COOKE, SJ; PHILIPP, DP; University of Illinois; Illinois Natural History Survey: Physiological Consequences of Translocation and Interstock Hybridization of a Freshwater Teleost Fish

The cardiovascular response to exhaustive exercise among differentiated stocks of largemouth bass was compared at 10°C and 20°C as an assessment of local adaptation and interstock hybridization. Cardiac parameters (both resting and maximal) were consistently lowest for pure locally adapted fish relative to the translocated pure fish or all interstock hybrids, although cardiac scope remained consistent. Furthermore, when exposed to exercise, cardiac parameters for locally adapted pure fish returned to resting levels more rapidly than other stocks. Energetics simulations revealed that due to the elevated metabolic rates in interstock hybrids, net growth rate would be reduced by more than half relative to locally adapted pure fish. When we tested for the influence of different genetic and geographic distances on outbreeding depression, MtDNA data (genetic distance) was infrequently identified as a significant source of variation in cardiovascular performance. However, genetic distance data for allozymes revealed that they play an important role in the determination of resting cardiac values, particularly, heart rate. Latitude (geographic distance) accounted for between 31 and 45 % of variation observed in the recovery parameters.