Distribution of harp seals, Phoca groenlandica, off Newfoundland and Labrador in relation to abiotic and biotic conditions

Lacoste, Karine (1997) Distribution of harp seals, Phoca groenlandica, off Newfoundland and Labrador in relation to abiotic and biotic conditions. Masters thesis, Memorial University of Newfoundland.

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Abstract

This study provides the first quantitative assessment of the yearly distributions of harp seals in the northwest Atlantic, particularly during the winter. Recent abiotic and biotic changes in the northwest Atlantic concurrent with reports of seals sighted further offshore have prompted this investigation on harp seal distributions in relation to environmental factors. Seal sighting data were collected from 1991 to 1995 using line-transect techniques. Data were standardized for effort and sighting conditions and grouped by subareas of 1 degree². Numbers of seals observed were estimated using a relative group size category. Visual appraisals of data were made using a Geographical Information System. The winter distributions of harp seals were overlaid onto maps of sea ice, sea floor inclination, sea surface temperature, and several prey distributions. The influence of these variables was tested using a generalized linear model, ANOVA, and correlation, respectively. The influence of water depth at location of seal sightings was also investigated. -- Offshore areas are an important habitat for harp seals. The winter distributions of harp seals showed similar patterns during 1991-1993, but shifted slightly to the southeast during 1994-1995. Water temperatures were found to be within the thermoneutral limits for this species at all locations and for all winter years. Although there was a tendency for seals to be observed along the continental slope edge and in specific ice conditions, no significant differences were found between locations of seals and sea floor inclination or ice characteristics. Seals were mainly seen in waters of depths ranging from 300 to 500 m, values known to be within their diving range. Sea floor topography and water depth were the only environmental variables that remained constant throughout the 1991-1995 winter distributions. The spatial distribution of prey investigated concurred with the documented diet of harp seals. Further investigations will be needed to quantify the relationship existing between them.

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