Rg. Hartnoll et al., SIZE DISTRIBUTION IN SPIDER CRAB POPULATIONS - SPATIAL AND TEMPORAL VARIATION, Journal of crustacean biology, 13(4), 1993, pp. 647-655
The size distribution of the spider crabs Hyas coarctatus and Inachus
dorsettensis was investigated in several areas close to the Isle of Ma
n. Samples were collected in 1958-1959 and again in 1988-1990. One are
a was sampled during both periods. On both occasions each species disp
layed clear differences between areas in the size distribution of the
terminal instar. This is attributed to variation in the size at which
the terminal pubertal molt occurred; the contributions of genetic and
environmental factors to this variation are discussed. In prepubertal
specimens males exceeded females, but females predominated among postp
ubertal crabs. This swing in sex ratio is discussed. In the area sampl
ed in both periods, the abundance of each species declined to about a
fifth of that recorded 30 years ago. This is considered a result of he
avy scallop dredging throughout that interval. An expected decrease in
the size of the terminal instar was not observed, and, in fact, an in
crease occurred in Inachus dorsettensis. Possible explanations are con
sidered.