Detailed Examination of Ichthyoplankton Seasonality from a High-Resolution Time Series in the Northern Gulf of Mexico during 2004-2006

Ichthyoplankton samples collected during monthly cruises (October 2004-October 2006) off the coast of Alabama were used to characterize taxon-specific larval fish seasonality for taxa representing 58 different families of fishes. Mean concentrations for total fish larvae peaked in the summer (August), while taxonomic diversity was generally highest during the spring and summer months (March-October). Taxonomic richness was generally highest during the late summer and early fall. Dominant taxonomic groups included unidentified anchovies (Engraulidae), sand seatrout Cynoscion arenarius, Atlantic bumper Chloroscombrus chrysurus, Atlantic croaker Micropogonias undulatus, Gulf menhaden Brevoortia patronus, tonguefishes Symphurus spp., unidentified gobies (Gobiidae), drums (Sciaenidae), and cusk-eels (Ophidiidae). Our characterization of larval fish seasonality for coastal Alabama largely agreed with results from a synthesis (published in 1988) of larval fish seasonality in the northern Gulf of Mexico. For most of the dominant taxa examined, our collections indicated a contracted seasonal distribution (i.e., larvae were collected during months that were central to the previously reported seasonality and less so at the endpoints of their temporal occurrence). However, most of the sciaenids examined had the opposite trend, suggesting expanded seasonal occurrences in the plankton. This first-order comparison of the timing of taxon-specific larval fish supply in the northern Gulf of Mexico provides a framework for examining climate-related temporal shifts in adult fish spawning patterns and larval fish seasonality.