Distribution of carangid larvae (Teleostei: Carangidae) and concentrations of zooplankton in the northern Gulf of Mexico, with illustrations of early Hemicaranx amblyrhynchus and Caranx spp. larvae

Abstract

We examined 1,825 bongo-net samples collected during Southeast Area Monitoring and Assessment Program (SEAMAP) ichthyoplankton surveys of United States Gulf of Mexico waters (1982–1986) for carangid larvae. Objectives were to describe the distribution of carangid larvae and to examine distribution patterns relative to areas of higher zooplankton volumes in order to reveal areas that may be important nurseries. Samples contained about 29,200 carangid larvae from 13 species or species complexes in 11 genera. Chloroscombrus chrysurus and Decapterus punctatus accounted for 91.7% of all larvae. We found that the ‘scads’ (D. punctatus, Trachurus lathami, and Selar crumenophthalmus) utilize temporally and/or spatially distinct spawning strategies to reduce co-occurrence of larvae. Samples contained fewer larvae than expected of the amberjacks (Seriola spp.), Caranx crysos, and C. hippos/latus given the abundance of adults in the survey area, possibly due to inadequate sampling at appropriate times and locations, gear avoidance, or gear bias. Zooplankton displacement volumes (ZDVs) differed among regions and seasons and were inversely related to surface salinity and station depth. Differences among years were not significant. ZDVs were consistently highest near the Mississippi River delta and along the western Louisiana/eastern Texas shelf, and moderately high during summer and fall along the shelf break, with localized pockets of elevated volumes over the eastern Gulf shelf. We suggest that Chloroscombrus chrysurus, D. punctatus, T. lathami, and possibly Oligoplites saurus, Hemicaranx amblyrhynchus and Caranx crysos spawn in frontal areas and/or along other hydrographic features that promote higher productivity. We provide new illustrations and descriptive information for the larvae of H. amblyrhynchus and discuss characters that separate early larvae of several species of Caranx.