Spatial temporal scales of patches of crab larvae in coastal waters

Abstract

This study examined the spatial and temporal scales of patches of crab larvae in the coastal waters of the Middle Atlantic Bight near the mouth of Delaware Bay, USA (38.70° N, 75° W). The spatial scale of the patches was characterized by sampling along-shelf and across-shelf transects via series of continuous plankton tows. Autocorrelation of larval densities along each transect revealed that patch diameters ranged from about 0.5 to 2.5 km in both along-shelf and across-shelf dimensions. The ages of 12 different patches were estimated by comparing the proportions of Stage I and Stage II larvae composing each patch. One additional patch was tagged with a satellite-tracked drifter, and changes in the proportions of the 2 stages were observed over a 3 d period. Analysis indicated that the tagged patch had remained cohesive for at least 4 d and possibly as long as 6 d. Potential mechanisms for patch formation and maintenance include synchronous spawning events, associative larval behavior, and aggregative physical processes.