Arthropods (Jun 2012)
Changes in population structure and body dimensions of two xanthid crabs: A long-term study in a single boulder-shore
Abstract
Two xanthid crab species were studied during 29 months over a period of 14 years between 1986 and 1999 all in exactly the same boulder shore. One of the crab species studied was the xanthid, Eriphia verrucosa (Forskall, 1775) with 60 specimens, the other species, Xantho poressa (Olivi, 1792), with 155 specimens. A significant change in numbers of both males and females of E. verrucosa was noticeable between 1986 and 1996 with a marked drop in numbers between these years. In 1997 male numbers increased again to almosttheir previous numbers in the population during 1986. The population of X. poressa declined significantly towards the end of the study period. Numbers of both genders peaked in spring and again, in summer. There was generally a decline in numbers of both crab species during autumn and winter. Thus, the average capture during the seasons was highest in spring for males of both E. verrucosa, and X. poressa. The body dimensions: mass, carapace length (CL) and width (CW) were measured in both xanthids. The aim of this long-term study was to determine whether temporal changes in the population structure and allometric changes in the dimensions of these crabs took place. Only such long-term observations could reveal these changes in population.
