DISTINGUISHING BETWEEN POPULATIONS OF FRESH-WATER AND SALT-WATER HARBOR SEALS (PHOCA-VITULINA) USING STABLE-ISOTOPE RATIOS AND FATTY-ACID PROFILES

Stable-isotope ratios and fatty acid profiles were used to determine w hether the Lacs des Loups Marins harbour seal (Phoca vitulina mellonae ) on the Ungava peninsula of northern Quebec (160 km east of Hudson Ba y) could be distinguished from populations of its marine counterparts, Phoca vitulina concolor and Phoca vitulina richardsi. Phoca v. mellon ae had a lower mean delta(13)C value than P. v. concolor (p < 0.0001). Seals from a P. v. concolor population from Lake Kasegalik, N.W.T., t hat have access to both freshwater- and marine-derived carbon had a me an delta(13)C value intermediate between that of P. v. mellonae and ma rine P. v. concolor and were distinguishable from bath. Phoca v. mello nae's blubber contained significantly higher levels of 18:2n-6, 18:3n- 3, 20:4n-6, C-18 polyunsaturated fatty acids, and total polyunsaturate d fatty acids than the blubber of harbour seals from two marine popula tions, and significantly lower levels of 20:1n-9 and 22:1n-11. The n-3 /n-6 ratio of P. v. mellonae was also significantly lower than that of its marine counterparts. These findings all indicate that the Lacs de s Loups Marins harbour seal subsists primarily on a diet derived from freshwater species.