Research Document - 2003/079

Stock separation of narwhal (Monodon monoceros) based on organochlorine contaminants

By B.G.E. de March and G. Stern

Abstract

This document describes organochlorine contaminants (OCs) in narwhal tissue, analysed for the purpose of stock discrimination, with data available in August 2003. Canonical discriminant function analysis using 14 OC groups separated narwhals hunted in Repulse Bay, Broughton Island, Pond Inlet and Grise Fiord. Canonical functions were most strongly correlated with the concentrations of several PCB congeners and DDT compounds. While narwhals from all sample locations had overlapping OC contaminant concentrations, OC ratios differed. Repulse Bay narwhals were the most distinct, with overall lower OC levels and high PCB/DDT ratios. Narwhals from Broughton Island had relatively high OC levels and high PCB/DDT ratios. Narwhals hunted in Pangnirtung may be from the same stock as those hunted in Broughton Island. Narwhals from Clyde River were not convincingly associated with or separated from other groups; however this may be due to the small sample size of six animals. Among the 4 major sample groups, narwhals from Pond Inlet and Grise Fiord were the most similar. However, narwhals from Pond Inlet had a notably lower PCB/DDT ratio than those from Grise Fiord. These differences are assumed to be due to food web differences. Several hypothesized stock differences, existing scientific knowledge, and traditional knowledge are confirmed by the results presented here.

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