Anglers on the Kettle River system have reported a handful of invasive smallmouth bass since Aug 25 when fishing opened on the river, according to provincial biologists.
The presence of the predatory fish has not yet been confirmed but scientists have been sampling the river trying to find any sign of either smallmouth or largemouth bass, which threaten rainbow trout.
"[Bass] eat everything and anything including rainbow trout eggs and fry," said Tara White, the province's senior fish biologist in the Okanagan region.
Smallmouth bass have never been confirmed in the Kettle River system above Cascade Falls, but, below the falls, where the river heads south into the United States, bass are a native species.
However, largemouth bass were previously confirmed in the Canadian part of the river just east of Grand Forks.
Most likely illegally introduced
"It's unlikely that they would be able to migrate the falls, so the highest possibility is that they were illegally introduced or moved by the public," said White.
She warned that illegally introducing fish species in British Columbian waters can come at a hefty cost.
Fines for allowing an aquatic invasive species to escape for a first time offender range from from $2,500 to a maximum of $250,000 and up to two years in jail.
Anyone who sees, catches or otherwise comes across a bass is asked to keep the fish in their freezer and contact the Penticton Fish and Wildlife branch and staff will retrieve the sample.
White added that GPS coordinates and photographic evidence are extremely helpful for officials looking to confirm the presence of an invasive species.
Trout recently rebounded
The Kettle River is a destination for anglers looking to target rainbow trout in the Okanagan because there are few places to do so in Region 8.
"We don't have many river systems in the Okanagan that you're able to fly fish on. It is a beautiful system," said White.
White said the rainbow trout population only recently rebounded after many years of low stocks and mandatory fishing closures.
Trout numbers have been good recently, she said, but the fishery is still catch and release only as warming river temperatures and low stream flows still threaten stocks, according to White.