Feeding selectivity and standing stocks of Fundulus grandis in an artificial brackishwater pond, with comments on Cyprinodon variegatus.
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The gut contents of fish from naturally-reproducing populations of dominant Gulf coast marsh cyprinodonts, sheepshead minnow (Cyprinodont variegatus) and gulf killifish (Fundulus grandis), F. grandis (N 47) showed greatest feeding selectivity for larval grass shrimp and crab parts. Large fish consumed primarily crabs and algae; smaller fish ate fine substrate, plant material, and amphipods. C. variegatus of all sizes (N 10) consumed filamentous algae and fine substrates. Major energy pools in the pond with fish were filamentous algae, small amphipods, molluscs and fish; and in the fish-less pond widgeon grass (Ruppia maritima), large crustaceans (gammarid amphipods and crabs), and molluscs. Pond biota supported approximately 12,800 C. variegatus (19.4 kg) and 1,100 F. grandis (4.8 kg). Phytoplankton production in the pond with fish was twice that in the fish-less pond. Widgeon grass occupied 30% of fish-less pond, but was absent in the presence of fish. Several food items selectively eaten in the stocked pond were more abundant in the fish-less pond.