Artificial spawning by stripping in Dussumieria acuta, a marine pelagic fish and studies on its early development

Artificial spawning was successfully conducted in Dussumieria acuta Valenciennes (Family: Dussumieriidae), a marine pelagic fish, by stripping the fully ripe female and male. The experiment was conducted on board a privately owned shrimp trawler operated in the Palk Bay, by participating in one of its night fishing trips, on 2nd March, 1973. The stripped eggs and milt were mixed in filtered sea water. Majority of the eggs were fertilized. Detailed microscopic studies were conducted the next day in the laboratory. The first larva hatched out 24 hours after fertilization. The larvae could be reared only upto 48 hours after hatching. The developmental stages of the embryo and the larva are described and discussed. It is suggested that the technique of artificial spawning by stripping and early ranching of the embryos into the sea, if arried out by the fishermen in a variety of commercially important species which it is possible on board the fishing vessels on a large scale, can increse the natural production

विषिंजम की करंजिड मात्स्यिकी

कृपया पूरा लेखा पढ

Carangid resources of India

A review of the research work carried out so far on various aspects of the carangid resources has been made in this paper based mainly on the published contributions of Central Marine Fisheries research Institute. The fluctuations in the fishery since 1950 and its present status, in the light of the improved tackling devices and changed fishing patterns, have been analysed. A drastic increase in the landings was noticed since 1985 which was mainly due to the mechanization of the country crafts, the use of purse seine and ringseine, intensification of trawling and the introduction of multiday fishing. The studies on the food and feeding habits have revealed that almost all species of carangids are pelagic carnivores, feeding mainly on a variety of smaller crustaceans and fishes. The stock assessment studies conducted on certain commercially important species have shown that most of them are either optimally or under-exploited and hence there is scope for increasing the production without adverse effect on the sustainability of the stocks

On the occurrence of the soft-shelled turtle, Pelochelys bibroni (Owen) in marine environment

A soft-shelled turtle, Pelochelys bibroni (Owen), caught alive from Palk Bay — a new record from the sourther part of lndian peninsula — proves beyond doubt that the species can tolerate the marine environment, as against the belief that it is purely a freshwater form. The behaviour of the animal was studied keeping it under captivity for 14 days

Mixed farming or polyculture

In Kerala, nearly 75-80% of the population consume fish and their annual per capita consumption rate is about 13 kg. The rate of fish consumption is likely to go up due to increased awareness about fish as a source of cheap and highly nutritious but harmless food item. Hence there is every need to augment fish production not only to meet our food requirements but also to increase foreign exchange earnings. The current level of fish production is inadequate to fulfil all these needs. An analysis of the trend of fish production during the past few years indicates that there may not be any significant improvement in it in the coming years. In this context, measures to increase fish production are to be thought of Aquaculture is the only way to achieve this. In Kerala at present aquaculture is restricted to backwaters and inland waterbodies. In order to enhance fish production, farming of fish and other species of aquatic organisms is to be extended to inshore coastal waters for which suitable farming methods are to be adopted

The resources of the Indian mackerel - characteristics, exploitation and future prospects

The Indian mackerel contributed to an annual average (1993-'99) catch of 2.17 lakh tonnes (t). The west coast landed about 80% of its total catch and remaining by the east coast. The resource is rich in upwelling areas of the west coast with a catch contribution of 38.68% from Kerala followed by Kamataka and Maharashtra. The fishery is characterized by annual fluctuations in the catch ranging from 0.14 lakh t in 1968 to 2.9 lakh t in 1989. The annual fluctuations do not show any pattern; whereas the decade! trends show a cyclic pattern of ups and downs. The fluctuations are more pronounced along the upwelling areas of the west coast. In 1990s, there was a quantum leap in the annual catch chiefly due to the introduction of large seine nets and motorization of country crafts. The increase was maximum in Kerala, moderate in Maharashtra and poor in Kamataka. Along the east coast also fishery showed considerable improvement. Of late, the role of trawl net in the mackerel fishery is gaining importance. The surface fishery using large seines along the upwelling areas seems to depend very much on the intensity and duration of upwelling which is perhaps causing the fluctuations in catch rather than the variations in the abundance of the resource. The behaviour of the fish to ascend with upwelling and spreading to deeper waters with sitiking of thermocline seem to control exploitation and protect the resilience of the stocks. Perhaps the richness of the resource is much stronger than hitherto believed. With proper management the production can reach further heights

സമ്മിശ്ര മത്സ്യകൃഷി (Mixed farming or Polyculture)

The rate of fish consumption is likely to go up due to increased awareness about fish as a source of cheap and highly nutritious but harmless food item. Hence there is every need to augment fish production not only to meet our food requirements but also to increase foreign exchange earnings. The current level of fish production is inadequate to fulfil all these needs. An analysis of the trend of fish production during the past few years indicates that there may not be any significant improvement in it in the coming years. In this context, measures to increase fish production are to be thought of Aquaculture is the only way to achieve this. In Kerala at present aquaculture is restricted to backwaters and inland waterbodies. In order to enhance fish production, farming of fish and other species of aquatic organisms is to be extended to inshore coastal waters for which suitable farming methods are to be adopted

The status of carangid fishery at Vizhinjam, Trivandrum coast during 1979-'88

The status of carangid fishery at Vizhinjam during the decade 1979-'88 is evaluated. The details of fishing crafts and gears,catch composition, annual trends are given

On the systematics of rainbow sardines Dussumieria spp. (Family: Dussumieriidae, Pisces) from indian waters

The systematics of the rainbow sardines of the Genus Dussumieria Valenciennes has been studied in detail. The existence of two species namely Dussumieria acuta Valenciennes and D. hasseltiiJlleeker in Indian waters has been re-established as against the view of Whitehead (1963) who synonymised these two species to one namely D. acuta Val. In this study specimens collected from east and west coasts of India were analysed morphometrically and meristically and the characters compared statistically. Clear differences in many of the characters, sufficient enough to substantiate the existence of two different species, were noticed. The two species are redescribed and photographs presented in the text

The age and growth rate of rainbow sardine Dussumieria acuta from Mandapam area and its age group composition in the fishery

The age and growth rate of Dussumieria acuta of the Gulf of Mannar and the Palk Bay, during April 1969 to March 1971 was studied. According to the Peterson's method of length frequency analysis the fish grows to a total length of73 mm, 95.5mm andll3 mm at the endoflst, 2nd and 3rd quarters of an year and to 128 mm at the end of 1st year, resulting an average growth rate of 10.75 mm per month. Results of the Probability Plot technique of Cassie (1954) applied to the data, showed perfect agreement with those of Peterson's method. Von Berfalanffy's growth equation was fitted and the estimated values of the growth parameters were: Loo = 191 mm, K = 0.20701 and to = -1.34 quarters. Theoretically the fish grows to a length of 128.05 mm, 163.28 mm and 178.91 mm at the end of 1st, 2nd and 3rd years. No growth rings were traceable on the otoliths, but a straightline relationship could be noticed between the lengths of otolith and the fish. The growth by weight showed that the optimum age for exploitation of D. acuta is when the fish is 1 to 11 years old. A study of the age composition of D. acuta in the commercial catches during 1969-71 showed that in the shore seine and the gill net catches 1-year group dominated, whereas in the trawl net catch the O-year class dominated during 1969-70 and 1-year class during 1970-71