Environmental factors influencing the growth and survival of juvenile sea scallops, Placopecten magellanicus (Gmelin, 1791)

Frenette, Bruno (2004) Environmental factors influencing the growth and survival of juvenile sea scallops, Placopecten magellanicus (Gmelin, 1791). Masters thesis, Memorial University of Newfoundland.

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Abstract

In southeastern New Brunswick, located along the Northumberland Strait, shellfish aquaculturists are interested in the option of cultivating sea scallops, Placopecten magellanicus, in shallow water embayments, along with oysters and or mussels. However, sea scallops are not naturally found in the shallow waters of southeastern New Brunswick and environmental conditions at these sites may not be suitable for their culture. The objectives of this study were to investigate the potential for scallop culture in these environments. Laboratory studies were undertaken using two size classes of juvenile scallops (10.0-20.0 mm and 20.1-35.0 mm shell height) to determine their salinity and temperature tolerances. Results indicated that 100% survival was found in salinities ≥25 ppt, and temperatures ≤18°C. The health status of the surviving juvenile scallops was assessed by measuring clearance and ingestion rates, oxygen consumption and secretion of stress related enzymes. The highest indicators for these physiological parameters were observed at 13°C at ambient salinity which was above 30 ppt. -- Field studies were undertaken using the same size classes to examine scallop growth and survival and environmental parameters in four bays, ranging in minimum depth from 3-7 m, in southeastern New Brunswick which are characterized by heavy freshwater inflow during spring and high temperatures (≥20°C) in summer. The scallops held in Bouctouche Bay had the highest survival after 13 months, 84.3% for small juveniles and 88.1% for large juveniles. Lowest percent survival values (0.0 %) were observed in Little Shemogue Bay, Richibucto Bay (sites 2 and 3). The growth rate for small juvenile scallops was the highest in Richibucto Bay (site 1) and Bouctouche Bay (0.061 mm/d ± 0.006 and 0.057 mm/d ± 0.001, respectively). Whereas, for large juvenile scallops the highest growth rate was recorded in Cocagne Bay (0.075 mm/d ± 0.008). -- Overall, based on growth, survival and environmental parameters (mainly salinity), Bouctouche Bay has the best potential of the sites tested for the development of a sea scallop aquaculture site. It is concluded that sea scallop aquaculture farming has a limited future in the region of southeastern New Brunswick. It may be possible, however, at some sites in which the environmental parameters are found to meet criteria that are proposed in this study.

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