Influence of Trophic Status on Larval Fish Abundance in Four Southeastern United States Reservoirs

Abstract

ABSTRACT While the relationship between productivity and adult fish yield has been extensively studied, it has been viewed as a static relationship, whereas interactions among organisms and trophic levels change dramatically with the life stage of the interacting organisms. As such, little attention has been given to mechanisms that might control this relationship. Toward this end, we examined the influence of trophic status on larval fish abundance in four reservoirs in Alabama and Georgia, USA. Larval fish communities in eutrophic reservoirs were dominated by gizzard shad (Dorosoma cepedianum) and threadfin shad (D. petenense), while crappie (Pomoxis spp.) and sunfish (Lepomis spp.) contributed a relatively larger percentage of the fish community in the oligotrophic reservoir, similar to findings for older fishes from previously published work. However, while larval shad and lepomid sunfish were more abundant in eutrophic than in oligotrophic reservoirs, larval crappie showed the opposite trend. Why larval shad and lepomid sunfish appeared to be controlled by lower trophic levels while larval crappie appeared to be controlled by upper trophic levels was not clear. However, when our larval fish abundance results were compared with previous results for older fishes, they suggest that while the mechanism controlling abundance and eventual year-class strength may differ across species, actual abundance and year-class strength within species is likely set during early life.