Changes in the biochemical and mineral composition of hilsa shad, Tenualosa ilisha (hamilton, 1822) during upstream spawning migration.

Abstract

A study was conducted to examine the changes in biochemical composition consisting moisture, protein, lipid, carbohydrate, ash content and mineral composition of Indian shad, hilsa (T. ilisha) during upstream migration for spawning from off-shore of the Bay of Bengal to the Bhagirathi-Hooghly zones of the Ganga river system in India. Adult hilsa fish were collected from seawater (SW), freshwater 1 (FW1) and freshwater 2 (FW2) locations, where the salinity level was 26-28‰, 1-5‰ and 0-0.04‰ respectively. The moisture and carbohydrate varied significantly among three locations, but not the protein and ash contents. The moisture content of hilsa collected from different habitats ranged between 62.40% and 68.71%, whereas, the protein, lipid, carbohydrate and ash percentages were 15.22%, 12.61%, 0.84%, 2.59% and 15.59%, 14.35%, 3.85%, 3.78% in seawater and freshwater respectively. The minerals like sodium, potassium and calcium were highest in SW hilsa compared to FW hilsa. However, iron content was highest in FW hilsa compared to SW hilsa. The results indicate that the migration influences the nutritive value of hilsa, as the lipid, sodium, potassium and calcium levels significantly reduced during upstream river migration. It further, point out that the lipid and carbohydrate mobilized as the energy source to support long migration and gonadal development. The ionic profile of hilsa muscle showed location effects, and the values declined while the fish migrated through freshwater indicates that the energy driven metabolic processes might govern the acclimation of upstream migration and spawning of T. ilisha.