Polydorid infestation in the flat oyster, Tiostrea chilensis:: hyposaline treatment for an aquaculture candidate

Attempts to commercially farm the Chilean oyster, Tiostrea chilensis in New Zealand are hampered by high levels of shell infestation by the polydorid polychaete, Boccardia acus. Wild stock in the warmer, northern waters of New Zealand typically present a mean of 8.6 +/-,0.7 worms per right upper valve from an early stage of development (similar to 17 mm shell height). Both hypersaline and freshwater treatments were effective in reducing worm numbers, but freshwater treatment for 180-300 min was most effective and resulted in > 98% worm mortality without producing any obvious harmful effects on the oyster. Hyposaline treatment is therefore recommended as a simple and cost-effective method for the control of B. acus in farmed T. chilensis.