Vladimir E. Kostylev

Stock evaluation of giant scallop (Placopecten magellanicus) using high-resolution acoustics for seabed mapping

Abstract Survey designs in use for the evaluation of sea scallop stocks do not consider the variability of sediment type, despite strong evidence of its importance for the recruitment and survival of scallops on the sea floor. This study examines the distribution of scallops on Browns Bank, Scotian Shelf, at two test sites, in comparison to sea floor sediment distribution, with particular attention to the effects of small-scale sediment variability on the abundance of the commercially exploited scallop. Important links between scallop abundance, sediment type and habitat structure are described. Scallops are strongly associated with gravel lag deposits, which are readily distinguishable from sand-covered terrain through the use of multibeam backscatter data. There exists a highly significant correlation between scallop survey catch rates and backscatter intensity which can be used for the prediction of scallop stock abundance. Developments in underwater acoustics enable for more precise sea floor mapping and contribute to better estimates of scallop abundance.

Chapter 2 Continental shelves of Atlantic Canada

Abstract The wide continental shelves of Atlantic Canada are characterized by a series of banks separated by transverse troughs. These shelves have been imprinted by repeated Quaternary glaciations, so that fluvial valleys have been deepened into fjords and shelf-crossing troughs, and a suite of glacigenic sediments has been deposited. In shallow areas the seafloor is shaped by waves and currents, including the strong tidal currents of the macrotidal Bay of Fundy. Glacigenic sediments have been reworked by modern processes to yield thick muds in basins, and thinner deposits of sand and gravel on wave-dominated banks and the littoral zone. As a result of a cold climate and the Labrador Current, seasonal sea ice occurs to varying degrees across the region, and iceberg impact continues on much of the Newfoundland and Labrador shelves. For the purpose of description, we divide Atlantic continental shelves into four regions and focus on advances in understanding over the past several decades relating to: (1) processes on upper continental slopes; (2) glacial history in the last glacial cycle; (3) glacial land systems; (4) geographical changes caused by glacio-isostasy; and (5) sediment mobility on the offshore banks. We conclude with a brief overview of the biota.