Mapping capelin demersal spawning habitat off northeast Newfoundland

Roy, Andre (2013) Mapping capelin demersal spawning habitat off northeast Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Habitat mapping is an essential tool for the management and conservation of our marine resources. In this study, multibeam echosounders, which have become important instruments for the mapping of benthic habitat, were used to map capelin demersal spawning sites along the northeast coast of Newfoundland. The EM3000 multibeam echosounder was used in this study to survey an area near Cape Freels containing five known capelin spawning sites. Two types of information were extracted from the acoustic multibeam data: bathymetry, providing a high resolution grid from which the morphologic characteristics of the spawning site could be extracted; and backscatter information, providing a proxy for the substrate grain size. -- Studying the morphology of the spawning sites revealed that spawning is taking place on flat areas of the seafloor with a slope value of generally less than 2° and a rugosity ratio of less than 1.19. The spawning sites are situated inside depressions, confirming the findings of a previous study using single-beam sonar data. The backscatter information was used to identify the grain size of the spawning substrate, which varies from medium sand to pebble, to delineate the areas of suitable substrate in the study area. Maps identifying areas suitable for capelin spawning were compiled from the morphologic characteristics. It is estimated that 32% of the seafloor in the study area is suitable for capelin spawning. In 53% of the area, the grain size of the substrate is too large to be suitable for spawning; 5% has finer than suitable substrate; and 10% of the seafloor could not be classified. The multibeam data provided all the information necessary to build habitat maps showing the areas of the seafloor which could potentially support demersal spawning.

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