Patterns of habitat use by fishes associated with Sargassum mats in the Gulf of Mexico, with an emphasis on the greater amberjack (Seriola dumerili)

Abstract

Distribution and abundance of fishes associated with Sargassum mats in the NW Gulf of Mexico were examined off northern (Galveston) and southern (Port Aransas) Texas from May-August, 2000. A total of 37 species (17 families) was identified from larval purse seine collections. Individuals from seven species composed over 97% of the catch: planehead filefish (Monacanthus hispidus), blue runner (Caranx crysos), gray triggerfish (Balistes capriscus), chain pipefish (Syngnathus louisianae), sergeant major (Abudefduf saxatilis), sargassum fish (Histrio histrio), and greater amberjack (Seriola dumerili). Sizes were variable throughout the sampling period; however, over 95% of the species collected were in the early life stages. Temporal patterns were observed for several taxa; M. hispidus, S. louisianae, and H. histrio were more abundant in early summer (May-June), while C. crysos and A. saxatilis were more prominent late in the season (July-August). Abundance of dominant taxa was higher in northern waters and both abundance and diversity increased as a function of distance from shore. Distribution, age, and growth of young-of-the-year (YOY) greater amberjack Seriola dumerili associated with pelagic Sargassum were examined offshore Galveston, TX in the NW Gulf of Mexico. A total of 181 S. dumerili (33-210 mm SL) was collected from May to July of 2000 and 2001. Temporal patterns of habitat use showed relative abundance of S. dumerili was greatest early in the season (May and June). In addition, spatial patterns indicated that abundance in the offshore zone (CPUE, 7.60 ±3.6) was greater than the inshore zone (CPUE, 1.27 ±0.5). Ages of S. dumerili ranged from 35-150 days and hatch-date analysis indicated that the majority of spawning occurred from February to April. Average daily growth rates were 1.45 mm d⁻¹ throughout the sampling period, while both spatial and temporal differences in growth rates were observed. Mortality estimates were 0.0045 (0.45% d⁻¹) for S. dumerili between 40 and 139 days of age. Results of this study suggest pelagic Sargassum serves as nursery habitat and may influence the recruitment success of several species, particularly S. dumerili.