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Understanding the spatial and temporal dynamics of the fish-assemblage structure of estuaries is indispensable in conservation and habitat-improvement efforts. This study reports seasonal as well as spatial dynamics of fish diversity of the Waikouaiti Estuary and indicates the key physicochemical variables that influence the ichthyofauna of the estuary. Fish were collected from upper, middle and lower reaches of the Waikouaiti Estuary monthly for 1 year, by using a seine net. In total, 15 species and 4967 individuals were collected during the study period. Distinct differences in ichthyofaunal composition, driven by spatiotemporal environmental heterogeneity, were observed between the three reaches of the Waikouaiti Estuary. Fish abundance was higher in the middle reach where the water is turbid. Whereas fish species with diadromous life history occurred more frequently in the upper reach of the estuary, marine-migrants and marine-stragglers were abundant in the lower reach. The present study indicated that salinity and turbidity were the best predictors of fish species composition in the different reaches of the Waikouaiti Estuary.

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This experiment was conducted to evaluate the synergistic effects of vitamin C and E on methylmercury (MeHg) toxicity in juvenile olive flounder Paralichthys olivaceus. In a 3×3 factorial design, 9 experimental diets containing three different vitamin C (0, 200 or 400 mg/kg diet in the form of l-ascorbyl-2-monophosphate) and vitamin E (0, 100 or 200 mg/kg diet in the form of dl-α-tocopheryl acetate) levels with the Hg toxicity level (20 mg/kg diet in the form of MeHg) were formulated. Triplicate groups of fish averaging 2.3 ± 0.05 g (mean ± SD) were fed one of the 9 diets in a flow through system for 8 weeks. Fish fed 400 mg vitamin C/ kg diet with 100 or 200 mg vitamin E/kg diet showed significantly (P < 0.05) higher weight gain (WG) than did fish fed the other diets. Fish fed 400 mg vitamin C/kg diet at all vitamin E levels and those which fed vitamin C and E equally at a rate of 200 mg/kg diet showed significantly (P < 0.05) higher feed efficiency (FE), specific growth rate (SGR) and protein efficiency ratio (PER) than did fish fed the other diets. Fish fed 200 and 400 mg vitamin C/kg diet exhibited significantly (P < 0.05) lower Hg concentration in their muscle as well as kidney than did fish fed the other diets. Therefore, these results clearly indicated that the synergistic effects of these two vitamins on MeHg toxicity by supplementing dietary vitamin C (200 and 400 mg/kg diet) with vitamin E (100 and 200 mg/kg diet) in juvenile olive flounder.