Short‐term Physiological Response Profiles of Tagged Migrating Adult Sockeye Salmon: A Comparison of Gastric Insertion and External Tagging Methods

Abstract

A variety of electronic tag types are routinely applied to fish to better understand migration biology. However, tagging procedures have the potential to affect the postrelease behaviour and survival of tagged individuals. In this study, wild adult Sockeye Salmon Oncorhynchus nerka from the Harrison River, British Columbia, were radio‐tagged by gastric insertion or external attachment techniques immediately after capture to understand the short‐term physiological response to these two tagging methods. Plasma cortisol, glucose, lactate, sodium, and potassium levels, as well as white muscle lactate and glycogen concentrations, were measured in samples obtained from fish upon capture (0 h) as well as 1 or 4 h after the tagging treatment. The effects of key biological variables, such as sex and proximity to spawn, on the physiological response to the tagging events were also evaluated. Tagging occurred during two distinct time periods representing fish of different maturation states and durations of freshwater residency. Overall, the physiological response to the tagging scenarios was characteristic of the disturbance associated with exhaustive exercise. There were no significant differences detected in the response profiles following gastric or external tagging procedures. This was despite procedural differences such as stomach perforations observed in 68% of the gastric insertions in the late sampling period, and external attachments taking three times longer (43 s) than gastric insertion (15 s). Moreover, the tagged fish showed similar response profiles to control fish that were handled but not tagged. These results suggest that the capture and handling associated with a tagging event induced physiological disturbance, and that the addition of a quick tagging procedure appeared to be nonadditive over the 4‐h assessment period. Sex and proximity to spawn had significant main and interaction effects on some of the physiological response variables, indicating that biological context is important for interpreting physiological assessments in experiments that manipulate exercise and stress responses in migrating adult Pacific salmon.

Metabolic constraints and individual variation shape the trade‐off between physiological recovery and anti‐predator responses in adult sockeye salmon

“…Nonetheless, simple tank transfers can cause increases in f H above basal levels (Laitinen & Valtonen, 1994). Furthermore, stress effects associated with handling, at the level of circulatory metrics, have been shown to mask treatment‐level outcomes in migrating sockeye salmon (Dick et al ., 2018). Together, these factors may have contributed to a relatively “high” peak f H in control fish.…”

Biotic and abiotic determinants of the ascent behaviour of adult Atlantic salmon transiting passable waterfalls

“…We suggest that the environmental conditions that they will encounter must factor into the decision, with internal tags preferable where salmon are expected to encounter high flows (Thorstad et al, ), but with the warning that new surgical incisions may not heal well for salmon negotiating a river with waterfalls such as Numedalslågen (as shown by two recaptured fish in this study). Gastric tagging was not evaluated here but is a rapid method of nonsurgically implanting a tag; however, gastric tags may damage the stomach of the fish (Dick et al, ), and the long‐term effects are unknown, potentially making them unsuitable for iteroparous species.…”

Non-Lethal Sampling Supports Integrative Movement Research in Freshwater Fish

“…An important property of physiological samples is that they are a ‘snapshot’ of the fish’s physiological status at that time, however acute markers can be sensitive to handling stress during tagging/manipulations ( Lower et al, 2005 ; Stoot et al, 2014 ; Dick et al, 2018 ; Lawrence et al, 2018 ), and are sometimes limited to larger fishes where samples can be obtained ( Lawrence et al, 2020 ). Biopsies are typically taken when the fish is captured and restrained, and is often conducted in concert with tagging or other sampling events (e.g., Miller et al, 2009 ; Raby et al, 2012 ).…”

“…While such biopsies are typically quick (typically a few minutes to perform; Raby et al, 2012 ; Henderson et al, 2016 ), anaesthesia can be used for longer sampling workups ( Bøe et al, 2020 ). Importantly, the process of capture, handling, and sampling can impart stress on the animal which may affect post-release mortality and predation ( Raby et al, 2014 ; Hoyle et al, 2015 ), post-release behaviours ( Hoolihan et al, 2011 ), and alter the physiological status of the sample itself ( Dick et al, 2018 ; Lawrence et al, 2018 ). Therefore, sampling should always be conducted expediently and in a manner that minimizes harm and stress to the fish itself.…”