Non‐direct homing behaviours by adult Chinook salmon in a large, multi‐stock river system

Abstract

Two non-direct homing behaviours, overshoot of natal tributaries and temporary non-natal tributary use, were evaluated for 5150 radio-tagged spring-summer Chinook salmon Oncorhynchus tshawytscha from 40 populations in the large Columbia River system. Over 7 years, 2-44% (mean ¼ 15%) of individuals within each group temporarily entered presumed non-natal tributaries. In addition, many Chinook salmon from lower river tributaries initially travelled 3 to >250 km upstream in the main-stem river beyond confluences with presumed natal tributaries before returning to the natal sites ('overshoot'). Both overshoot and temporary tributary use behaviours declined exponentially with increasing distance from the natal tributary. Nondirect homing also increased later in the season as water temperatures rose and was associated with hatchery origin in some cases. The behaviours may reflect a mix of active searching for olfactory cues from natal sites, behavioural thermoregulation and orientation challenges in a large-river migration corridor transformed by dams and reservoirs. While anadromous salmonid homing is generally accurate and precise, these results indicate that route finding can be non-direct, potentially increasing energetic costs and harvest risks during migration.

What is “fallback”?: metrics needed to assess telemetry tag effects on anadromous fish behavior

“…Seventh, the occurrence of short distance forays (\2 km) also should be reported, as this indicates active swimming behavior. The timing of these movements may indicate exploration (Keefer et al, 2008), the drive to spawn (Acolas et al, 2004), or a reaction to the environment (Dodson et al, 1972). If possible, these post-tagging movements should be linked to known information about success of spawning.…”

“…Often the downstream movements of upstream migrating salmon are described as a purposeful behavior in response to the environment, obstacles, or a mechanism of homing . These complex behaviors include overshooting of natal systems (Naughton et al, 2006), exploratory movements (Keefer et al, 2008), seeking alternate routes, waiting for appropriate conditions (Thorstad et al, 2005;Holbrook et al, 2009), disorientation in certain hydraulic conditions (Naughton et al, 2006), being swept over dams (Matter & Sandford, 2003), or varying sensitivity in distinct migratory phases (Makinen et al, 2000;Jokikokko, 2002). Aberrant movement in salmonids has not been explicitly related to ''fallback'' or tag effect (Young et al, 2006); for example, when radio tags were used to examine the effect of catch-and-release on adult Atlantic salmon (Salmo salar), uncharacteristic up and downstream movements of radiotagged fish observed post-release were attributed to angling (Thorstad et al, 2003).…”

Within-stream release-site fidelity of steelhead trout from Lake Erie hatchery stocks

“…As such, we can address the issue of straying, but must define strays as individuals not from these hatcheries; that is, individuals who were found in Conneaut Creek, but were not Ohio-or Pennsylvania-stocked fish. We found that 13.8% of adult (non-yearling) steelhead trout collected in Conneaut Creek were known strays (stocked by Michigan and New York), which is higher than the 2.5% of knownorigin salmonids that were considered permanent strays in the Columbia and Snake Rivers (Keefer et al, 2008). However, this is not unprecedented for populations of stocked fish.…”

Population-specific escapement of Columbia River fall Chinook salmon: Tradeoffs among estimation techniques

“…Radiotelemetry data also allowed estimation of salmon fallback at dams. If unmeasured, fish that fall back and do not reascend can produce overestimates of upstream escapement (Dauble and Mueller, 2000;Boggs et al, 2004) and underestimates of escapement to downstream sites (Keefer et al, 2008). The PITtag detection data currently collected at dams cannot account for most fallback fish that do not reascend fishways .…”