Open Collections

Hendriks, Brian James Lambert

University of British Columbia

I used acoustic tags with depth sensors and a series of sentinel underwater acoustic receiver arrays to track adult Chinook salmon (Oncorhynchus tshawytscha) through the southern Salish Sea towards their natal rivers. My objectives were to: i) identify areas and routes most utilized by migrating salmon, ii) determine travel times and rates between areas, and iii) identify depth distributions exhibited by migrating Chinook salmon. I tagged 114 adult Chinook salmon, from 14 different river systems, nearshore to Port Renfrew, BC during the summers of 2019 and 2020. Based on migration path criteria, 35 individuals took direct routes towards natal rivers, 35 individuals took non-direct routes, and 44 could not be categorized. Only Fraser River fish consistently took direct paths towards their natal river. Tagged fish were largely detected in the surface waters between 0-30 m (mean 22.0 m) throughout all areas of study, rarely detected below 100 m, and were orientated primarily nearshore. Average migration rates varied among stocks from 0.25 BL/s to 0.65 BL/s (0.84 to 2.02 km/h). There were no effects of somatic energy index, sex, or year on these rates. Fraser River Chinook slowed as they approached their natal river, with an average migration rate 3 times faster in Juan de Fuca Strait (0.66 BL/s; 2.09 km/h) compared to the Fraser estuary (0.22 BL/s; 0.67 km/h). Fraser River Chinook salmon are significant prey to Southern Resident Killer Whales (SRKW; Orcinus orca) but did not seem to exhibit any different behaviours in terms of migration rates or depth patterns through known SRKW feeding regions relative to other areas. The survival of tagged Fraser River fish was relatively high through all segments. The fact that Fraser fish migrated at some of the fastest rates observed might indicate some form of anti-predator behaviour. Alternatively, these fast migration rates may reflect an urgency to reach the Fraser River and initiate arduous freshwater migration prior to spawning. This study is the first to describe migration behaviours of several stocks of adult Chinook salmon during their homeward marine migrations by providing detailed insights into migration routes, rates, and depths.

Text

2024-07-29

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88728

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/