COMBINED EFFECTS OF DISSOLVED OXYGEN AND SALINITY ON GROWTH AND BODY COMPOSITION OF JUVENILE GREEN-LIPPED MUSSEL PERNA VIRIDIS

The green-lipped mussel Perna viridis is distributed widely in estuarine and coastal areas of the Indo-Pacific region and is regarded as a cultured mussel or by-product in aquaculture. However, in estuarine and coastal waters where salinity varies with freshwater input and rainfall during the wet season, hypoxia frequently occurs, especially when waters are highly eutrophic. The current study aimed to evaluate the effects of two key environmental factors in estuarine and coastal waters-dissolved oxygen (DO) and salinityon growth and body composition of juvenile green-lipped mussels P. viridis. Parameters studied included shell length (SL), tissue dry weight (TDW), condition index (CI), specific growth rate (shell length, SGR_L ; tissue dry weight, SGR_W), moisture content (MC), crude protein (CP), crude fat (CF), crude carbohydrate (CC), crude ash (CA), and energy content (EC). Mussels were cultured for 6 wk at 4 salinities (15, 20, 25, and 30) and 3 dissolved oxygen concentrations (1.5 ± 0.3, 3.0 ± 0.3, and 6.0 ± 0.3 mg 0₂/L) in a 4 × 3 factorial design. All growth parameters (SL, TDW, CI, SGR_L, and SGR_W) decreased under reduced DO and salinities, but interactive effects between these 2 factors were statistically indistinguishable except for SGR_W. Higher percentages of CF and CP, and lower percentages of CC were obtained at reduced salinities and DO. When changes in biochemical content (weight per individual) were compared, both CP and CC content decreased significantly as salinity or DO decreased, whereas no pattern was observed for CF. EC (calories per gram) was not significantly different among DO treatments, but varied significantly with salinity. Total energy content (calories per individual), however, increased significantly with both DO and salinity, but the interaction between salinity and DO was statistically indistinguishable.