Aspects of reproduction and food habits of the Japanese swellshark Cephaloscyllium umbratile from Choshi, Japan.

Abstract

I examined 356 specimens of the Japanese swellshark caught off Choshi, near Tokyo, Japan. The Japanese swellshark Cephaloscyllium umbratile attained maturity at a total length of 861-880mm size class for males and 921-940mm for females. All males over 960mm and females over 1040mm were mature. The largest male (1140mm) was only slightly smaller than the largest female (1145mm). In males, both clasper length and testes weight increased rapidly with the onset of maturity. Occurrence of ripe ova or egg cases in females and presence of semen in the seminal vesicle of males throughout the year, as well as the lack of seasonal changes in male gonad indices indicate that C. umbratile does not have a well-defined reproductive season. Food items of the shark consisted of at least 71 prey species, principally fishes. Pacific mackerel and Japanese sardine were the dominant prey. Ten species of Chondrichthyan fishes were also important in their diet.