Validation of reflex indicators for measuring vitality and predicting the delayed mortality of wild coho salmon bycatch released from fishing gears

Abstract

Summary1. Effective management of fish and wildlife populations benefits from an understanding of the effects of stressors on individual physiology. While physiological knowledge can provide a mechanistic understanding of organismal responses, its applied utility is limited because it cannot easily be used by stakeholders. 2. Reflex action mortality predictors (RAMP) is a method that involves checking for the presence or absence of natural animal reflexes to generate a condition (RAMP) score in response to stressors and to predict fate. The method has previously been validated with fishes in artificial laboratoryand field-based holding studies as a responsive measure of fisheries capture stress and a predictor of delayed mortality, but has not been evaluated in the wild. 3. We used radio telemetry to monitor migration success of 50 endangered coho salmon Oncorhynchus kisutch following incidental capture in an aboriginal beach seine fishery in the lower Fraser River (Canada). RAMP was used to measure the condition of fish at release and to predict migration success following capture. Biopsy of an additional 43 coho profiled physiological condition at time of release. 4. Individuals with greater reflex impairment (higher RAMP scores) at release experienced significantly higher rates of migration failure. RAMP scores were also significantly correlated with fishery handling time. Plasma variables showed that captured coho had experienced physiological stress characteristic of exhaustive exercise and hypoxia, with significantly elevated cortisol and lactate values for fish entangled longer in fishing gear. 5. Synthesis and applications. This is the first validation of RAMP in a wild setting. Based on our findings, fishers could use the method and make adjustments in fishing behaviour in real-time to improve fish condition and reduce the mortality of bycatch, and conservation practitioners could monitor animal condition and identify problems that deserve management attention. RAMP is an easy, rapid and inexpensive approach to predicting mortality and measuring vitality and performed better than traditional physiological tools that cannot easily be used by stakeholders.

Conservation physiology in practice: how physiological knowledge has improved our ability to sustainably manage Pacific salmon during up-river migration

“…A more recent radio-tracking study has shown that endangered interior Fraser coho salmon released from a beach seine are more likely to reach their natal spawning areas with a better RAMP score (i.e. fewer impaired reflexes; [36]). Presumably by integrating underlying physiological systems, greater reflex impairment reflects a state further from homeostasis, from which a complete recovery is less likely and latent mortality is more likely.…”

Behavioural and reflex responses of mottled mojarra Eucinostomus lefroyi (Gerreidae) to cold shock exposure

“…Conversely, declines of 6 and 8°C caused rapid equilibrium loss and significant reflex impairment, particularly at 8°C below ambient temperature. Equilibrium loss is a common result of cold shock exposure in fish, and is an indication of physiological stress that may lead to mortality (Griffith 1978, Hyvärinen et al 2004, Donaldson et al 2008, Davis 2010, Raby et al 2012. Loss of ability to swim upright also greatly reduces the capacity of fish to move into deeper water to escape further cold exposure (in the case of storm-induced perturbation of shallow waters) or avoid predators, further increasing the probability of mortality.…”

“…A total of 5 RAMP indices were used: tail grab, body flex, head complex, vestibular−ocular response (VOR), and equilibrium. These metrics were chosen because they are strong indicators of vitality in other fish species in the context of fisheries-related stress (Raby et al 2012, Brownscombe et al 2013, as well as cold shock (Szekeres et al 2014). Tail grab was assessed by grabbing the fish's tail by hand, and was considered impaired if the fish did not immediately attempt to swim away.…”

Post-tagging behaviour and habitat use in shortnose sturgeon measured with high-frequency accelerometer and PSATs

“…This is the first step in developing a tagging system that can be used to test post-release behaviour and potentially physiological response to capture, handling and release (e.g. [39][40][41]). Therefore, we tagged five shortnose sturgeons with high-frequency accelerometers mounted on PSATs that recorded environmental variables over a 2-day period.…”

“…High VeDBA during tag-load-related movements, indicated by high roll angles in the smallest individual, likely contributed to additional energy expenditure. The extended resting period and increased energy expenditure due to postrelease stress could contribute to increased vulnerability to other stressors, fishing recapture or death [30,31,40,41,59,[62][63][64][65].…”