The study was undertaken to document the elasmobranch diversity and their abundance along Wadge Bank. Species were collected fortnightly during June 2015 to May 2016 from three landing centres viz., Chinnamuttom,Colachel and Vizhinjam of Wadge Bank. A total of 1,575 specimens were collected during the period and 44 species were identified belonging to 8 orders, 13 families and 25 genera. Among the recorded \families,Carcharhinidae is the most dominant family with 12 species. The Colachel landing centre was rich in diversity with 43 species followed by Chinnamuttom 39 species and Vizhinjam26 species. The highest Shannon Weiner diversity (H’ value) was observed at Colachel (4.17) followed by Chinnamuttom (4.11) and Vizhinjam (3.76). The Margalef’s species richness (‘d’) value was assessed at Colachel (4.55) followed by Chinnamuttom (4.01) and Vizhinjam (2.91). The Pielou’s evenness (J’) estimated was 0.7786, 0.7700 and 0.8005respectively, for Chinnamuttom, Colachal and Vizhinjam. The highest taxonomic diversity value was observed at Colachel (60.33) and the lowest during at Vizhinjam (54.08). Among the three landing centres studied, the total phylogenetic diversity (sPhi+) was found to be the lowest at Vizhinjam (940) and highest at Colachel landing centre (1720). Bray Curtis similarities measure was also calculated, fish communities were separated into several clusters based on seasons. The conservation of elasmobranchs and the management measures to be followed along the Wadge Bank is also discussed.
This study reports the length‐weight relationships (LWR) for eight elasmobranch species; four shark species (Carcharhiniformes and Orectolobiformes), two species of rays (Myliobatiformes) and two species of guitarfishes (Rhinopristiformes) from the Coromandel Coast of Tamil Nadu, Eastern Indian Ocean. The specimens of these elasmobranch species were collected from the catches of various gears like trawl net, bottom set and drift gill net, hook & line at Chennai—Royapuram Fishing Harbour, Cuddalore Fishing Harbourand Nagapattinam Fishing Harbour situated along this coastal region fortnightly during June 2019–March 2020. The values of the parameter ‘b’ remained within the expected range of 2.5–3.5. Length‐ weight / Disc‐width‐weight relationships showed good fit with r2 values varying from 0.8923 to 0.9869. This study also reports a new maximum TL length (Lmax)for a shark species (Chiloscyllium griseum).
Background: Elasmobranch is one of the largest marine fish resources, consisting of sharks, sawfishes, rays and skates. A worldwide estimate of elasmobranch diversity reveals 815 species coming under 9 orders, 42 families and 164 genera, of which 359 species are sharks and 456 are skates and rays. Hence, it has been planned to investigate the biodiversity and fishery of elasmobranchs along the Coromandel Coast of Tamil Nadu, Southeast India.
Methods: Elasmobranch specimens were collected during June 2019 to March 2020 from three main landing centres of Coromandel Coast of Tamil Nadu viz Royapuram (Chennai), Cuddalore and Nagapattinam Fishing Harbours. Sampling was done fortnightly in the above three landing centres. The specimens were collected from the catches of trawl nets, bottom set gillnets and hook and lines. The specimens were identified morphologically in the landing centres itself based on the valid taxonomic keys.
Result: In the present study, 67 species of elasmobranch belonging to 7 orders, 21 families and 46 genera were recorded. Of the 7 orders, Carcharhiniformes had the largest number of species (27). Among the 25 families, Carcharhinidae (21) had the largest representation.
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