Survival analysis of tethered juvenile sea scallops Placopecten magellanicus in field experiments: Effects of predators, scallop size and density, site and season
Date
1994
Authors
Barbeau, M. A.
Scheibling, Robert Eric
Hatcher, B. G.
Taylor, L. H.
Hennigar, A. W.
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Abstract
The impact of predation on survival of juvenile sea scallops Placopecten magellanicus has
important implications for the population dynamics and aquaculture of this species. In field
experiments using tethered juvenile scallops, we examined the effect of biological and physical
factors, such as prey size, predator and prey density, water temperature (season) and site, on
mortality rates of scallops in Lunenburg Bay, Nova Scotia, Canada. The major predators of juvenile
scallops were crabs Cancer irroratus and sea stars Asterias spp. In an experiment manipulating
scallop density, crab predation rate increased significantly with scallop density, but crab density
did not, suggesting a functional response. Sea star predation rate on scallops was not affected by
scallop density. In a series of experiments with different size classes of scallops tethered at
different sites and seasons, and in different densities of surrounding scallops and predators, the
effects of covariates on scallop survival times were assessed using the statistical procedure of
survival analysis. Since the tethering technique affected crab and sea star predation differently,
the competing causes of scallop mortality were analysed separately. Water temperature, site, and
scallop density were the important variables affecting crab predation. There was a significant
interaction between temperature and site, such that crab predation on scallops increased with
temperature at one site and was independent of temperature at the other site. Predation by crabs
also increased with scallop density and, to a lesser extent, with crab density. Water temperature
and scallop size were the primary variables affecting sea star predation. Sea star predation on
scallops increased with temperature and decreased with scallop size. The results of this study
suggest options for minimizing predation of scallops by crabs and sea stars in bottom culture
operations.
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Citation
Barbeau, M. A., R. E. Scheibling, B. G. Hatcher, L. H. Taylor, et al. 1994. "Survival analysis of tethered juvenile sea scallops Placopecten magellanicus in field
experiments: Effects of predators, scallop size and density, site and season." Marine Ecology Progress Series 115(3): 243-256. doi:10.3354/meps115243