🐛 Farmed Eel Welfare Science 2025

Overview

Eels are among the most enigmatic and threatened fish globally. European eel (Anguilla anguilla) populations have collapsed by 90%+ since the 1970s; Japanese eel (A. japonica) is critically endangered. Yet eel aquaculture is enormous in Asia — Japan, China, and Taiwan produce hundreds of thousands of tonnes annually — driven by demand for unagi (grilled eel) in Japanese cuisine. Paradoxically, all farmed eels are initially wild-caught as glass eels (juveniles), intensifying pressure on already-depleted wild populations.

Welfare in Eel Aquaculture

Eel welfare in aquaculture involves several distinct challenges:

• Extreme density: Eel farms operate at very high densities (100-200 kg/m³) in indoor tanks; behavioral research is limited but chronic crowding stress is likely
• Aggressive behavior: Eels are aggressive and cannibalistic at high density, causing bite injuries to fins and body
• Water quality: High waste production requires intensive filtration; ammonia spikes cause distress
• Transport: Eels are transported alive in low-water, high-density conditions over long distances; mortality is significant
• Killing methods: Eels are often killed by asphyxiation in cold water or salt, causing prolonged distress

Conservation-Welfare Link

The European eel crisis creates an unusual welfare-conservation alignment. Protecting wild eel populations requires reducing glass eel capture, which also reduces the welfare harm of wild capture and aquaculture. Restoring migration routes (dam removal) and reducing mortality in industrial water intakes benefits both wild eel welfare and population recovery. The EU Eel Regulation attempts to manage recovery, though implementation has been inadequate.