Zooplankton, Fish and Sport Fishing Quality Among Four Alabama and Georgia Reservoirs of Varying Trophic Status

ABSTRACT

Four mainstream river impoundments located in Alabama and Georgia were examined in 1989 and 1990 to determine the response of zooplankton and fish to trophic gradient. Mean chlorophyll a concentrations ranged from 2 μg/L in the mesotrophic lake to 34 μg/L in the highly eutrophic lake. Two of the lakes were moderately eutrophic with mean chlorophyll a concentrations of 13 and 15 μg/L. Rotifer and total zooplankton densities increased with increasing trophic status, but crustacean zooplankton densities and biomass did not. Estimates of fish abundance and biomass were positively related to trophic state. Forage fish community structure in the mesotrophic lake was numerically comprised of Iepomid sunfish (47%), cyprinid minnows (20%) and shad (Dorosoma) (13%), but shad comprised 45% to 53% of the fish community in the eutrophic lakes. Black bass (Micropterus spp.) growth rates were similar in all lakes, however crappie (Pomoxis spp.) grew faster in the more eutrophic reservoirs. Fishing effort adjusted for lake size was positively related to trophic gradient. Total weight and number of fish harvested was highest in the most eutrophic lake, but highest harvest per unit effort occurred in the mesotrophic lake. Generally, larger fish were caught in the eutrophic lakes than in the mesotrophic lake, and angler-caught black bass size was similar among the three eutrophic lakes. Trophic gradient was not related to angler perception of fishing success nor to where anglers chose to hold their fishing tournaments. Reservoirs with mean growing-season (May-September) chlorophyll a concentrations between 10 and 15 μg/L may provide black bass and crappie fisheries that are similar to those fisheries of more productive lakes.

Key Words:

• trophic gradient
• tropic status
• fish
• zooplankton
• sport fishery
• reservoir
• lake
• fertility
• nutrient limitation
• retention time