Reproductive biology of the crocodile shark Pseudocarcharias kamoharai

Abstract

From February 2005 to September 2007, a total of 490 crocodile sharks Pseudocarcharias kamoharai, caught as by-catch in the swordfish and tuna longline fishery that operates in the tropical western Atlantic Ocean, was studied in regard to their reproductive biology. Maximum observed total lengths (L(T)) were 1220 and 1090 mm for females and males respectively, with a high proportion of the catch being composed of mature specimens. Sexual maturity was attained at 760-810 mm L(T) for males (L(T50) = 800 mm) and 870-980 mm L(T) for females (L(T50) = 916 mm). The size at birth was estimated at 415 mm L(T). Temporal variation in gonad morphology and mass suggests that in this region P. kamoharai, an aplacental viviparous species with oophagy, does not show a well-defined reproductive seasonality, with mating and parturition occurring possibly over an extended period of the year. Mean +/-S.D. fecundity was estimated to be 3.9 (+/- 0.6) pups per reproductive cycle.

Biological observations on the crocodile shark Pseudocarcharias kamoharai

“…In this study, most gravid females were also found to have four embryos in uteri but two embryos and three embryos were also found. This was consistent with what Oliveira et al (2010) found in their study. No significant difference in embryo sex ratio from 1:1 was also consistent with that reported in the Atlantic Ocean (Oliveira et al , 2010).…”

“…The frequency of gravid P. kamoharai was as high as 60%. Oliveira et al (2010) also found that a high proportion of P. kamoharai catch was composed of mature individuals in the Atlantic Ocean. A high proportion of mature and gravid P. kamoharai caught indicates a need for caution as pelagic longline fisheries might greatly influence spawning stock biomass and recruitment of this species.…”

“…The female P. kamoharai sampled were significantly larger than males. Oliveira et al (2010) found that females attained larger sizes than males in the Atlantic Ocean. They pointed out that this might indicate sexual dimorphism in terms of maximum size, or might be the result of segregation in the population or sampling bias resulting from fishing selectivity.…”

“…In spite of its worldwide distribution, P. kamoharai has been poorly studied and little is known about its biology (Compagno, 2001; Oliveira et al , 2010). No biological study has been reported for P. kamoharai in the Indian Ocean.…”

“…Prior to this study, the biology of P. kamoharai had not been studied in international waters of the tropical Pacific Ocean, although observation on embryos of this species was reported for the central Pacific Ocean in 1980s (Fujita, 1981). Limited life‐history information hinders scientific assessments of population trends (Oliveira et al , 2010) and risk assessment (Cortés et al , 2010) for this species. The objective of this study was to analyse and quantify biological information on P. kamoharai , especially for pregnant females, in the tropical eastern Pacific Ocean.…”