Further observations on the biology of the sting ray, Dasyatis imbricatus (Schneider) at PortoNovo

The length weight relationship of Dasyatis imbricatus (schneider) was calculated separately for males and females. The results show that exponent is greater than 3 for females suggest ing that growth is not strictly isometric. Analysis of gut contents reveal the bottom feeding nature of this ray with crustacean forms constiluting 64.8% followed by polychaetes with 33.5 of the feed. The size at first maturity is determined by relating the percentage of liver weight in body weight to the average body weight and also to the length of the body

On some specimens of abnormal elasmobranchs

Instances of deformities or abnormalities have been reported on and off in fishes. The abnormality is extreme in certain cases that it is very difficult even to identify them correctly and this leads to creation of new taxa

Shark fishing in India

From time immemorial sharks have been the object of amusement for the sea faring men and anglers and they were fished for sports. At certain times of history they were dreaded as monsters of the sea because of the ravage they wrought on bathers, fishermen and their boats. Even the very appearance of an heavily built creature with open mouth full of sharp and ferocious teeth and black fins gives a fearsome apparition to unarmed people taking bath ill the shallow waters. Of all the 350 species of sharks inhabiting the seas of the globe, only less than 35 species are aggressive and attack human beings, boats and other objects. While it is true that there are a few ana,cks sporadically on human beings throughout the world, recent findings have shown that one , is less likely to be attacked by a shark than having a serious accident at bome or in the roads. One should give a wide berth to larger sharks considering their size and speed of action. Even a slight contact with their abrasive skin may resnlt in severe lacerations and damage will be irreparable. One should also avoid bathing in sea with fresh wounds especially when sharks are around

A brief description of the cat shark, Chiloscyllwm griseum Muller and henle, from Indian waters, with some biological notes

The cat shark, Chfloscyllium griseum, is described in detail based on samples collected frcm both the coasts of India. The patterns of growth of individual organs are also given. The length-weight relationship was not significantly different between sexes, so a common value, Log W = —4.8378 + 2.7314 log L, was obtained. The shnrk feeds on bottom fishes. Males mature at 520 mm and females at 530 mm TL. The egg-cases are laid outside for development

Sex change in hound shark, along Madras coast

The big eye hound shark, logo omanensis has been recorded from the continental shelf off Bombay and Kutch region along the west coast and the Gulf of Mannar in the east coast

On a Smooth Hammerhead Shark, Sphyrna zygaena (Linnaeus. J 758) New to Indian Waters

A mature female smooth hammerhead shark, Sphyma zygael1a ( Linnaeus), 2 .14 cm TL (T<lbJe I). was collected on 6- 10-1975 from the hook and line fishing operated from the mechanised vessels off Porto Novo at a depth of 80-90 meters. Since hammerheads are ident ified from the shape of head and teeth s truCtures only, the head has been preserved in the museum of the Marine Resea rch Laboratory of Annamalai University, Porto Novo

Studies on the catshark Chiloscyllium griseum from Indian waters

The catshark Chiloscyllium griseum belonging to the family Hemiscyllidae is described in detail from samples collected from both east and west coast of India. Various patterns of growth of individual organs are described. Analysis of data on length-weight relationship showed no significant difference between sexes. Hence a common value of Log W= — 4.8378 + 2.7314 log L is obtained. The shark feeds on bottom fishes and crustaceans. Males mature at 520 mm and females at 530 mm total length. The paired oviduct contains 4 egg-cases, 2 on either side at a time without any embryonic development taking place while inside the oviduct. The egg-cases are laid outside for embryonic development and hatching in the sea water

A new record of fantail ray Taeniura melanospila (Bleeker, 1853)

Four fantail ray Taeniura melanospila (Bleeker 1853) measuring between 950 mm and 1800 mm across the disc were recorded at Madras for the first time from the coastal waters of the Indian subcontinent. A detailed description of the ray and morphometric measurements are given in the text

Maturity and spawning in Otolithus ruber (Schn.) and Johnlos dussumierl(C. & V.)

From the ova diameter measurements, it has been observed that O. ruber spawns only once a year during July to October, and /. dussumieri spawns twice a year, first between January and February and again between June and September. Indication of sexual maturity is observed in the 170 mm size group in O. rafieranda majority (62.86%) is mature at 200 mm. In /. dussumieri sexual maturity is manifest in the 140 mm size group and a majority offish (51.85%) is mature at 160 mm. Fecundity in the size range of 180-290 mm varies between 44,621 and 179,659 mature eggs in O. ruber, and in /. dussumieri of size range 195-235 mm the number of mature eggs varies between 142,005 and 225,988

On the incidental fishery of skates and rays off Calicut

The total skates and rays landed as incidental components by the three main gears, trawl net, drift net and hooks-and-lines, accounted for 70.9 t, forming 10% of the total elasmobranch landings of Calicut during 1977-80. The most common species of rays were the sting rays, spotted eagle-ray, and the devil-ray, and the skate, R. djeddensis. The trawlers alone landed 95%. The trends of effort, catch and catch rate, examined for the 10-year period 1971-1980, showed that during the earlier half both catch and CPUE had a general upward trend, the former reaching the alltime high of 64 t in 1974 followed by the latter reaching the maximum of 11.9 kg per standard effort in 1975, after which both had descended down steadily to the alltime low of 1980, with clear negative response to effort, indicating the probability that the stock in the area could not stand the type of effort that was put in 1974-75. The reasons peculiar to this elasmobranch group contributing to its easy depletion are pointed out