Proteins and amino acids are important biomolecules which regulate key metabolic pathways and serve as precursors for synthesis of biologically important substances; moreover, amino acids are building blocks of proteins. Fish is an important dietary source of quality animal proteins and amino acids and play important role in human nutrition. In the present investigation, crude protein content and amino acid compositions of important food fishes from different habitats have been studied. Crude protein content was determined by Kjeldahl method and amino acid composition was analyzed by high performance liquid chromatography and information on 27 food fishes was generated. The analysis showed that the cold water species are rich in lysine and aspartic acid, marine fishes in leucine, small indigenous fishes in histidine, and the carps and catfishes in glutamic acid and glycine. The enriched nutrition knowledge base would enhance the utility of fish as a source of quality animal proteins and amino acids and aid in their inclusion in dietary counseling and patient guidance for specific nutritional needs.

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Aquaculture is emerging as one of the most viable and promising enterprises for keeping pace with the surging need for animal protein, providing nutritional and food security to humans, particularly those residing in regions where livestock is relatively scarce. With every step toward intensification of aquaculture practices, there is an increase in the stress level in the animal as well as the environment. Hence, disease outbreak is being increasingly recognized as one of the most important constraints to aquaculture production in many countries, including India. Conventionally, the disease control in aquaculture has relied on the use of chemical compounds and antibiotics. The development of non-antibiotic and environmentally friendly agents is one of the key factors for health management in aquaculture. Consequently, with the emerging need for environmentally friendly aquaculture, the use of alternatives to antibiotic growth promoters in fish nutrition is now widely accepted. In recent years, probiotics have taken center stage and are being used as an unconventional approach that has numerous beneficial effects in fish and shellfish culture: improved activity of gastrointestinal microbiota and enhanced immune status, disease resistance, survival, feed utilization and growth performance. As natural products, probiotics have much potential to increase the efficiency and sustainability of aquaculture production. Therefore, comprehensive research to fully characterize the intestinal microbiota of prominent fish species, mechanisms of action of probiotics and their effects on the intestinal ecosystem, immunity, fish health and performance is reasonable. This review highlights the classifications and applications of probiotics in aquaculture. The review also summarizes the advancement and research highlights of the probiotic status and mode of action, which are of great significance from an ecofriendly, sustainable, intensive aquaculture point of view.

The Ganges River is one of the largest river systems in the world and sustains a rich biodiversity of fish and fishers. In recent years, a decline in fish diversity and catch has become apparent due to various anthropogenic activities in the river basin. This study analyses the current fish diversity, distribution and community structure along the longitudinal gradient of the river and evaluates the ecological integrity of the riverine stretch applying a multimetric assessment approach. One hundred forty three fish species were recorded from the river and Cyprinidae was the dominant family. The middle stretch of the river exhibited dominance of small bodied erytopic, indigenous and exotic fish species with periodic and opportunistic life history strategies with significant decline of the large bodied prized Indian major carps. A tropic shift towards dominance of carnivore catfish species is evident. Non-metric multidimensional scaling revealed greater distribution and abundance of fish species with increasing river width and depth, higher sediment organic carbon, silt and clay along the river gradient. A significant change in the catches composition was evident from 1961 to 2010 in the middle stretch of the river at Allahabad. It reflected a progressive decline in proportion of Indian major carps (IMC) and the anadromous Shad Tenualosa ilisha and a significant increase in the proportion of exotic fish Cyprinus carpio and Oreochromis niloticus which represented 43–48% of the total catch. Assessment of biotic integrity showed that 28% of sample locations in the river supported fish assemblages under acceptable conditions.

Changes in hsp gene expression profiles in murrel Channa striatus experimentally exposed to temperature stress (36°C) for 4, 15, and 30 days were investigated; fish collected from aquaculture ponds and maintained in laboratory at the pond temperature (25 ± 1°C) served as control. Channa collected from a hot spring runoff (36°C) was included in the study to examine the hsp profiles beyond 30 days of exposure. Gene expression analyses of a battery of hsps in liver tissues were carried out by quantitative RT-PCR and protein expressions were analyzed by immunoblotting. hsps could be grouped into three clusters based on similarity in response to heat stress: hsp70, hsp78, and hsp60, whose transcript level continued to increase with duration of exposure; hsp90 and hsp110 that increased to a much higher level and then decreased; hsp27 and hsp47 that did not significantly vary as compared to control. The results suggest that Hsp70, Hsp78, and Hsp60 are involved in thermal acclimation and long term survival at high temperature. Fish living in the hot spring runoff appears to continuously express hsps that can be approximated by long term induction of hsps in farmed fish if temperature of their environment is raised to 36°C.

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The Hilsa shad, Tenualosa ilisha popularly known as ‘Hilsa’, is one of the most commercially important fish species in South Asian countries. The species is widely distributed from the Persian Gulf to Bay of Bengal and ascends into estuaries, rivers and brackish‐water lagoons of the Indo‐Pacific region. Recently, the availability of hilsa has drastically dwindled in aquatic systems across this region, due to anthropogenic pressures, mainly intensive fishing and river obstruction by dams and barrages. Climate change may also be contributing to the declining populations. Hence, there is an urgent need for conservation of the species. In addition, hilsa is of great cultural and economic importance among the peoples of Ganga‐Brahmaputra‐Meghna basin, with very high market demand and increasingly high prices, presently an average of around US$ 12 per kg for consumers both in India and Bangladesh. Many attempts at hilsa breeding and culture have been made across South Asia, particularly in India and Bangladesh, since the 1900s. To date, no breakthrough has been achieved in completing the life cycle in captivity. This review provides an insight into the status of artificial breeding, larval rearing and culture of this species, and identifies research gaps that need to be addressed by future aquaculture development programmes for hilsa in South Asia.

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