Figure 29.3. Mean growth rate in weight (GW)± STD of young-of-the-year winter flounder, tautog, and Atlantic tomcod caged under piers and in adjacent habitats in the lower Hudson River based on data collected in 1994, 1996, 1997, and 1998.

that occur there less frequently, and indeed, growth observations supported that theory. However, the data also suggested that while YOY Atlantic tomcod could grow in under-pier habitats, growth was lower than at edges or in open water. Therefore, we concluded that under-pier areas were unsuitable habitats for YOY winter flounder and tautog, and low-quality habitats for Atlantic tomcod relative to edges or open water. It was still not clear why piers had these negative effects, but it seemed unlikely that factors associated with pilings themselves were responsible because growth rates in pile fields (pilings without decking) were similar to growth rates in open water.

Why could Atlantic tomcod grow better under piers than winter flounder or tautog? We formulated two hypotheses to address this question: 1) Atlantic tomcod were better able to forage in low light and therefore could locate more food than winter flounder or tautog, or, 2) Atlantic tomcod consumed a different food source than the other two species. Winter flounder and tautog consume primarily benthic organisms as prey (Pearcy, 1962; Grover, 1982) butpreviousworkonjuvenileAtlantic tomcod suggested that individuals <90 mm TL consumed primarily planktonic prey types (Grabe, 1978). The Atlantic tomcod used in these experiments were in this size range (44-91 mm TL), therefore, the hypothesis that they utilized a different food source seemed likely. We examined the stomach contents of the caged fish to determine whether the diets among the three test species were dissimilar. We also used the data to compare the feeding habits of each species under, at the edge, and outside of the pier.

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