Growth Rates Of Predatory Fishes In Vegetated And And Unvegetated Habitats: Field Experiments With Juvenile Red Drum, Scianeops Ocellatus

Seagrass habitats have long been hypothesized to serve as nursery areas for juvenile fishes by providing food and refuge from predators. The objective of this study was to test this hypothesis in the field by comparing growth rates of juvenile red drum in seagrass beds to growth rates over an adjacent sand flat. Large (1.4 m2) enclosures were used to restrict juvenile red drum to a single habitat, and six drum were individually marked and stocked into each enclosure. Results from two studies during August 1988 and October-November 1988 indicated that growth rates in terms of weight, standard length, and total length of red drum were higher in sand enclosures than enclosures in shoalgrass (Halodule wrightii) . A third field experiment was conducted December 1988-February 1989 to compare growth rates of juvenile red drum among sand and vegetated areas by examining increase in otolith radius. Fish were immersed in calcein (200 mg/l) for four hours prior to stocking to produce a time-reference mark uithin their otoliths. No fish died due to marking. Preliminary examinations of calcein-marked otoliths indicate that this method is suitable for comparing growth rates of fishes in various habitats. Use of this technique to compare growth rates of fishes in different invironments will elucidate the relative value of critical nursery habitats and will contribute to understanding habitat selection by fishes.