Introduced clupeids in a southern reservoir: more evidence for system-specific reproductive styles

Abstract

SynopsisLatitudinal trends in reproductive characteristics are evident for some species of Clupeidae. However, selection for life history styles may operate at the population level. The reproductive cycles of alewife Alosapseudoharengus and threadfin shad Dorosoma petenense in Dale Hollow Reservoir, Tennessee, were monitored over two spawning seasons on the basis of a gonadosomatic index (GSI). Inshore movements normally associated with spawning migrations were monitored using gill nets in spring 1989. GSI values peaked for both species at least one month earlier in 1989 than in 1988 due to warmer water temperatures earlier in the year. Highest GSI values for female alewife occurred each year when surface water temperatures were about 20" C; threadfin shad GSI values peaked at temperatures of 22"-26" C. Trends in male GSI values in both species were similar to those in females. Alewives were not abundant in warm (> 22" C), shallow water after 1 May 1989, but alewife GSI values remained high after this date, suggesting that elevated inshore temperatures limited alewife reproduction. All aspects of alewife reproduction were comparable to other populations of alewife but did not follow latitudinal trends. Threadfin shad reproductive characteristics were similar to other published accounts. We suggest that thermal regimes and reservoir trophic status are important factors for clupeid reproduction and population-level analysis is suggested when considering reproductive styles. Further, our ability to predict the ecology of introduced species in freshwater systems is impaired when species considered have not coevolved or evolved in marine environments.

Sampling and Statistical Considerations for Hydroacoustic Surveys Used in Estimating Abundance of Forage Fishes in Reservoirs

“…We did observe higher densities in the upstream regions of the eastern arm (region 3) as well, although the pattern was far less pronounced when compared to the trend in the east-west direction. Habitat features, such as temperature and prey in these upstream regions, may have been favorable throughout the year as we observed high densities in December, which is outside the period of reported spawning by shad (Irwin and Bettoli 1995;Hale 1996).…”

Environmental Changes Affecting the Migratory Timing of American Shad and Sockeye Salmon

“…1959) and usually exerts a stronger control than temperature (Beacham and Murray 1988). Temperature exerts a stronger influence on maturation, relative to photoperiod, in most teleosts than in salmonids (Bye 1984), and clupeid reproductive schedules vary greatly from year to year in association with temperature (Irwin and Bettoli 1995). Salmonid oocytes remain viable in the body cavity for a longer period after ovulation than in most teleosts, and ovulation is controlled less strongly by immediate environmental conditions (Stacey 1984).…”

Ethmalosa fimbriata (Bowdich 1825), a Clupeid Fish That Exhibits Elevated Batch Fecundity in Hypersaline Waters

“…Females sampled at elevated salinities were producing four times more oocytes (294 ± 137 oocytes g −1 ) than their oceanic counterparts (74 ± 65 oocytes g −1 ). Clupeid fishes are known to adjust reproductive strategies to local conditions [7,64,65] and thus produce egg quantities and egg sizes that favour offspring survival under the environmental conditions in which they are to develop [66,67].…”