Gray Triggerfish, Balistes Capriscus, Reproductive Behavior, Early Life History, and Competitive Interactions Between Red Snapper, Lutjanus campechanus, in the Northern Gulf of Mexico
Type of DegreeDissertation
Fisheries and Allied Aquacultures
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Gray triggerfish, Balistes capriscus, is a widely distributed species, important to both commercial and recreational fisheries. Other species of Balistidae display atypical behaviors compared to most other marine fishes such as demersal spawning and unusually long periods in the plankton as juveniles. However, for gray triggerfish there is limited documentation on spawning behavior, early life history, and interactions with other species. To examine these aspects of gray triggerfish, spawning behaviors were recorded in June and July 2004 to 2007 on artificial reefs in the northern Gulf of Mexico by SCUBA diver observation and unattended remote video. A single male gray triggerfish established a territory around a reef, built 1 to 13 demersal nests in the sand, and attracted 1 to 5 female gray triggerfish to spawn. Eggs were collected from 13 of the 28 active nests and mean clutch size was 772,415 eggs. Based on male to female sex ratios, gray triggerfish displayed harem spawning behavior, with a single dominant male who attracted up to five spawning-condition females. Second, gray triggerfish larval development was described from laboratory-reared fish up to 6 d post hatching. Photographs of live larvae (N = 10) were taken daily to document development. Third, recruitment of age-0 gray triggerfish to benthic artificial reefs was documented by diver surveys from 2003 to 2007. Divers counted and estimated sizes of all gray triggerfish that recruited to three types of artificial reefs ranging in area from 1.2 to 4.0 m2. Peak recruitment of age-0 gray triggerfish occurred from September through December 2003-2007. Fourth, competitive interactions between gray triggerfish and red snapper were studied in field removal and laboratory growth experiments. In the field, gray triggerfish removal experiments were completed to test for effects on red snapper. After removals, size frequency distributions of red snapper were significantly different between triggerfish removed and triggerfish not removed treatments. In the laboratory, growth rates were compared between control red snapper and red snapper mixed with gray triggerfish. Red snapper showed a significantly slower growth rate when mixed with gray triggerfish compared to red snapper control. Field and laboratory studies provided evidence of competitive interactions between these species. These studies documented the ecology of gray triggerfish reproductive behavior, described larval development, seasonality and size of benthic recruitment, and competitive interactions with red snapper.