Annual variation of the biochemical composition, energy reserves and physiological indices in Mactra stultorum tissues from the Tunisian coasts

Abstract

The present study assessed the consequences of environmental changes on the biochemical quality and the physiological condition of the whole body and others organs Mactra stultorum collected from the north coast of Tunisia. Significant variations in the biochemical components, PE and CI have shown between seasons. The depletion of glycogen in all tissues was recorded during spawning periods (late spring and summer). Lipid accumulation in gonad–visceral mass during the early and late gametogenesis stages was associated with the increase in CI and GSI. However, decreases in lipid and protein contents were recorded in all the tested organs during summer when the animals are in the spawning period, suggesting that clams could accumulate proteins and lipids. Regarding the environmental factors, a negative and a significant correlation was recorded between glycogen, lipid contents and water temperature. Based on these results and as M. stultorum is appreciated by the consumers, we suggest that the harvesting of M. stultorum should be concentrated on February to June when the whole body was characterized by an important amount of the biochemical composition when the seafood is at its highest nutritive value as compared to August to January. Because of its high nutritive value especially it’s richness by some important and essentials fatty acids, M. stultorum seems to be considered as an important commercial species in many countries and in Tunisia particularly. We suggest that harvesting of M. stultorum should be concentrated on the period when the seafood is at its highest nutritive value. survivability rates from malignancy. The greatest variations in the mortality ratios existed within the European countries.