Consistent habitat segregation between sexes in the spider crabs Maja brachydactyla and Maja squinado(Brachyura), as revealed by stable isotopes

Abstract

Differences in the resource use patterns of males and females of the spider crab species Maja brachydactylaBalss, 1922 and M. squinado (Herbst, 1788) from several geographic areas (three in the Atlantic and two in the Mediterra-nean) were studied through the analysis of stable isotopes of carbon and nitrogen in the exoskeleton of post-pubertal (adult) specimens. Results confirmed that males and females from the same population usually did not differ in δ15N values and hence foraged at the same trophic level. In contrast, females were usually enriched in 13C as compared with males from the same population, thus suggesting that females use shallower habitats than males before the terminal moult. The results re-ported here also indicate that stable isotopes can be useful for the traceability of commercial Maja species, but only if species and sex are incorporated in the analysis.