Seventy-eight harbour porpoises, Phocoena phocoena, (33 females, 45 males) were obtained from the summer (June-September) cod fishery incidental-by-catch in the Gulf of St. Lawrence, and examined for the presence of cranial sinus nematodes. This is the first quantitative and in-depth study of the distribution of Stenurus minor (Kuhn, 1829) Baylis and Daubney, 1925 in the cranium of by-caught harbour porpoises. Stenurus minor was present in the cranial sinuses of all adult porpoises ($>$1yr, n = 66, x = 2362, range 87-8920) and absent in all young-of-the-year ($<$1yr, n = 12). Only fifth-stage worms were observed and these were equally distributed between the right and left side ot the skull (mean intensity = 1158 and 1213 in the left and right side, respectively). Female S. minor were predominant (1:1.8 sex ratio). Mean intensity of S. minor was similar among all infected porpoises, suggesting an annual loss and recruitment of this parasite. Parasite load had no apparent effect on porpoise body condition (measured as % blubber weight of carcass). No gross lesions associated with the presence of numerous S. minor in the cranial sinuses, were observed. There was an inverse relationship between the intensity of S. minor and mean worm-length, suggestive of a "crowding effect". Mean worm-length in lightly infected porpoises was 17.8 $ pm$ 0.2 mm and 16.1 $ pm$ 0.2 mm in heavily infected animals. Possible life-cycles and modes of transmission are examined in light of our findings. The absence of S. minor in porpoises less than 1 year old suggests heteroxenous transmission of this parasite, via an intermediate host in the food chain. Transmammary and or transplacental transmission is unlikely.

No description available.

A prevalence of 76% and a mean intensity of 42.7 Anisakis simplex was found in harbour porpoises (Phocoena phocoena) (N = 78) by-caught in cod gill nets set by fishers from the Gaspe area in summer 1993. No young-of-the-year porpoises (N = 12) were infected. Prevalence and mean intensity among immature and adult porpoises as well as between sexes and length-classes were not significantly different. Anisakis simplex was present in the three stomach compartments of harbour porpoises. Adult stages were proportionately less abundant in the main and pyloric stomachs than the forestomach. Percent intensity of A. simplex was influenced by maturity of harbour porpoises. Gravid female A. simplex contained up to 818,000 eggs. Egg number was highly correlated with worm uttering volume. Density effects were not demonstrated, possibly due to high variability of egg number, total length, uterine and total worm volume between parasites from each stomach and between stomachs of harbour porpoise.

No description available.