Green mussels (Perna viridis L.) of the family Mytilidae are commercially important bivalve molluscs. The mussels were reported to occur on almost all rocky beaches along the Sind and Baluchistan coasts of Pakistan. The intertidal portion of the exposed rocky shore at Paradise Point, the present study site, harbours a large population of P. viridis. The present investigation provides first-hand basic information about many aspects of bioecology of P. viridis from northern Arabian Sea.
The present dissertation consists of seven chapters dealing with population structure, growth, condition index, biochemical composition, amino acids, metal concentration and associated fauna of mussel bed. A comprehensive review of the literature on mussels, together with the objective and importance of the present study is also given in the chapter, "General Introduction" .
The population of green mussels at Paradise Point remained stable most of the year with recruitment in July and November. Allometric studies demonstrated that relationship between length and width of shell changed with the season; in some months length increased isometrically with the width and in others the shell length increased faster than width. Increase in shell length was faster than shell weight in all seasons. Shell length increased faster than shell height. A clear seasonal trend in length to dry tissue weight was observed. Dry tissue weight increased isometrically with length in one half of the year but showed negative allometry in the other part.
Observations on condition index showed that peak value was found in November which was twice the minimum value noted in March. The condition index increased with increase in size of the mussel in winter. Results of nutritive assessment indicated 58 to 66.5 percent protein, 4.6 to 9.8 per8ent lipids and 14.7 to 29.2 percent carbohydrates. The protein of P. viridis contained all essential amino acids; arginine and aspartic acid were present in highest and lowest amounts, respectively. The average concentrations of Fe, Cu, Zn, Cd, Ni and Pb were 404, 16.7, 112.5, 4.4, 9.8 and 2.2 p.g/g dry tissue weight, respectively. Concentrations of heavy metals in mussels of four different sites were quiet different from each other. Higher levels were found in mussels of Sandspit and Native Jetty where pollutant load was very high.
The mussel community of Paradise Point consisted of fifty seven species of invertebrates belonging to eight phyla, and nine species of algae. Ninety five percent of fauna belonged to three phyla, Arthropoda - 52.5%, Mollusca - 31.8% and Annelida10.5 %. Species richness and diversity were high in winter months (February and November).