THERMAL INFLUENCES ON LIFE-HISTORY TRAITS AND REPRODUCTIVE EFFORT OF INTRODUCED PUMPKINSEED SUNFISH LEPOMIS GIBBOSUS IN THE RIVER MOSELLE BASIN (NORTHEASTERN FRANCE)

摘要

The influence of local thermal regimes on juvenile growth rates, life-history traits, and reproductive effort of introduced populations of pumpkinseed Lepomis gibbosus was examined in 11 water bodies in the River Moselle basin (northeastern France). Female pumpkin-seed were collected during their reproductive period in mid-June in 2009 and 2010, and water temperature was assessed over a 12-month period in 2010. Annual thermal degree-days above 10 ℃ varied from 1529 in a headwater site to 2722 in the Mirgenbach Reservoir, heated by cooling water from a nuclear power plant. Mean age at maturity varied from 1.3 to 2.2 and was inversely related to annual thermal degree-days. The proportion of mature age-1 females also increased with temperature, but neither mean total length at maturity nor gonadosomatic index was related to waterbody thermal regime. Body size at the end of the first year of life was unrelated to thermal regime, but the growth rate of immature age-1 females in their second growing season was positively related to thermal degree-days in the spring. Wanner water bodies showed elevated reproductive effort in age-1 females when either early season gain in mass or mass at the beginning of the second growing season was controlled for; however, reproductive effort was unrelated to thermal regime in age-2 and age-3 females. Mean age at maturity was related to mean length at age 1 but not to mean length at age 2, in contrast to native North American and introduced European populations. We conclude that the life-history response of pumpkinseed to warmer temperatures occurs primarily in age-1 individuals and predict that climate wanning will produce changes in pumpkinseed life-history traits that will make the species more invasive in parts of Europe where the species is present but not actively spreading.