Fish predation on juvenile brown shrimp Penaeus aztecus Ives: the effects of simulated Spartina on predation rates
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The effect of artificial Spartina structure on the predation rates of four estuarine fish on juvenille brown shrimp (Penaeus aztecus Ives) was examined under laboratory conditions. Vegetative structure reduced predation rates of pinfish and Atlantic croaker, but did not affect predation rates of red drum and speckled trout. Pinfish and Atlantic croaker were inefficient predators, needing several strikes before sucessfully capturing prey. This inefficiency, necessitating repeated detection of prey organisms, probably contributed to the reduced predation rates by these fish in vegetated treatments. Although pinfish and speckled trout appeared to be strictly visual feeders, Atlantic croaker and red drum could apparently detect and feed upon shrimp through other sensory mechanisms. Differences in the mode of feeding among the fish, however, did not appear to be related to the effect of vegetative structure on predation rates. Over all of the experiments, predation rates on shrimp (50-69mm) ranged between approx. 2 and 13 shrimp/fish/day, and there was a positive relationship between the number of shrimp eaten and the size of the predator.