Current research and guidelines for euthanasia in laboratory fish with a focus on fathead minnows

Area of Science:

• Animal Welfare Science
• Aquatic Toxicology
• Laboratory Animal Science

Background:

• Humane anesthesia and euthanasia are critical in laboratory fish research.
• Previous reviews indicate a need for standardized, well-documented protocols.
• The fathead minnow (Pimephales promelas) is a common model organism in ecotoxicology.

Purpose of the Study:

• To review and analyze methods for humane anesthesia and euthanasia of laboratory fish, focusing on the fathead minnow.
• To assess the quality of reporting for these methods in scientific literature from 2004-2021.
• To identify research gaps and provide recommendations for improving animal welfare.

Main Methods:

• A systematic literature survey of 333 scientific studies published between 2004 and 2021.
• Analysis of reported anesthesia and euthanasia techniques across different fish life stages.
• Evaluation of the completeness of method descriptions in published research.

Main Results:

• Many studies lack adequate detail on anesthesia and euthanasia procedures, especially for larval fathead minnows.
• A 20% increase in described euthanasia methods was observed over two decades.
• Younger fish, including larval and juvenile fathead minnows, may require higher anesthetic concentrations than adults.

Conclusions:

• Standardized, detailed reporting of anesthesia and euthanasia methods is essential for scientific reproducibility and animal welfare.
• A two-step euthanasia protocol (anesthetic immersion followed by spinal severance/exsanguination) is recommended.
• Further research is needed on rapid cooling efficacy, depth of anesthesia assessment, and humane euthanasia for larval/juvenile fish.