Effect of deployment date and environmental conditions on growth rate and retrieval of hatchery-reared sea scallops, Placopecten magellanicus (Gmelin, 1791), at a sea-based nursery

摘要

The effect of date of deployment on growth and subsequent retrieval of hatchery-reared scallop spat from a land-based hatchery to a sea-based nursery was studied to provide information for management of juvenile-size scallops, ranging from 1.4-7.0 mm in shell height. The objective of this study was to determine the optimal time period for spat deployment to a sea-based nursery to yield commercially acceptable growth rates and retrieval (scallops remaining after mortality and loss through nets). Spat of the same size class and stocking density were deployed over five consecutive 16-23 day intervals beginning in August 1997. Environmental factors were monitored weekly. Scallops were sampled after each deployment period for determination of shell height and retrieval. Scallops were then re-deployed and sampled before (November) and after (June) the winter season. Results demonstrated that there were significant differences in scallop growth and retrieval among the five consecutive deployments. Only scallops that had been deployed in August were greater than 7 rum by November and could be sorted and transferred to larger mesh equipment for ongrowing prior to winter. The findings of this study demonstrated that early deployment (August) to sea-based nursery yielded high growth rates and retrieval. Deployment later than early September required over-wintering in nursery culture before transfer to ongrowing. Significant correlations were found between both growth rates and retrieval and some of the environmental parameters (e.g., temperature, chlorophyll-a, particulate organic matter). Acclimation to the new farm conditions may be necessary for nursery-sized scallops to adjust physiologically without a major lag in growth following transfer from the hatchery to the sea.