Growth, Density, and Interspecific Influences on Pumpkinseed Sunfish Life Histories

Abstract

I collected data on 27 pumpkinseed (Lepomis gibbosus) populations in eastern and central Ontario and conducted a transplant experiment with one of these populations to test growth and competition—related predictions of several life history models. The predictions are that early maturity and high gonadal investment will occur: (1) in large and fast—growing juveniles; (2) in populations with low adult: juvenile growth ratios; (3) in populations with low density; and (4) in the absence of bluegill sunfish (Lepomis macrochirus), a competing congener. Predictions 1 and 4 were fully supported and Prediction 2 was partly supported, but Prediction 3 was not. The earliest maturing juveniles within populations were significantly larger than conspecifics of the same age that did not mature. Females from a lake population that were transplanted into a fishless pond exhibited both significantly faster growth and a significantly higher gonad to body mass ratio (gonado—stomatic index) that females living in the lake. At the population level, juvenile growth was significantly correlated with age at maturity (r = 0.52), but not with gonadostomatic index, whereas the Adult : Juvenile Growth Ratio showed a significant, negative correlation wih gonadosomatic index (r = 0.66), but not with mean age at maturity. Mean age at maturity showed a stronger correlation with the indicator of life—span and adult survival rate (r = 0.74), suggesting that mortality is more important than growth in the shaping of reproductive life histories of pumkinseed. High population density was associated with early maturity and high gonadal investment, the opposite of what was predicted. However, pumpkinseed populations that co—occurred with bluegills did mature significantly later and at a larger size and tended to have a lower gonadal investment than populations living in waterbodies without bluegills. This difference in reproductive patterns in the presence of bluegill is consistent with two—stage life history theory and may be the result of a direct effect of bluegills on pumpkinseed growth and survivorship, as well as differences in environmental conditions were the two species do or not co—occur.

Different life-histories of native and invasiveNeogobius melanostomusand the possible role of phenotypic plasticity in the species’ invasion success

“…where α is the mean SL at maturity, x is the size in mm, f(x) is the proportion of fish mature at size x, and w is the maximum size in the sample (DeMaster, 1978;Fox, 1994).…”

Age and growth in a newly-established invasive population of topmouth gudgeon

“…The curves were fitted using R software [15]. Mean age at maturity was calculated from the percentage of mature females and males in each size-class using the formula of DeMaster [16] as adapted by Fox [17]:…”

Annual development of gonads of pumpkinseed, Lepomis gibbosus (Actinopterygii: Perciformes: Centrarchidae) from a heated-water discharge canal of a power plant in the lower stretch of the Oder River, Poland

“…The course and duration of spawning of this species depend mainly on the photoperiod and temperature (Miller 1963), with temperature being the more important factor (Burns 1976). In the natural range of distribution, the pumpkinseed spawning season lasts from mid-May until July, and in some reservoirs, until the beginning of August (Breder 1936, Burns 1976, Fox 1994Danylchuk andFox 1994, 1996). As regards the European populations, the spawning season in Slovakia lasted from the end of May until the end of June (Holčik 1995), in Greece-from the second half of June until the end of July (Neophitou and Giapis 1994).…”

“…In the majority of studies, the information on the reproductive cycle was based on the values of gonadosomatic index (GSI) (Fox and Keast 1991, Danylchuk and Fox 1994, Neophitou and Giapis 1994, Dembski et al 2006, Santos et al 2012) and concerned mainly females (Fox 1994, Fox and Crivelli 1998, 2001). Other studies were based on the observations of the morphology of gonads (Deacon and Keast 1987), changes in gonad weight (Dembski et al 2006), nesting (Danylchuk andFox 1994), or the size distribution of larvae Moreno-Amich 1998, 2000). The aim of this study was to determine the annual cycle of gonad development in the pumpkinseed individuals from the self-sustained population living in the warm-water canal discharge canal of the Dolna Odra power plant, using histological analyses.…”