PARENT SESSION
Oral Session #61: Aquatic Ecology: Fish - Communities and interactions. Presiding: J. Chick.
Thursday, August 9, 2001. 8:00 AM to 11:45 AM. Hall of Ideas F.
Fish recruitment in reservoirs: Quantifying the interactive effects of depth, turbidity, and zooplankton.
AREND, KRISTIN1, DOHERTY, CHAD1, STEIN, ROY1, BREMIGAN, MARY2, 1 2
ABSTRACT- We explored how turbidity, light intensity, and zooplankton size structure influence depth distribution and foraging success of larval bluegill, crappie, and gizzard shad among Ohio reservoirs spanning a productivity gradient. We hypothesized that (1) larval bluegill and crappie are at a greater foraging disadvantage than larval gizzard shad when turbidity is high and zooplankton are small; and (2) high turbidity reduces optimal foraging area and concentrates fish in surface waters. We sampled upstream and downstream within three reservoirs (mesotrophic to highly eutrophic) weekly during May through July 2000. Larval fish, zooplankton, turbidity, light intensity, and other abiotic variables were sampled at 1.0-meter (m) intervals to a depth of 5 m. Across reservoirs, 80% of larval gizzard shad and bluegill occurred within the top 2 m, whereas at least 50% of larval crappie occurred below 2 m depth. As reservoir productivity, and hence turbidity, increased, the proportion of gizzard shad at 1 m increased, and the proportion of crappie switched from being highest at 3 m to 1 m. Zooplankton distribution across depth, species interactions, and species-specific ontogenetic movement patterns will be included in a multivariate analysis to assess their impact on fish recruitment in Ohio reservoirs.
KEY WORDS: depth distribution, larval foraging, turbidity, zooplankton