Research by biologists with FWP have learned the source of two illegally introduced walleye that were caught in a gill net in Swan Lake back in 2015.

"We have some biologists here who are doing amazing work, including Sam Bourret, who specifically studied some of the intricacies of the walleye's otoliths, which are these geo-chemical tracers within the ear bones of fish and those tracers help identify where those fish were originally from," said FWP Region One Public Information Officer Dillon Tabish. "Sam, through his research, was able to discover that those walleye were in fact from lake Helena."

Authorities are hoping that the source of the fish may help in locating the culprits that took them to Swan Lake, a larger than average reward is available to encourage information.

"There is a reward available up to $35,000," Tabish said. "The State of Montana offers rewards of $15,000 for any illegal fish introduction, but for this specific incident Trout Unlimited has pledged a reward up to $20,000 for a tip that could result in the conviction of whoever was responsible for introducing those walleye to Swan Lake."

Tabish says the fact that the fish were born in Helena Lake is a good sign, it shows that the walleye had not been reproducing in Swan Lake. Illegal fish introductions happen surprisingly frequently, there have been over 600 confirmed illegal fish introductions in 250 Montana water bodies.