Use of Electroshock for Euthanizing and Immobilizing Adult Spring Chinook Salmon in a Hatchery

Abstract

This study evaluated the use of electroshock as an alternative to traditional techniques for immobilizing and euthanizing hatchery fish. We used a commercially available electroanesthesia unit at the U.S. Fish and Wildlife Service's Carson National Fish Hatchery (Carson, Washington) to euthanize adult spring Chinook salmon Oncorhynchus tshawytscha and to sort and collect gametes of fish at maturation. During euthanization by electroshock, the response of each fish was observed, muscular and vertebral hemorrhaging was quantified, and electrical settings were optimized accordingly. During gamete collection, fish were either electroshocked or exposed to tricaine methanesulfonate (MS-222); hemorrhaging, egg viability, egg size and quantity, and resultant fry quality were examined for each treatment group. Electroshocked fish had a higher likelihood of injury during gamete collection than did fish exposed to MS-222. On average, each electroshocked fish had less than two hemorrhages on both fillets examined. The size of each hemorrhage was less than 0.10% of the fillet surface. Fecundity and egg and fry quality were not affected by either immobilization method. Electroshock was a viable and efficient means of euthanizing adult spring Chinook salmon or sorting the fish and collecting their gametes. However, equipment settings must be optimized based on site-specific (e.g., water conductivity) and species-specific (e.g., fish size and seasonal state of maturation) factors.

Impact of electric fishing on egg survival of whitefish, Coregonus lavaretus

“…According to the literature (Lamarque 1990; Beaumont et al Survival rates from three laboratory treatment groups representing different distance groups plotted against effective voltage assuming that treated (anesthetised) fish experienced similar effective voltages than measured (dead) fish in the respective distance group (anode distances: 10 cm (1.02 V cm À1 ), 40 cm (0.62 V V cm À1 ) and 80 cm (0.48 V V cm À1 )) and control group (0.00 V cm À1 ). The findings for O. tshawytscha may illustrate this issue: values from four studies (Roach 1996;Tipping & Gilhuly 1996;Barnes et al 1999;Zydlewski et al 2008) vary from À66 to 1670% changes in mortality. Surveys for northern pike Esox lucius Linnaeus and razorback sucker Xyrauchen texanus (Abbott) reported less pronounced increases in egg mortality (not more than 2.3%) than that (6.7%) observed in the more sensitive salmonids (Walker et al 1994;Muth & Ruppert 1996).…”

“…2002), salmoniform species are more influenced by electrofishing than others; this also seems to be the case for their gametes. In some studies, higher egg mortalities were found for electrofishing with voltages between 250 and 350 V (Roach 1996;Barnes et al 1999) than for electric immobilising with high voltage up to 550 V (Tipping & Gilhuly 1996;Zydlewski et al 2008). The general problem in comparing the existing data is that electrofishing techniques used may be modified to suit to the environmental conditions to be successful and there are no standardised methods for the investigation of the effect of electricity on ripe fish eggs.…”

Electrofishing of Landlocked Fall Chinook Salmon Broodstock Negatively Impacts Egg Survival

“…Likewise, no negative effects on egg survival were observed when hatchery Chinook Salmon were immobilized by electric shock for gamete collection when equipment settings were properly optimized for location‐specific water quality parameters and species‐specific factors (Zydlewski et al. ).…”

“…; Zydlewski et al. ). Because electrofishing can cause both internal and external damage to the fish being collected (Snyder ), particularly salmonids (Oberlercher and Wanzenbock ), its use as a fisheries management tool may be limited when dealing with sensitive juveniles or imperiled fish (Miranda and Kidwell ).…”

Bruising patterns in commercially harvested yellowtail flounder (Limanda ferruginea)

“…Grunwald and Richards, 2006;Lefèvre et al, 2008;Johnsen et al, 2011;Rotabakk et al, 2011;Olsen et al, 2013). Spectroscopy and/or image analysis software has been used to characterize discolouration (and other defects, such as gaping and nematodes) in herring Clupea harengus (Roth et al, 2007), Atlantic cod Gadus morhua (Heia et al, 2007;Sivertsen et al, 2011;Olsen et al, 2014) and various salmon species (Zydlewski et al, 2008;Erikson et al, 2010;Balaban et al, 2011). The benefits of image analysis include objectivity, as well as the ability to create a reliable baseline from which to compare later research to detect the impact of changes to processing techniques.…”