Biochemical changes in the body components during gonad maturation of the tropical abalone Haliotis varia were investigated using wild collected specimens from the Gulf of Mannar, on the southeast coast of India. The gonadosomatic index (GSI) and the hepatosomatic index (HSI) showed negative correlations throughout the study period as well as during the progression of gonad maturation stages. The highest GSI for both the sexes were in the ripe stages followed by late maturing stages. The HSI ranged from 2.97 to 6.71 in females, and 3.55 to 5.09 in males. Among the biochemical components analysed, lipid and carbohydrate contents showed significant variations in the different tissues of H. varia during the progress of gonad maturation. The highest protein content was in the foot muscle and the lowest was in the digestive gland. Total lipids in the ovary were always higher compared with that of the testis and the values ranged from 12.60 to 26.49%, registering the highest value in the ripe ovary. Gonad carbohydrate content was lower when the lipid content was higher, suggesting the conversion of carbohydrate to lipids. The present study demonstrates the role of nutrient translocation between body parts as an essential part of the reproductive physiology of abalone.

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Spawning, larval and juvenile rearing of the tropical abalone Haliotis varia L. were studied. Brood stock abalone were induced to spawn by exposure to air for 2 h at 27 jC. Female abalone spawned a mean of 76,530 eggs. Fertilised eggs measured 180 Am in diameter. Seventy percent survival was obtained during larval rearing. Larvae passed trochophore, veliger, gliding and creeping stages and were induced to settle on a mat of diatoms containing Nitszchia sp. and Navicula sp. The larval rearing period of H. varia ranged from 4 to 6 days at 27 jC. The settled spat vigorously fed on the diatom mat until the 50th day of postfertilisation and coralline red algal film, until the 70th day of postfertilisation. First respiratory pore was formed on the 27th day of postfertilisation. Juvenile abalones were reared on three algal diets such as coralline red algae, green filamentous algae and Ulva lactuca from the 71st to 200th day of postfertilisation. Those fed with coralline algae showed best and consistent growth. Shell colour of juveniles was affected by diet. The present study on the production of juveniles in the hatchery is a baseline information to initiate abalone aquaculture in India and to help augment the natural population. D

Ultrastructural features of the ovary as well as oogenesis were examined in the variable abalone Haliotis varia with the help of transmission electron microscopy. Based on the ultrastructure, the female germ cells were divided into 5 stages; oogonia, pre-vitellogenic, early vitellogenic, late vitellogenic and mature oocytes. Oogonia were supported by follicle cells that lined up the inner walls of the ovary. Vitellogenesis in H. varia commenced at about 50 µm oocyte diameter, with a major contribution by the autosynthetic pathway. Lipid droplets and protein yolk granules, measuring 2.3 ± 0.2 and 2.5 ± 0.3 µm, respectively, were observed in late vitellogenic and mature oocytes. Vitellogenic oocytes were encircled by a vitelline envelope consisting of a single layer of about 2.3 µm thickness. Numerous microvilli were embedded in the vitelline envelope. Cytoplasmic inclusions such as cortical granules, lipid droplets, mitochondria and yolk granules constituted the fundamental components of the mature oocyte. The cortical granules were arranged beneath the oolemma at the cortex of the oocyte. Oocyte degeneration in H. varia was observed in all stages of oocyte development, except in oogonial cells and pre-vitellogenic oocytes.

Apart from penaeid shrimp culture, crab farming and fattening and other several diversified aquaculture practices are now emerging as viable ventures in India. About 11 types of crab products are being exported from India with an average unit value realization of US$ 3.73 kg -1 , pinpointing its importance in the foreign exchange earnings. An economic evaluation of mud crab culture, fattening and fattening with composite culture of shrimp/finfish has been attempted in this paper. The major operating cost was that of seed and it was higher for crab fattening (87% of the total operating cost). Feed costs were very low compared to that of shrimp farming. Annual profit obtained was US$ 22812.5 ha -1 year -1 for culture and US$ 30820.8 ha -1 year -1 for fattening. Economic indicators such as net profit, rate of return, pay back period and breakeven price indicate that crab fattening/culture is much more profitable than any other coastal aquaculture operations currently in practice, provided hatchery production is established in the country to ensure adequate supply of mud crab seeds.

A biomass dynamics modelling study to derive biological reference points and management requirements of 223 commercially important fish stocks in different maritime states of India was conducted. Two decades (1997–2016) of fishery-related data on the harvest of resources by different types of fishing fleets formed the input. The multigear nature of the fishery situation was solved by introducing a gear standardization parameter into the biomass dynamics model. The relative positions of the fish stocks were depicted through Kobe plots generated for the ten maritime states/union territory, and the fish stocks were categorized, based on the status, into sustainable, overfished, recovering, and overfishing. The results indicate that 34.1% of the assessed fish stocks in the country are sustainable, 36.3% are overfished, 26.5% are recovering, and 3.1% are in the overfishing status. Regionally, the percentage of sustainable fish stocks were high along the southwest coast (51.6%), overfished stocks were high along the northwest coast (54.2%), and recovering fish stocks were high along the northeast coast (47.8%). The national mean B/BMSY was estimated as 0.86, which is a strong reason for strengthening fisheries management. Fishing fleets harvesting overfished stocks were examined for each maritime state, and recommendations regarding reduction in annual fishing hours are made.

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