Upper Thermal Limits to Migration in Adult Chinook Salmon: Evidence from the Klamath River Basin

Abstract

Temperature-sensitive transmitters and archival tags allowed precise measurement of adult Chinook salmon Oncorhynchus tshawytscha responses to high water temperatures and other environmental variables in the Klamath River basin during 2004 and 2005. Mean daily river temperatures upon initiation of upriver migration by adult Chinook salmon after a period of thermally induced migration inhibition ranged from 21.88C to 24.08C (mean ¼ 22.98C). During the first week (168 h) of migration, mean average body temperature was 21.98C, mean average minimum daily body temperature was 20.68C, and mean average maximum daily body temperature was 23.18C. Temperatures above these levels appeared to completely block migration in almost all circumstances. Migration was inhibited at lower mean daily river temperatures during periods of increasing river temperatures than during periods of declining river temperatures. The ability of adult Chinook salmon to correctly gauge the onset of periods of declining or inclining river temperature is a vital mechanism for taking advantage of brief thermal windows for upriver migration. Weather fronts were responsible for periods of declining river temperature, but no precipitation or consistent drops in atmospheric pressure were associated with these weather fronts or with fish movements. The associated decrease in light levels, however, appeared to serve as an indicator of impending reductions in river temperatures for adult Chinook salmon. Changing river discharge had a negligible influence on migration behavior, and hypoxia sufficient to inhibit upriver migration (i.e., dissolved oxygen , 5 mg/L) never occurred during the study. The upper thermal limits to adult Chinook salmon migration as indicated by results from the Klamath River basin are substantially higher than previously reported in the literature and approached or exceeded the highest ultimate upper incipient lethal values determined for any life stage of this species.

Thermal exposure of adult Chinook salmon in the Willamette River basin

“…Several salmon used this site for up to $ 36 h when the Willamette was 418°C, a duration similar to what has been reported in other Chinook salmon studies (e.g., Goniea et al, 2006;Strange, 2010). In other main stem reaches, salmon body temperatures rarely fell more than 1°C below the minimum daily temperatures at nearby USGS gages despite the opportunity presented by several cool-and cold-water patches along the migration corridor.…”

“…It is perhaps more likely that the imperative to reach spawning tributaries motivated most salmon to bypass refuge sites in favor of shorter total migration time. The motivation hypothesis has been suggested in other Chinook salmon studies (e.g., Brannon et al, 2004;Strange, 2010Strange, , 2012 and is consistent with a life history strategy of early migration to avoid seasonal peak temperatures followed by prespawn staging in cooler sites until reproductive conditions are most favorable (Healey, 1991;Quinn, 2005).…”

“…However, more recent research suggests that thermal migration barriers may occur at higher thresholds in some southern populations. Just south of the Willamette basin, for example, many radio-tagged Klamath River Chinook salmon (stream-and ocean-type) initiated or continued to migrate in water temperatures Z23°C (Strange, 2010(Strange, , 2012. Just northeast of the Willamette, many Chinook salmon rapidly migrate through Columbia and Snake River reservoirs at temperatures 421°C (stream-type, Keefer et al, 2004a;ocean-type, Goniea et al, 2006).…”

The importance of parentage in assessing temperature effects on fish early life history: a review of the experimental literature

“…For example, not one of the salmonid adult thermal holding studies was conducted using a wild parent population. Many wild Pacific salmon stocks are facing warming, often stressful, thermal regimes during reproductive migration and incubation (MacDonald 2000; Mote et al 2003;Angilletta et al 2008;Strange 2010). For many of these populations, it would be useful to simulate these extreme temperature experiences in a controlled experimental setting to explore the potential for gamete quality or offspring traits to be affected.…”

Quantifying Temperature Effects on Fall Chinook Salmon

“…During these times, adults sought thermal refuge in tributaries, which averaged 2-7°C cooler than the mainstem. Migration was also inhibited in the Klamath River basin at temperatures from 21.8 to 24.0°C (mean = 22.9°C) (Strange 2010). Strange proposed daily average or weekly maximum temperatures of 23°C or weekly average of 22°C as upper thermal limits for migration.…”