Aspects of the biology of carcharhiniform sharks in Indonesian waters

Abstract

A total of 13 species of carcharhiniform sharks (excluding the families Carcharhinidae and Sphyrnidae) belonging to four families was recorded in fish landing site surveys in eastern Indonesia. Of these, the Triakidae were most abundant in the landings with Hemitriakis sp. 1 and Mustelus cf. manazo both contributing 1.8% to the total number of all sharks recorded. A number of the species, i.e. Atelomycterus baliensis, Halaelurus sp. 1, Hemitriakis sp. 1, Mustelus cf. manazo and Mustelus widodoi, were first recognized during these landing site surveys. A size at maturity for males of the two most abundant scyliorhinids, Atelomycterus marmoratus and Halaelurus sp. 1, could not be accurately determined, but they attained maturity at 419–506 and 360–404 mm TL, respectively. The latter species displays multiple oviparity with the uteri of pregnant females possessing six or 12 egg cases, each containing early to mid-term embryos. The length at first maturity (L₅₀) of males of Hemitriakis sp. 1 and M. cf. manazo was 900 and 859 mm TL, respectively, and the length at birth was approximately 280 mm TL in both species. The mode of reproduction in both of these species was viviparous, with histotrophy. The most abundant hemigaleid species, H. microstoma, was found to mature at a far larger size than the only other congeneric species H. australiensis, i.e. 750–780 vs 600–650 mm TL, respectively. The data presented in this paper are the first such biological data reported on six of these shark species and are thus vital for fisheries managers and conservation assessors, especially given the extent of the shark and ray fisheries in Indonesia.