GROWTH OF EXPERIMENTALLY CULTURED OCEAN QUAHOGS (Arctica islandica L.) IN NORTH TEMPERATE EMBAYMENTS

The growth of metamorphosed ocean quahogs (Arctica islandica L.) of known age reared from larvae settled in October 1980 was monitored over a 16-month period using experimental containers suspended from fixed and floating structures in two embayments on the coast of Maine. Specimens ranging in length (maximum antero-posterior dimension) from 1.8 to 4.3 mm (n = 119; mean=2.5 mm; std. dev. = 0.4 mm) were placed in the containers in June 1981. Shell length measurements were recorded at monthly intervals until October 1982. Water temperatures at the experimental sites ranged from a low of 0.1°C during January 1981 to a high of 21.4°C during July 1982. Maximum growth rates (1.8 to 2.3 mm/month) were observed during the warmest months (June through October). Reduced, yet measurable, amounts of shell (0.3 to 0.5 mm/month) were deposited during even the coldest winter months (January and February). Natural mortality over the 16-month experimental period was less than 10%. Numerous specimens were randomly sacrificed during the experimental period for subsequent analyses of internal shell growth patterns. By late October 1982 the lengths of the remaining specimens (n=53) ranged from 11.4 to 33.7 mm (mean=26.0 mm; std. dev. = 4.1 mm). Although recorded growth rates are considerably faster than those heretofore reported for Arctica islandica, the growth potential of this species in a suspended culture system does not appear to be high enough to warrant seriously considering this species as a commercial aquaculture candidate.