Knowledge of the changes of essential nutritional constituents (i.e. moisture, protein, lipid, minerals, amino acid and fatty acid profile) of fish with seasons is indispensable to estimate their energy value and to plan the most appropriate industrial and commercial processing. This article critically reviewed the nutritional constituents of 28 different fish species of Bangladesh and other South Asian countries like India, Pakistan in three different seasons viz. pre monsoon (April-June), monsoon (August-October) and post monsoon (December-February). Available findings have shown that proximate composition, amino acid and fatty acid profile varied in accordance to changes of the seasons. As the environmental factors including water temperature, pH, salinity and food availability changes with the seasons, which in turn influence the amino acid and fatty acid profile of fish in different season. Moisture content known to vary in some fishes for maintaining osmoregulation during migration. This phenomenon also largely affects the seasonal variation of proximate composition of fish. In addition, age, size, sex, habitat, breeding season and starvation during migration are also known to diverge the nutritional composition of fish in different seasons. It is generally view that fish utilizes lipid as energy source in different seasonal circumstances as gonadal development, maturation, spawning or migration and there is an inverse relationship between lipid and moisture content. Protein, lipid, amino acids and saturated fatty acid concentration were comparatively higher in pre-monsoon and lower in post-monsoon, whereas monounsaturated fatty acids and polyunsaturated fatty acids were higher in post-monsoon season in many of the fishes; attributed to gonadal development of fish, when it migrates a long way. Finally, this review might help to understand the changes in nutritional values of some commercial fishes in various seasons and will assist in identifying the proper fish harvesting period.
Key words: Proximate composition, seasonal variation, freshwater and marine fish, South Asian countries
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