Interactive effects of habitat selection, food supply and predation on recruitment of an estuarine fish |
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Authors: | P Levin Rachel Petrik John Malone |
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Institution: | (1) Department of Marine Biology, Texas A&M University –Galveston, P.O. Box 1675, Galveston, TX 77553–1675, USA, US |
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Abstract: | Seagrass meadows are often important habitats for newly recruited juvenile fishes. Although substantial effort has gone into
documenting patterns of association of fishes with attributes of seagrass beds, experimental investigations of why fish use
seagrass habitats are rare. We performed two short-term manipulative field experiments to test (1) the effects of food supply
on growth and densities of fish, and (2) effects of predation on the density and size distribution of fish recruits, and how
this varies among habitat types. Experiments were conducted in Galveston Bay, Texas, and we focused on the common estuarine
fish, pinfish Lagodon rhomboides. In the first experiment, replicate artifical seagrass and sand plots were either supplemented with food or left as controls.
Recruitment of pinfish was significantly greater to seagrass than sand habitats; however, we detected no effect of food supplementation
on the abundance of recruits in either habitat. Pinfish recruits in artifical seagrass grew at a significantly faster rate
than those in sand habitats, and fish supplemented with food exhibited a greater growth rate than controls in both sand and
artifical grass habitats. In our second experiment, we provided artificial seagrass and sand habitats with and without predator
access. Predator access was manipulated with cages, and two-sided cages served as controls. Recruitment was significantly
greater to the cage versus cage-control treatment, and this effect did not vary between habitats. In addition, the standard
length of pinfish recruits was significantly larger in the predator access than in the predator exclusion treatment, suggesting
size-selective predation on smaller settlers or density-dependent growth. Our results indicate that the impact of predation
on pinfish recruits is equivalent in both sand and vegetated habitats, and thus differential predation does not explain the
higher recruitment of pinfish to vegetated than to nonvegetated habitats. Since predators may disproportionately affect smaller
fish, and a limited food resource appears to be more effectively utilized by fish in vegetated than in unvegetated habitats,
we hypothesize that pinfish recruits may select vegetated habitats because high growth rates allow them to achieve a size
that is relatively safe from predation more quickly.
Received: 10 October 1996 / Accepted: 5 April 1997 |
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Keywords: | Seagrass Recruitment Predation Food limitation Lagodon rhomboides |
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