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Predation on sand dollars by gray triggerfish, Balistes capriscus, in the northeastern Gulf of Mexico

1991; Rosenstiel School of Marine and Atmospheric Science; Volume: 48; Issue: 1 Linguagem: Inglês

1553-6955

T. K. Frazer, William J. Lindberg, Gregg R. Stanton,

Marine animal studies overview

Triggerfishes (family Balistidae) feed diurnally (Randall, 1968) and are particularly adapted to prey upon hard-shelled invertebrates (e.g., molluscs and echinoderms) which are consumed by few other reef-dwelling fishes. As described by Randall (1968), triggerfishes have long snouts, terminal mouths, and short, strong jaws. Fricke (1971, 1975) described behavioral mechanisms by which Pseudobalistesfuscus (reported as B.fuscus) feeds on a sea urchin, Diadema sp., in the Red Sea. By jetting water against urchins, P. fuscus turns them upside down to expose the vulnerable oral side. We have observed gray triggerfish, Balistes capriscus, in the northeastern Gulf of Mexico, grasp spines of the urchin Arbacia punctulata between its teeth, flip the urchin over and attack its exposed underside to feed on soft tissue within. Randall (1967) described similar spine grasping behavior for B. vetula feeding on D. antillarum in the West Indies. Although sea urchins may be the major food source for B. vetula (Randall et aI., 1964; Randall, 1967), triggerfishes exploit a variety of prey species (Hobson, 1965; Randall, 1967; Aiken, 1975; Reinthal et aI., 1984). In the absence of D. antillarum, the diet of queen triggerfish shifted to crabs and chitons (Reinthal et aI., 1984). Reinthal et ai. (1984) suggested that B. vetula uses various behaviors to access prey in different habitats, including water jets to expose sand-dwelling organisms. Hobson (1965) observed B. verres, in the Gulf of California, feeding on sand-burrowing invertebrates after exposing them with jets of water from the mouth. Fricke (1971, 1980) inferred similar behavior for P.fuscus in the Red Sea, but did not describe it. Gray triggerfish, B. capriscus, were seen foraging over sandy bottom as we nondestructively censused motile reef-associated species, including B. capriscus, at reefsites west of Cedar Key, Florida, in the northeastern GulfofMexico (Lindberg et aI., 1990; Frazer and Lindberg, unpubl.). Based on observations of dozens of triggerfish at four sites over 18 months, we describe how B. capriscus locates and feeds on three common species of sand dollars, Mellita tenuis (=Mellita quinquiesperforata var. tenuis, see Harold and Telford, 1990, for recent taxonomic revision), Leodia sexiesperjorata and Encope michelini. As a consequence of this behavior, and given well known halo effects and habitat linkages from off-reef foraging (Ogden et aI., 1973; Parrish, 1989), one would expect the abundance of live sand dollars to increase with distance from reefs occupied by gray triggerfish. Here we confirm that prediction.