Non-native knifefish are causing problems for fishermen in the Philippines' largest lake.
The fish, measuring up to 50cm/20" are reported to be multiplying in Laguna Lake on the edge of Manila, where they are displacing the native species.
They were reportedly being bred locally for the aquarium trade. It's not known for certain how they came to be in the lake but it seems likely they were intentionally released there.
Asis Perez, head of the Philippines' Bureau of Fisheries and Aquatic Resources, said: "It is carnivorous. It will compete with our existing natural fish. We have yet to get a full appreciation of the damage caused by this fish."
Fishermen's groups have complained that their catches of native fish are shrinking, and because few people want to buy the knife fish to eat, their income is threatened.
The suckermouth catfish — known locally as the "janitor fish"— was also introduced by ornamental fish breeders, where it has since displaced native species and damaged nets.
"This could be like the janitor fish. They were both introduced in the Philippines as ornamental fish. They could have escaped or they could have been intentionally freed," said Perez.
Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.