Biological aspects of silky shark Carcharhinus falciformis in the eastern Arabian Sea

Abstract

Reproduction, diet and growth of silky shark Carcharhinus falciformis in the eastern Arabian Sea are described based on 473 specimens collected from the gillnet-cum-longline landings at the Cochin fisheries harbour during 2012–2014. The reproductive biology of 215 males and 258 females was examined while 113 stomachs were sampled to study the diet. The von Bertalanffy growth parameters estimated using length-based models were asymptotic length (L∞) = 309.80 cm, growth coefficient (K) = 0.10 year−1 and age at zero length (t0) = −2.398 year. The sex ratio was significantly skewed to females. Seasonality in reproduction was not evident and in males, sexual maturity was attained at 201–223 cm total length (LT) with the size at maturity (LT50) occurring at 217.0 cm, whereas in females sexual maturity was attained at 224–231 cm LT and LT50 occurs at 226.5 cm. In total 114 embryos, in the length range of 12.2–65.1 cm were recovered from 15 pregnant females. Numbers of embryos in females were in the range of 3–13, averaging 7.6. Silky sharks of the eastern Arabian Sea feed primarily on swimming crab Charybdis smithii, with juveniles feeding principally on swimming crabs, while adults feed on actively swimming prey like squids and teleost fishes. This preliminary information on the reproduction, diet and growth should be useful to identify management strategies for silky sharks in the eastern Arabian Sea.

Catch Composition, Seasonality and Biological Aspects of Sharks Caught in the Ecuadorian Pacific

“…However, the size range of this study closely resembles to what was reported in the Central-Western Pacific in 2014 (65-271 cm TL) [9]. The sexual proportion was skewed towards females, which coincides with what was reported by Hoyos-Padilla et al [61] and Varghese et al [62]. However, it differs from other studies [15,63,64], where they found no difference in abundance between females and males.…”

“…The maturity size for males was 182.10 cm TL, which was very similar to that recorded in the Central-Western Pacific (183 cm TL) [9], in the Mexican South Pacific (180 cm TL) [63] and on the West Coast of Baja California Sur (182 cm TL) [61]. However, the maturity size seems to be bigger in the Eastern Indian Ocean (207.6 cm TL) [64], in the Eastern Arabian Sea (218.98 cm TL) [62] and in Campeche Bank (225 cm TL) [60]. These results suggest that males of Carcharhinus falciformis reach sexual maturity at a smaller size in the Pacific.…”

“…This present study reported a greater size range (83-341 cm TL) than the ones in eastern Indonesia (130.8-310 cm TL) [80], in the Eastern Arabian Sea (97-269 cm TL) [62] and in the southeastern Pacific Ocean (75.5-240 cm TL) [78]. However, it was lower than the Northwest Pacific (80-375 cm TL) [45].…”

Reproductive biology and diet composition of Rhynchobatus laevis (Bloch and Schneider, 1801) (Rhinopristiformes:Rhinidae) from the northern Indian Ocean

“…In conclusion, elasmobranchs, including shark-like batoids have low resilience to overexploitation by fisheries because of their atypical life history traits including late attainment of maturity, low fecundity and natural mortality, slow growth, long life spans and the close relationship between the number of young ones produced and the size of breeding biomass (Stevens et al, 2000;Varghese et al, 2016). The restricted coastal habitat, limited life history characteristics, susceptibility to capture in multiple gears and ever growing demand place coastal rhynchobatids amongst the most vulnerable chondrichthyan fishes (Dudley and Cavanagh, 2006).…”

Biological observations on the broadfin shark Lamiopsis temminckii (Carcharhiniformes: Carcharhinidae)

“…Understanding the life‐history traits and habitat characteristics are highly important in ensuring sustainable fisheries and informing management decisions. The life‐history patterns of chondrichthyans of Indian waters are poorly understood (Akhilesh et al ., ; Kizhakudan et al ., ), but recently there have been concentrated efforts to fill this knowledge gap (Raje et al ., ; Varghese et al ., ) and more regulatory (conservation and trade) implications in the region ( e.g . finning ban and fin attached policy, fin export ban).…”