The boats of both countries take fish returning to spawn in the rivers of either.

ECONOMIST: Canada

The Angling Trust said it was disappointed after none of 72 fish electronically tagged negotiated the barrage to migrate up river to spawn.

BBC: Fears over Tees Barrage impact on fish

Coral-reef fish tend to grow slowly, take many years to reach reproductive age, and then spawn in only a few localised sites.

ECONOMIST: What price coral?