Testicular development in migrant and spawning bluefin tuna (Thunnus thynnus (L.)) from the eastern Atlantic and Mediterranean

Testis histological structure was studied in bluefin tuna (Thunnus thynnus) from the eastern Atlantic and Mediterranean during the reproductive season (from late April to early June). Testicular maturation was investigated by comparing samples from bluefin tuna caught on their eastward reproductive migration off Barbate (Strait of Gibraltar area) with samples of bluefin tuna fished in spawning grounds around the Balearic Islands. Histological evaluations of cross sections showed that the testis consists of two structurally different regions, an outer proliferative region where germ cells develop synchronously in cysts, and a central region made up of a well-developed system of ducts that convey the spermatozoa produced in the proliferative region to the main sperm duct. Ultrastructural features of the different stages of the male germ cell line are very similar to those described in other teleost species. The bluefin tuna testis is of the unrestricted spermatogonial testicular type, where primary spermatogonia are present all along the germinative portion of the lobules. All stages of spermatogenesis were present in the gonad tissue of migrant and spawning bluefin tuna, although spermatids were more abundant in spawning fish. The testis size was found to increase by a factor of four (on average) during migration to the Mediterranean spawning grounds, whereas the fat bodies (mesenteric lipid stores associated with the gonads) became reduced to half their weight, and the liver mass did not change significantly with sexual maturation. Linear regression analysis of the pooled data of migrant and spawning bluefin tuna revealed a significant negative correlation between the gonad index (IG) and the fat tissue index (IF), and a weaker positive correlation between the gonad index (IG) and the liver index (IL). Our analyses indicate that the liver does not play a significant role in the storage of lipids and that mesenteric lipid reserves constitute an important energy source for gametogenesis in bluefin tuna.

Spawning behavior and larval development in Mopalia lignosa and Mopalia muscosa (Mollusca: Polyplacophora) in central California

Spawning behavior and external features of the larval development were studied in the chitons Mopalia muscosa and M. lignosa during the months of April-June, 1974, at Pacific Grove, California. ... The sequence of events in the development of the two species in the same, though some differences in timing exist.

A comparative note on the modus operandii of reservoir development in Republic of China and India

Principles adopted by China for the development of reservoir fisheries are discussed. Production of some of reservoirs of China with that of India is compared. The reasons for obtaining higher production in China have been recognised as: emphasis on utilization of all resources for food production; direct feeding; use of selected varieties of fast growing carps; keeping 15 pigs per hectare of water area for application of pig void and application of manure; production of fingerlings at the reservoir sites enclaving coves and bays; grading and removing obstructions from bottom; rational harvesting and stocking and improvement of reservoir shore areas as a whole. Some of these measures which could be implemented in Indian conditions are briefly described.

Induced breeding, embryonic and larval development in Heteropneustes fossilis (Bloch) in the agro-climatic conditions of Maharashtra

Heteropneustes fossilis was induced bred for the first time in the agro-climatic conditions of Maharashtra, India. The embryonic development was completed within 16-18h after fertilisation. Head and tail ends were distinguishable after 3h and 11-12 somites were visible after 6-7h. The eggs started hatching after 14h of incubation. Average hatching time was 16-18h at 26 degrees C. In first day old pro-larva, notochord was deflected upwards, eyes were darkly pigmented and alimentary canal appeared. In fourth day old post-larva intestinal coiling could be seen and yolk was absorbed. Aerial respiration started by 8th day. The 10 day old post-larva was free swimming and fed voraciously attaining a length of 20 mm in 30 days.

Impact of mechanisation of fisheries development in Karnataka

Karnataka, one of the maritime states on the west coast of India, has progressed quite well in marine fisheries due to its vast fisheries resources and diversification in mechanised fishing. Mechanisation programmes were started by the state from 1957-58 only. Starting with two small mechanised boats, the state has today a fishing fleet of 398 purseseiners, 731 gillnetters, 2 deepsea trawlers and about 1,500 shrimp trawlers contributing over 85% of the total marine fish landings. The marine fish production during 1987-88 up to the end of March 1988 was 1,29,659 tonnes valued at Rs.48.05 crores.

Marine fisheries development in India, 2000 AD: a perspective

The status of marine fisheries research and development in India is discussed and the need for a high power national body to coordinate these activities is stressed. Priority areas for research and development have been outlined. It has been stressed that the strategy should be to achieve a production target of 3 million tonnes on the capture fisheries front (2.5 million tonnes from the inner shelf and 0.5 million tonnes from the outer shelf and slope areas) and 1 million tonne through aquaculture by 2000 AD.

Prospects of fisheries development in India by 2000 AD

The fishery resources of India are extensive. The demand for fish for domestic consumption will be at least 10 million by 2000 AD. With proper planning and management, fish production from inland, brackishwater and marine sources can be increased to 5 million tonnes, 1 million tonne and 4 million tonnes respectively. But the increase in the last 37 years is approximately equals 2.1 million tonnes over the base level of 1950. If the present trend is continued, the expected fish production will be approximately equals 6 million tonnes by 2000 AD, and hence, only approximately equals 60% of the domestic demand can be met.

Trends in development in the prawn fishing technique in India: a review

The paper provides some background information about the developments in the prawn fishing technique. The important indigenous gear for prawns are the filtering type nets like the stake nets, boat seines and beach seines with bag. The only indigenous net, which can be compared in design with the modern bottom trawling gear, is the "Thuri Valai" of the Madras Coast. Prawns have also been reported from the catches of gill nets and cast nets. Dredges and beam trawls are simplest among the dragged gear. Even though several earlier attempts were made with the beam trawl, in 1959 season a detailed experiment was made to study the fishing features of this gear. The subsequent experiments conducted were for comparison with otter trawl, towing of 2 beam trawls one behind the other and the use of tickler chain. The initial experiments with otter trawls were mainly directed towards operational aspects. The experiments were to evaluate the effectiveness of fully mechanised and partially mechanised operation, the effect of extra buoyancy of floats and the use of tickler chain. Subsequent developments had been on the structure and design of prawn trawling gear. Effect of long wings and sweeps were tested. Catches of nylon and cotton nets were compared. The sizes of meshes of the cod-end have also been increased.