Control of brackish water fouling mussel, Mytilopsis leucophaeata (Conrad), with sodium hypochlorite.

Though the Conrad's false mussel, Mytilopsis leucophaeata, is an important fouling animal in industrial cooling water systems, there are no published reports on the tolerance of this species to chlorination. A series of experiments was conducted to determine the effects of mussel size (2-20 mm shell length), season (breeding versus nonbreeding), nutritional status (fed versus starved) and acclimation temperature (5-30 degrees C) on the mortality pattern of M. leucophaeata under continuous chlorination (0.25-5 mg/L). The effect of mussel size on M. leucophaeata mortality in the presence of chlorine was significant, with 10 mm size group mussels showing greater resistance. At 0.25 mg/L residual chlorine, 2 mm size group mussels took 89 days to reach 100% mortality, whereas 10 mm size group mussels took 109 days. M. leucophaeata collected during nonbreeding season (December-April) was more tolerant to chlorine than those collected during breeding season (June-October). Nutritional status of the mussel had no significant influence on the chlorine tolerance of the mussel: fed and starved mussels succumbed to chlorine at equal rates. The effect of acclimation temperature on M. leucophaeata mortality in the presence of chlorine was significant. At 0.5 mg/L residual chlorine, mussels acclimated at 5 degrees C required 99 days to reach 95% mortality, whereas mussels acclimated at 30 degrees C required 47 days. A comparison of present data with previous reports suggests that resistance of M. leucophaeata to chlorination is higher than other mussel species causing fouling problems in The Netherlands ( Mytilus edulis and Dreissena polymorpha).