Geographic variation in the reproductive biology of the sand crab Emerita analoga (Stimpson) on the California coast

Abstract

Reproductive characteristics were measured in 23 populations of the sand crab Emerita analoga Stimpson in midsummer over ≈ 1000 km of the California coast. Significant geographic patterns were found in the female size at maturity, the size and age distribution of ovigerous crabs, and an estimate of population fecundity. No geographic patterns were found in egg size and size-specific fecundity. Crabs from southern sites reproduced at smaller sizes and younger ages and attained smaller maximum sizes than crabs from northern sites. Young of the year crabs at northern sites matured at larger sizes, reproduced in smaller proportions, and produced larger initial clutches than southern crabs. Size at maturity and the size distribution of ovigerous crabs were inversely correlated with water temperature. Fecundity was significantly correlated with crab carapace length in all populations but no geographic trend was found in size-specific fecundity. The lack of overlap in the size ranges of ovigerous crabs did not allow direct comparisons of fecundity-size regressions between northern and southern populations. The relationships of fecundity and crab size varied significantly among populations in both the northern and the southern groups. Estimates of population fecundity decreased significantly from north to south. That trend was related to geographic patterns in the size and age distribution of ovigerous crabs.