Ecological study on the frilled shark, Chlamydoselachus anguineus, with the other deep-sea elasmobranches, from Suruga Bay, central Japan

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The frilled shark, C. anguineus is the most famous deep-sea elasmobranch fish which is though as a devonian relict species and to be distributed in the deeoseas almost all the world. However, little or nothing is hitherto known on the life history on this shark of great interest. From January 1984 to December 1988, 242 specimens (116 females and 126 males) were collected by midwater trawl net and bottom gill-net which were towed or set at depths between 60 and 450m. Their total lengths and body weights ranged 125.6-181.0cm and 3670-17370g in females, and 117.8-155.9cm and 2780-6360g in males. Twenty adult sharks were reared for 7 days or shorter in an aquarium. Stomach contents in 139 specimens (77 females and 62 males) were squids (23 samples, 16.5%), fishes (4 samples, 2.9%), and undetermined sediments (1 sample, 0.7%). Sexual minaimal sizes were surmised to be at about 110cm in males and about 140-150cm in females and to have no limited reproductive season in the present C. anguineus. Ovulation occurred at a stage of 80-90mm in diameter of the ovarian eggs. Fertilization occurred at the capsulogenous gland and fertilzed eggs were developed in the capsule in the uterus in their early stages. Those embryos, on andafter reaching 80mm in total length, came out of the capsule and continued to develop in the uterus. Pups were born at about 550mm in total length. Four fertilized eggs with developing emmbyos in the capsule were reared for 134 days in natural sea-water in an small aquarium tank.