Estimating intermoult duration in Giant Crabs (Pseudocarcinus gigas)

Inter-moult duration in giant crabs (Pseudocarcinus gigas) was estimated by an alternative method to utilising tag-recovery data. Reproduction in female giant crabs occurs in annual cycles, although females occasionally “skip” a reproductive season and do not become ovigerous; it has been noted previously that this appears to be associated with molting. Thus the proportion of females that do not participate in reproduction may indicate the proportion molting. This approach was tried with a sample of 342 females and the number that were “skipping” a reproductive season was measured by computerized tomography scanning (CT-scanning) of their ovaries prior to the extrusion of eggs. Radiometric aging (228Th/ 228Ra) of carapaces was also undertaken with the focus of this work on testing an assumption of the method, rather than describing the intermolt duration of a population.