359 research outputs found
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 = тАФ4.8378 + 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= тАФ 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
- тАж