Food Habits and Diet Overlap of Larval Lepomis spp. and Gizzard Shad in a Piedmont Reservoir

The food habits of larval Lepomis spp. and gizzard shad (Dorosoma cepedianum) in Hyco Reservoir, North Carolina, were studied during 1982. Results indicated that Lepomis spp. began feeding at a length of 4 mm on copepod nauplii and the rotifers Polyarthra and Filinia. Selection later (10 mm) shifted to Bosmina, Daphnia, and Mesocyclops, while Diaphanosoma was strongly selected for by all sizes of larvae. The crustaceans Diaptomus, Ceriodaphnia, and Holopedium, along with most rotifers, were not selected. Gizzard shad began feeding primarily on large phytoplankters at 4 mm, then shifted to nauplii and Polyarthra at 5 mm, then to Daphnia at 12 mm. Bosmina and Diaphanosoma were eaten occasionally; and Diaptomus, Ceriodaphnia, Holopedium, and most rotifers were not selected. Both fish species ate significantly greater amounts of zooplankton during the day than at night, and Lepomis spp. ate significantly more zooplankton than gizzard shad overall. A niche overlap index indicated that there is some competition and diet overlap only among small (5-6 mm) Lepomis spp. and gizzard shad larvae. Diet overlap then decreased with increasing fish size, and densities of the principal zooplankton prey items were sufficiently great to permit resource sharing among these predators.

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