Size -fecundity relationships, mating behaviour, and larval release in the New Zealand paddle crab, ovalipes catharus (white 1843) (Brachyura: Portunidae)

Abstract

A logarithmically increasing relationship was found between fecundity (F) and carapace width in mm (CW) [Ln(F) = 1.81439 + 2.44173 × Ln(CW)] with a slightly better statistical fit being produced with an exponential relation [Ln(F) = 9.79540 + 0.03325 × CW]. The relation between fecundity and drained body weight in g (BWg) was equally well described by both a simple linear relation [F = 25630.76 + 2552.12 × BWg], and a logarithmic relation [Ln(F) = 8.58960 + 0.85978 × Ln(BWg)]. Although all curves were highly statistically significant the precision of prediction was limited as a wide range of fecundities was observed for any given size. Large females (100 mm) would have an expected fecundity per batch of eggs of approximately 500 000. No relation was found between mean egg size and carapace width, nor were there significant relations between development stage and egg size, or between development stage and fecundity. Male paddle crabs carry pre‐moult females for up to eight days prior to the female moulting. Females were carried with their dorsal surface against the males ventral surface, grasped either by the males second or third walking legs. After she moults the pair copulate, generally for between 12 and 36 hours (but up to four days), before the female is released. Guarding during copulation protects females from cannibalism. Females adopted an elevated posture on the tips of their limbs and used vigorous sweeping and flushing motions when releasing larvae. © The Royal Society of New Zealand 1994.