For as long as there have been fish farms in this province, there have been fish escaping from cages into the wild. Conservationists have suspected those escapees breed with native fish, changing their DNA.

Now they say they have proof.

One of the largest escapes in Newfoundland happened in 2013, when more than 20,000 salmon got away from a farm in Hermitage Bay. That incident inspired DFO scientists to study the genetic material of fish in salmon rivers on the island’s south coast.

“We looked at 19 rivers in the first year and hybrids were detected in 18 of those rivers,” said lead researcher, biologist Brendan Wringe.

More than 1/4 of river salmon are hybrids

“We weren’t surprised to find hybrids. We were surprised to find as many hybrids as we did and to find them as widely spread as we did. In total of the 17-hundred odd fish we sampled, about 27 per cent showed farmed origin. So they may have been hybrids or, more worryingly, feral fish. So that would be fish where both parents were of direct farm descent.”

Wringe said salmon interbreeding worries scientists because hybrid offspring may not be as able to survive as well as wild fish.