Status of elasmobranchs fishery in Chennai, India

Catches of elasmobranchs in India showed an increasing trend from 27.4 thousand t in 1961 to 49 thousand t in 2006. During 2006, among the total elasmobranch catches throughout India, Tamil Nadu contributed substantially with 10.8 thousand tonnes. Observations on elasmobranchs fishery in Chennai for a period of 5 years from 2002–2006 was carried out. In Chennai fisheries harbor, annual elasmobranch catches varied from 489 t to 1735 t for the trawlnets and 194 t to 519 t for mechanized gillnets. In the same harbor, maximum catch of 2074 t of elasmobranchs was recorded in 2002. The contribution of elasmobranch i.e. 4.0 %, 16.0 % & 2.0 % to the trawl, gillnet, and hooks and line (H&L), respectively, with the CPUE of 24.4, 136.7, and 1.3 kg in the respective gears were observed. Trawlers landed heavy catch of more than 100 t of elasmobranchs during June and July with the catch per hour (cph) of 1.4–1.6 kg. Gillnet catches were better during June-September, where monthly catch was above 35 t with CPUE of 203-287 kg. H&L landed good catch during February and March, where the catch was above 1 t with the CPUE of 3.3-4.0 kg. Catch using trawlnets was dominated by sting rays (74.1%), whereas Carcharhinid sharks (51.1%) were dominant in the catch by mechanized gillnet. The elasmobranchs fishery in Chennai constituted 13 species of sharks, 13 species of rays, and 4 species of guitar fishes. Hammer head shark, Sphyrna lewini (S. lewini), was dominant among the sharks, with 33.8%, 35.0%, and 37.5% contribution in the trawlnet, mechanized gillnets, and H&L catches respectively, followed by C.sorrah and the bull shark Carcharhinus leucas (C.leucas). Among the rays, the contribution of stingray D. jenkinsii to the catch was 38.7% using the trawlnets, 31.5% using the gillnet, and 57.8% using the H&L, followed by the lesser devil ray Mobula diabolus (M. diabolus). Of the four species of guitarfishes, Rhynchobatus djeddensis was dominant. The range of size recorded for D. jenkinsii in the trawl catch was 150-1199 mm, whereas the range was from 950 to 2599 mm for S. lewini in the gillnet catch. A change in the pattern of fishery was observed during the study period. From 2003 onwards, decrease in the catch of devil ray M. diabolus (27.1-148.0 t) was observed. Increase in the catch of bull shark C. Leucas (5.1–105.4 t) and thresher shark Alopias vulpinus (0.9-28.9 t) and decrease in the catch of milkshark Rhizoprionodon acutus and spadenose shark Scoliodon laticatus were also recorded. The price structure and export markets of various by-products are given.