An Investigation of Cowichan Coho Run Timing and Marine Survival

Cowichan River Coho have received little attention in recent times despite significant historical abundances and focused stock assessment work on Chinook. Chum returns have been strong enough to support commercial fisheries in terminal areas over the last decade. Interception of adult Coho in Chum fisheries is a growing concern yet little information exists on run timing. We propose to apply PIT tags to Cowichan River Coho smolts in order to take advantage of the permanent in-river detection system installed in 2016 for Chinook research. It is anticipated that detection of tags inside of jacks and adults will allow run timing curves to be established. Similarly, marine survival estimates can be derived provided tag detection efficiency is known. Objectives in years’ three to five include investigating methods to enumerate adults using the same technology in a system where reliable escapement estimates are difficult to produce.