DEPTH-STRATIFIED POPULATION STRUCTURE OF GERYONID CRABS IN THE EASTERN GULF OF MEXICO

Abstract

ABSTRACT Manned submersible transects and synchronous trap-sampling were conducted in the eastern Gulf of Mexico along 5 depth contours on the upper continental slope, during September 1986 and 1987. Female golden crabs, Chaceon fenneri, were more abundant at 350 m and 445 m than at 550, 675, or 780 m. Male golden crabs were most abundant at 550 m. On the average, the largest crabs of each sex were caught near 350 m. More mated pairs (50%) were observed in situ along the deepest 2 contours than expected by chance alone. Within the bathymetric range of golden crabs, crab abundance may be related more to habitat type than to depth. The greatest density (36.5 crabs/ha) occurred on or near hard-bottom canyon features. Red crabs, Chaceon quinquedens, occurred only at 675 m and 780 m on heavily bioturbated soft sediments, with the largest of each sex at 675 m. Male red crabs outnumbered females, but depth did not affect the number caught. Golden and red crabs also differed in their refuging habits and responses to being disturbed. We suggest that bathymetric patterns in sex and size within geryonid populations reflect, in part, severe male-male competition for mates and alternative mating strategies for males.