Growth, morphology and life history traits of a cool-water European population of pumpkinseed Lepomis gibbosus

Abstract

We examined attributes of growth, reproduction, morphology and diet of a population of pumpkinseed Lepomis gibbosus introduced into a cool-water pond (Cottesmore) in southern England, and compared them with available data on warm-water European populations. Morphologically, Cottesmore pumpkinseed appear to have a more streamlined body than the two southerly populations for which data are available, but this may be due to the small body size of the Cottesmore population. Ontogenetically, 11 morphological characters grew isometrically, 12 allometrically, and 3 split-isometrically (i.e. a significant shift in proportional growth rate); however, the split 'break points' (between 49 and 60 mm SL) do not appear to correspond with any change in resource use or in biological process. Juvenile and age-specific growth were the lowest reported of any European population, and mean GSI was also low. Growth rate was highest in May and June, with condition highest in June, and with peak GSI in June and July. Mean age at maturity in the Cottesmore population was the highest reported in Europe. Dietary overlap was high amongst most age classes, and there was evidence of cannibalism in the population. Late maturity of the Cottesmore population was probably the result of relatively low temperatures during the growing season, slow growth, poor condition at age 3 (due to limited food resources), and intensive egg predation by high numbers of juveniles, giving a fitness advantage to late-maturing females.