Just as with other farmed vertebrates such as cattle, sheep and poultry, the humane slaughter of fish requires that fish are handled carefully and effectively stunned (causing immediate insensibility) prior to being bled out.
Unfortunately, traditional methods of killing fish do not meet these requirements. Farmed fish are still commonly killed by asphyxiation (suffocation by taking them out of water), exposure to carbon dioxide, exposure to very low temperatures or bleeding without stunning. These procedures take several minutes to induce insensibility and cannot be regarded as humane.
Electrical and percussive stunning methods for fish are now becoming more common. These include water-bath stunning systems where fish pass through electrified water to stun them, and percussive stunning of fish using automated flow-through systems where fish remain in water until the point of stunning. These systems remove the need for pre-slaughter handling of fish and allow fish to be effectively stunned prior to being bled out. RSPCA Australia encourages fish farming operations to utilise these technologies to ensure that fish are slaughtered humanely.
RSPCA Australia is grateful to the Humane Slaughter Association for information presented in this article.