Freshwater crayfish (kōura) are an important food source for many fish, but they also take advantage of an unexpected opportunity—they feed on dead fish, including predators. In Aotearoa New Zealand, kōura are a treasured taonga species for Māori, yet they face heavy predation from introduced fish like catfish. Fish Futures’ Calum MacNeil, Finnbar Lee, Ian Kusabs and Robin Holmes research tested whether kōura prefer the carcasses of native predators, such as longfin eels, or introduced ones like catfish.
The results? Kōura aren’t picky—they readily leave their hiding places to feed on any dead fish, whether eel, catfish, or even marine species. This means that when catfish die in lakes where they’ve invaded, kōura will scavenge them. Thousands of catfish are culled each year in eradication programmes, and these carcasses are currently wasted. We suggest they could instead be used as food for kōura, especially in conservation-focused aquaculture, helping offset the harm catfish cause to native crayfish populations.