Physiological performance of largemouth bass related to local adaptation and interstock hybridization: implications for conservation and management

Abstract

Four genetically distinct stocks of age 2+ years largemouth bass Micropterus salmoides were produced using adults collected from two regions in the upper midwest (central Illinois, IL and south‐eastern Wisconsin, WI, U.S.A.). Two pure stocks (IL × IL and WI × WI), as well as both of their reciprocal F1 interstock hybrids (IL × WI and WI × IL) were produced in research ponds in Champaign, IL. In general, swimming performance, routine oxygen consumption and activity were highest at 18 × C, intermediate at 12 × C, and lowest at 6. C for all stocks. However, performance indicators varied among stocks at each of the temperatures. The pure Illinois stock (IL × IL) had the lowest activity: cost ratio at 18 × C and the highest at 6_ C (based upon swimming strength, routine activity rates and routine metabolic rates). The opposite pattern was observed for the other pure stock (WI × WI). Although differences were less distinct at lower temperatures, the two pure stocks (IL × IL and WI × WI) outperformed both interstock hybrids. These results indicate that not only do non‐native stocks appear to have reduced performance relative to locally adapted stocks, but also that interstock hybrids exhibit performance impairments, not hybrid vigour.