Early Life History of Prognichtys occidentalis and Caranx crysos Associated With Sargassus Habitat in the Northcentral Gulf of Mexico
Pelagic Sargassum and associated fronts provide an important combination of enhanced biological production and structural habitat in oceanic environments. Fronts are regions of convergence between two water masses and often provide enhanced prey densities for juvenile fishes. The present study examined the influence that this habitat has on the growth, feeding, and condition of larval and young juvenile blue runner Caranx crysos and bluntnose flyingfish Prognichthys occidentalis. Neuston tows were taken adjacent to fronts, and 1.6-3.2 km from each front in open water to serve as a reference. Sampling was conducted on each side of a front. Otolith increment analysis was performed, and analysis of covariance (ANCOVA) was used to determine the influence of habitat on growth rates. Stomach content analysis determined the influence of habitat on feeding success by means of ANCOVA. Diets were examined for each species and habitats using Morisita's and Shoener's Index. The influence of habitat on fish condition was determined by means of ANCOVA. Significant differences were found in the growth, feeding, and condition for these two species between habitats, although the directionality of the relationships was inconsistent. Variability in the results were likely caused by prey patchiness in the oceanic environment and suggests that Sargassum and associated fronts provide conditions for increased growth, feeding, and condition for many larval and young juvenile fishes.
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