EFFECTS OF THE BRAIN PARASITE MYXOBOLUS-ARCTICUS ON SOCKEYE-SALMON

Parasitism with Myxobolus arcticus did not affect smolt size of sockey e salmon or their osmocompetence, but had a deleterious effect (P<0.00 1) on the swimming speed of naturally infected smolts. Parasitized fis h had a mean swimming speed of 2.89 fork length s(-1) (L-F s(-1)) comp ared with 4.37 L-F s(-1) for unparasitized fish. The parasite probably impairs swimming ability by affecting the central nervous system, but this effect does not appear severe enough to limit the parasite's use fulness in stock separation. (C) 1998 The Fisheries Society of the Bri tish Isles.