Dispersion and mortality of a population of sea scallop (Placopecten magellanicus) seeded in a tidal channel

Ten thousand scallops (Placopecten magellanicus) from 4 to 26 mm shell height were released in 40 m² of an 8 m deep tidal channel in Lunenburg Bay, Nova Scotia, Canada. Their survival, distribution, and potential predators were monitored during the 13 months following release in November 1990 using quadrat and video surveys. Both dispersion and mortality were rapid during the first 2 weeks, when predation by crabs and starfish was estimated to have killed about one half of the seeded population. The rate of loss decreased markedly over the following winter and spring. Dispersion of seeded animals increased again through summer and autumn, producing a final scallop density of about 2 m^-2 (twice that of the natural population), covering more than 3500 m² of seabed. This expansion was accompanied by little further mortality, and the final estimate of survivors in the expanded survey area was 40%. Scallop displacement was directional, but the mean vector did not match that of the dominant, near-bed water currents. The average growth (shell height increment) of surviving scallops was 35 mm in 13 months. Our results demonstrate the potential for ecologically viable bottom culture of the species in coastal Nova Scotia.