Seasonal variation in the reproductive activity, physiological condition and biochemical components of the brown mussel Perna perna from the coastal waters of Yemen (Gulf of Aden)

Gametogenic cycle, gross biochemical composition, condition indices and soft tissue caloric value of the brown mussel Perna perna were investigated in the coastal waters of the Gulf of Aden over ten months, to delineate ecophysiological performance of the bivalve. The timing of reproductive activity and seasonal variations of physiological features appear to depend on interaction of environmental (exogenous) and internal (endogenous) factors. Two major spawning events occurred during seasonal monsoons i.e. in late summer (SW monsoon, August-September) and early spring (NW monsoon, February-March), although these differed considerably in relative intensity and the extent of the resulting changes in physiology and body weight. The summer breeding, which was correlated with low water temperature and abundant food, exerted little effect on biochemical constituents, indicating protracted and portioned spawning. Reserve stores (lipids, carbohydrates and proteins) accumulated gradually in the cooler inter-monsoon period of gametogenic quiescence, to provide energy for periods of natural nutritional stress when water temperature increased and primary production diminished. The second spawning in spring was accompanied by a substantial decrease in lipids, carbohydrates and condition indices of the mussels probably due to the release of nutrient-rich gametes in adaptive response to lower food availability in the environment. High reproductive effort presumably induced increased mortality of females, which were strongly outnumbered by males at a ratio of 1.8:1.0. Caloric value of this mussel falls within a range typical for mussel species in other subtropical areas, highlighting the importance of Perna perna as a local food resource and its potential suitability for aquaculture.