paper #15. 59pp. Regier, B.A. 1962. Validation of the scale method for estimating age and growth of bluegills. Trans. Am. Fish. Soc. 91:362-374. Scott W.B. and E.J. Crossman 1973. Freshwater fishes ofcanada. Bull. Fish. Res. Bd of Canada 184. 966pp. Trautman. M.B. 1981. The fishes of Ohio. Ohio State University Press. 782 pp.