DNA barcoding was successfully used for the accurate identification of chondrichthyans in the Indian commercial marine fishery. About 528 specimens of 111 chondrichthyan species and 34 families, collected from the Indian EEZ, were barcoded for a 655 bp region of the mitochondrial gene cytochrome c oxidase subunit 1 (COI). Generally, five specimens per species were barcoded, but numbers ranged from 2 to 13. The average Kimura 2 parameter (K2P) distance separating individuals within species was 0.32%, and the average distance separating species within genera was 6.73%. Ten species were suggested as putative new species requiring formal descriptions. Based on the morphology and molecular support, 11 elasmobranch species were confirmed first records for Indian waters. The present study confirms the ability of DNA barcoding for the accurate identification of sharks, rays, and their products from Indian waters.
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Fishery and biological data are presented for the poorly known bramble shark Echinorhinus brucus (Squaliformes: Echinorhinidae), from the deep waters of the south-eastern Arabian Sea. A total of 5318 individuals from by-catch landings of deep-water bottom set longlines, gillnets and shrimp trawl fisheries operating at depths of 200-1200 m were recorded between January 2008 and December 2011 at the Kochi Fisheries Harbour (Kerala). A total of 431 individuals, from 46 to 318 cm total length (L(T)) and 0·8 to 132 kg total mass (M(T)), were examined to determine biological data for this species. The LT at which 50% were mature (L(T)50) for females and males was estimated at 189 and 187 cm LT. Litter size ranged from 10 to 36 and size at birth was between 42 and 46 cm L(T). Dietary analysis of stomach contents revealed E. brucus feeds on a variety of prey including crustaceans (69% index of relative importance, I(RI)), teleosts (25·8% I(RI)), cephalopods (1·7% I(RI)) and elasmobranchs (0·7% I(RI)). This study provides the first detailed biological data for this species and also highlights the extent of the by-catch fishery for this species in Indian waters.
Biological data are presented for the poorly known bristly catshark Bythaelurus hispidus based on specimens collected from the by-catch of the commercial deep-sea shrimp trawl fishery operating in the Arabian Sea at depths of 200-500 m off the south-west coast of India. One hundred and sixty-two individuals, which ranged from 120 to 366 mm total length (L(T)), were collected for this study. Size-at-maturity (L₅₀) for females and males was estimated at 252 and 235 mm L(T), respectively. The reproductive mode of B. hispidus was aplacental viviparity, which is the rarest reproductive mode within the Scyliorhinidae and is considered to be the most advanced of the three reproductive modes occurring within this family. Dietary analysis of stomach contents revealed B. hispidus feeds on a variety of prey, primarily fishes.
Cd, 18.7 µg g −1 ; and Pb, 6.55 µg g −1 ) were found to be higher of comparable magnitudes than the Arabian Sea zooplankton (Fe, 1786 µg g −1 ; Co, 14.2 µg g −1 ; Ni, 18.6 µg g −1 ; Cu, 21.5 µg g −1 ; Zn, 374 µg g −1 ; Cd, 16.5 µg g −1 ; and Pb, 4.0 µg g −1 ). The spatial variability of metal contents in zooplankton from both basins indicates that it is markedly enriched in coastal samples than offshore samples. The metal enrichment in zooplankton from the coastal areas of the eastern Arabian Sea occurs due to a combined effect of upwelling, riverine, and anthropogenic sources, whereas the latter two are only dominating in the coastal Bay of Bengal zooplankton. A comparison of average trace metal concentrations in the zooplankton from the Arabian Sea and Bay of Bengal showed that the enrichment of Fe, Zn, Cd, Ni, Cu, and Pb in the Bay of Bengal zooplankton may be due to high bioaccumulation factor of these elements, whereas the slight Co enrichment may be due to the bioavailability of this metal in the seawater.
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