Successful recovery of the physiological status of coho salmon on board a commercial gillnet vessel by means of a newly designed revival box

Abstract

Successful application of fish-revival techniques in commercial fishing prior to release of nontarget species requires clear evidence that recovery devices do indeed improve physiological status and minimize postcapture delayed mortality. This study provides such evidence for a newly designed recovery box (Fraser box) that assisted gill ventilation. Immediately after capture by gillnet, adult coho salmon (Oncorhynchus kisutch) were in a state of severe metabolic exhaustion and stress, based on a comprehensive analysis of plasma and muscle tissue. However, when placed in a Fraser recovery box for 1-2 h, both lethargic and vigorous fish showed significant metabolic recovery and their ability to swim was also quickly restored. An emphatic demonstration of the benefit of the Fraser box was the successful revival of >90% of fish that appeared dead at capture. Furthermore, postcapture delayed mortality was only 2.3% after a 24-h observation period. Therefore, in the context of commercial salmon gillnet fishing, revival of nontarget coho salmon in a Fraser box, in combination with a soak time (total time the gillnet is in the water) £ 70 min and careful fish handling to minimize physical trauma, could improve physiological status, restore swimming ability, and markedly reduce postcapture delayed mortality. Farrell et al.Résumé : Pour que l'application de techniques de réanimation de poissons non-ciblés avant leur rejet à l'eau lors de pêches commerciales soit un succès, il faut s'assurer que les moyens de rétablissement améliorent de fait la condition physiologique et minimisent la mortalité différée après la capture. Notre étude fournit une telle assurance dans le cas de l'utilisation d'une enceinte de rétablissement récemment conçue (la boîte de Fraser) qui favorise la ventilation des branchies. Immédiatement après leur capture au filet maillant, les Saumons coho adultes (Oncorhynchus kisutch) sont en état d'épuisement métabolique et de stress, comme l'indique une analyse détaillée du plasma et du tissu musculaire. Cependant, après 1-2 h dans la boîte de rétablissement de Fraser, tant les poissons léthargiques que les poissons vigoureux font preuve d'un rétablissement métabolique significatif et retrouvent rapidement leur capacité de nage. Une démonstration significative de l'efficacité de la boîte de Fraser est que plus de 90 % des poissons qui semblaient morts à la capture s'y sont rétablis avec succès. De plus, la mortalité différée après la capture était de seulement 2,3 % après une période d'observation de 24 h. Dans le cas de la pêche commerciale au saumon à l'aide de filets maillants, la réanimation des Saumons coho non ciblés par la pêche, combinée à un temps de mouillage des filets de £ 70 min et une manutention soignée des poissons de façon à minimiser les traumatismes physiques, peut donc améliorer la condition physiologique, rétablir la capacité de nage et réduire de façon marquée la mortalité différée.[Traduit par la Rédaction] 1946

Oxygen uptake in Pacific salmon Oncorhynchus spp.: when ecology and physiology meet

“…fontinalis (Milligan et al , ; Kieffer et al , ), and can accelerate recovery in wild O . kisutch after capture with commercial fishing gear (Farrell et al , ). The mechanisms that accelerate recovery are poorly understood, but may involve cortisol dynamics or oxygen delivery improvements (Milligan et al , ; Kieffer et al , ).…”

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

“…Farrell et al [28] found that non-target wild coho salmon (Oncorhynchus kisutch) captured by troll, seine and gill net showed signs of severe metabolic exhaustion at the time of capture, raising concerns over the likelihood of post-release survival. To address this concern, methods for facilitating and expediting physiological recovery were tested [28] and refined [29,30]. The idea of promoting recovery from fisheries capture stemmed from results of Milligan et al [31], who provided evidence for accelerated metabolic recovery from exhaustive exercise in the laboratory of hatchery-reared rainbow trout (Oncorhynchus mykiss) when they were recovered in flowing water while swimming at constant velocity (i.e.…”

“…This application of the results of the Milligan et al [31] study was expanded to the commercial troll fishery where Farrell et al [30] found that placing fish in a cage/net pen towed alongside the moving vessel resulted in rapid physiological recovery and no mortality during the 24 h assessment period. Facilitated recovery using a revival box, called the Fraser Box after the commercial fisher who constructed the first prototypes, successfully promoted physiological recovery, rapidly restoring swimming ability in 1-2 h, and resulted in high post-release survival, even for fish that appeared moribund at the time of gill net capture [29]. The survival benefit of the Fraser Box has resulted in these recovery boxes being implemented in marine commercial fisheries for releasing coho salmon.…”

“…Identifying between-sector similarities is useful for developing general management principles that could simplify policy development and harvest allocations [37], but represents a research area that is challenging to address owing to inherent differences among capture methods, locations, environmental conditions and even among stocks [34]. The work by Farrell et al [29,30] provides a robust technique for promoting physiological recovery and survival, and represents a relevant example of science being implemented into management regimes. Our work on coho bycatch in freshwater fills an important knowledge gap for a species of conservation concern, and tests a novel method for monitoring physiological impairment at the whole-animal level, through RAMP [36].…”

Coho salmon haematological, metabolic and acid‐base changes during exercise and recovery in sea water

“…Lee et al . (2003 a ) measured critical swimming velocities and exercise‐associated oxygen consumption rates in ocean‐ranched and transgenic coho salmon and Farrell et al . (2001 a , b ) measured the physiological consequences of troll‐capture and vessel‐based recovery in wild coho salmon.…”