The use of insect meal — particularly black soldier fly larvae (BSFL, Hermetia illucens) — as a fishmeal replacement in aquaculture feeds is growing rapidly. This development has complex welfare implications: it reduces pressure on wild fish stocks used for fishmeal, but raises questions about insect welfare and requires careful nutritional assessment for farmed fish.
Conventional salmon and trout feeds rely heavily on wild-caught fishmeal and fish oil from industrial fisheries. This creates welfare and sustainability concerns — wild fish are caught and processed in ways that raise welfare questions, and the fisheries carry sustainability risks. Insect meal from BSFL offers a protein source that can be produced locally, using organic waste as a substrate, with a much lower land and water footprint.
BSFL meal is nutritionally suitable for partial replacement of fishmeal in salmon, trout, and other salmonid diets. Studies indicate that up to 25-50% fishmeal replacement is achievable without negative impacts on fish growth, health, or welfare, particularly when combined with appropriate amino acid supplementation. Higher replacement levels require careful formulation. Full replacement is not yet demonstrated for all life stages.
Whether insects are sentient — whether they experience pain and distress in morally significant ways — is genuinely uncertain. The Birch et al. (2021) review found the evidence for insect sentience weaker than for decapod crustaceans, but acknowledged that the absence of evidence is not evidence of absence. The scale of insect production for feed is enormous — potentially hundreds of billions of individuals — meaning even a low probability of sentience represents a significant expected welfare consideration. Some researchers advocate applying the precautionary principle and studying insect welfare as a priority.
BSFL used for fishmeal are typically killed by blanching (hot water or steam) or by freezing. Research on the most humane killing method for insects is limited but emerging. Rapid methods (very high temperature) may be preferable to slower methods (chilling), though this is contested. This is an area of active research with significant welfare implications given the production scale.