Journal of the Marine Biological Association of India

Biology and fishery of silky shark (Carcharhinus falciformis) of Negombo, Sri Lanka

Volume 65 Issue 2

H. M. S. G. Karunanayaka and H. A. C. C. Perera

10.6024/jmbai.2023.65.2.2373-12

Abstract

A total of 208 silky sharks, which were collected by single-day and multi-day boats using gillnets and longlines, were gathered from the Negombo fishing harbour, Sri Lanka, from August to December 2020 to study their biological parameters. The total length range of the silky sharks was 39.0-285.0 cm, while their weight range was 3.5- 75.0 kg. The length-weight relationship was obtained for males and 55 females, and the pooled samples were W = 0.0957 TL1.0644, W = 0.0346 TL 1.2769, and W = 0.0557 TL 1.,1781 and the ‘b’ values were 1.0651, 1.2776 and 1.1788 respectively. All the ‘b’ values were significantly different from 3 (P <0.05) and showed negative allometric growth. One hundred fifty-three 153 males were examined as immature, maturing and mature. Of that, the highest percentage of male silky sharks were immature (39%) than the maturing (27%) and mature stages (33%). Stomach contents were fish remains (84.21%), arthropod remains (15.79%) and molluscan remains (5.26%). Among the 48 fishing vessels observed, there were singleday boats (27.1%) and multi-day boats (72.9%). Of 98 silky sharks, 77.6% were caught by multi-day boats while 22.4% were by singleday boats. And longlines accounted for capturing a higher percentage of silky sharks (61.2%) than gillnets (38.8%). The identified other by-catch species caught by the boats during the study were sharks, billfishes and rays. The silky shark is considered the dominant shark species in the total shark landing in Sri Lanka. Due to the K-selected life histories of sharks, silky shark populations are also vulnerable to overexploitation. Therefore, having sound knowledge of the biology of silky sharks is helpful for the conservation and management of them.

Keywords

Negative allometric growth, Negombo, silky shark, stomach content

Date : 14-11-2023