Olfactory Sensitivity during Parr and Smolt Developmental Stages of Coho Salmon

Abstract

The avoidance response of juvenile coho salmon Oncorhynchus kisutch to L-serine and D,L-alanine was measured in a two-choice Y-trough. Threshold concentration for olfactory detection and avoidance of L-serine was 10−8 M for zero-age parr, 10−7 M for yearling parr, 10−5 M for smolts in late April-early May, and 10−6 M for smolts in June. Threshold for the avoidance of D,L-alanine was 10−7 M for yearling parr, 10−6 M for smolts in late April-early May, and 10−5 M for smolts in June. These data suggest that (1) heightened olfactory sensitivity may not occur during smoltification or (2) smolts may be less disposed than parr to show avoidance behavior.