Research Document - 2005/030
Harbour seals in Newfoundland and Labrador: a preliminary summary of new data on aspects of biology, ecology and contaminant profiles
By B. Sjare, M. Lebeuf, G. Veinott
Abstract
Little is known about the current status of harbour seals (Phoca vitulina) in Newfoundland and Labrador given the last, and only comprehensive, study was conducted in the 1970s. Based on a limited number of reconnaissance boat surveys, opportunistic shore-based haulout counts and interviews with fishermen during 2001-2003, the current distribution of harbour seals is generally consistent with observations made in the 1970s. There is also limited evidence suggesting that local abundance of seals at some known haulout sites in the more southern portions of the province may have increased while abundance at sites in more northern areas of the west, northeast and Labrador coast are generally consistent with reports from the 1970s. Analyses of stomach samples collected from 1985-2003 indicated harbour seals consumed a wide variety of fish and invertebrate prey, but ten fish species accounted for almost 95% of the wet mass of food consumed. Winter flounder, Arctic cod, shorthorned sculpin and Atlantic cod were the most important overall. However, there was evidence of regional variation in the diets of seals sampled from the south, west, northeast and Labrador coasts. Seals fed on fish prey that were 10.4–41.3 cm in length (mean=18.8 cm, SD=6.80). From 2001-2003, a total of 66 tissue samples were collected from harbour seals throughout the province and analysed for heavy metal, trace elements and persistent organic pollutant (POPs) contaminant levels. The relative differences in heavy metal concentrations among tissue types were consistent with values in the published literature. The mean within-sample site concentration of trace elements, and the range among sites in Newfoundland and Labrador, corresponded well with data from harbour seals in Alaska and with northern pinnipeds in general. The trace elements Hg, Se, and Cd showed the greatest variability within and among sampling sites. Changes in renal cadmium concentration with body size were dependent on site; higher concentrations being found in seals sampled along the south and east coasts of the province. The source of cadmium is unknown at this time but it may be Placentia Bay, or alternatively, contaminants are being transported along the southern coast of the province and into Placentia Bay from the St Lawrence River. Based on the suite of persistent organic pollutants (POPS) examined, harbour seals sampled from Newfoundland waters were less contaminated than those from the St Lawrence Estuary population and generally similar to those from the Southern Gulf of St. Lawrence. Mirex and ΣPCB concentrations were 5-10 times higher in the Estuary population while Σ DDTs and Σ Chlordanes were 2-5 times higher than in Newfoundland seals. Similar PCB patterns and POP proportions were observed among Newfoundland seals of the same sex and age category suggesting that animals were permanent residents of a limited geographic area from which they extracted POPs. Mature males had higher POP levels than females, but there were no differences between male and female young of the year and juveniles. These new data on the general distribution, local abundance, diet and initial contaminant profiles of harbour seals will provide a basis for future ecological studies, population assessments and for understanding how contaminants accumulate in coastal food chains in eastern Canada.
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