INTRODUCED CLUPEIDS IN A SOUTHERN RESERVOIR - MORE EVIDENCE FOR SYSTEM-SPECIFIC REPRODUCTIVE STYLES

Latitudinal trends in reproductive characteristics are evident for som e species of Clupeidae. However, selection for life history styles may operate at the population level. The reproductive cycles of alewife A losa pseudaharengus and threadfin shad Dorosoma petenense in Dale Holl ow Reservoir, Tennessee, were monitored over two spawning seasons on t he basis of a gonadosomatic index (GSI). Inshore movements normally as sociated with spawning migrations were monitored using gill nets in sp ring 1989. GSI values peaked for both species at least one month earli er in 1989 than in 1988 due to warmer water temperatures earlier in th e year. Highest GSI values for female alewife occurred each year when surface water temperatures were about 20 degrees C; threadfin shad GSI values peaked at temperatures of 22 degrees-26 degrees C. Trends in m ale GSI values in both species were similar to those in females. Alewi ves were not abundant in warm (> 22 degrees C), shallow water after I May 1989, but alewife GSI values remained high after this date, sugges ting that elevated inshore temperatures limited alewife reproduction. All aspects of alewife reproduction were comparable to other populatio ns of alewife but did not follow latitudinal trends. Threadfin shad re productive characteristics were similar to other published accounts. W e suggest that thermal regimes and reservoir trophic status are import ant factors for clupeid reproduction and population-level analysis is suggested when considering reproductive styles. Further, our ability t o predict the ecology of introduced species in freshwater systems is i mpaired when species considered have not coevolved or evolved in marin e environments.