‘Fish Detective’ Gains Attention for Pioneering Research

Montana FWP biologist publishes study on illegal fish introductions in distinguished journal

By Tristan Scott
Sam Bourret, fisheries biologist with Montana Fish, Wildlife and Parks. Courtesy FWP

A local Montana Fish, Wildlife and Parks biologist who identified an innovative forensic sleuthing technique to investigate illegal fish introductions is having his research published in an international peer-reviewed scientific journal.

Sam Bourret, a fisheries biologist based out of FWP’s Region 1 office in Kalispell, was the lead author of a manuscript titled, “Using forensic geochemistry via fish otoliths to investigate an illegal fish introduction.”

If that sounds like a mouthful, consider it in terms of a piscatorial crime scene investigation involving fish detectives instead of traditional CSI investigators.

The forensic findings will be featured in the November edition of the Canadian Journal of Fisheries and Aquatic Sciences, which is published by the NRC Research Press, the largest scientific publisher in Canada with 24 journals distributed to over 125 countries. Niall G. Clancy, a graduate student at Utah State University, co-authored the paper with Bourret.

The research is based on a study of the first suspected illegal introduction of walleye in Swan Lake in October of 2015. Using forensic geochemistry via fish otoliths, or their inner ear bones, Bourret was able to trace the origin of the non-native walleye.

The research paid off.

The otoliths, which are the calcium carbonate structure in the inner ear bones of fish and contain unique geochemical identifying tracers, revealed that the walleye matched the geochemical signature of walleye from Lake Helena in central Montana, about 10 miles from Helena.

The research also identified that the walleye were introduced to Swan Lake sometime in the spring of 2015 and most likely have not established a population in Swan Lake.

Bourret’s study marked the first use of otolith geochemistry as a forensic tool on a large scale. The information provides an important clue into the ongoing investigation of who illegally introduced the walleye. It also has far-reaching implications that could help inform invasive species management and monitoring.

“Our results highlight the utility of otolith geochemistry as a forensic tool, which has led to another study of a suspected illegal Northern Pike introduction in Lake Mary Ronan,” Bourret said.

Like a tree’s concentric growth rings, a small bone within a fish’s ear reveals a history of its growth. The bone also contains a record of its migration pathways — a kind of geochemical diary of its life.

“We hope that by understanding more about illegal introductions and getting closer to making an arrest, our study will help curb future illegal fish introductions by notifying the public that FWP is serious about stopping the problem,” Bourret said.

By publishing a manuscript in the NRC Research Press, Bourret’s innovative research is now being shared with the world’s scientific community as an important tool from a distinguished source.

Bourret graduated from the University of Idaho with a Master of Science degree in fisheries science in 2013. He joined FWP as a fisheries biologist in 2015.

“FWP biologists around the state provided otoliths used to identify the waterbody source of the introduced walleye. This type of coordination and information exchange is key to addressing broad scale management challenges like illegal fish introductions,” Matt Boyer, FWP Region 1 Science Program Supervisor, said.

A mere two walleye might not sound like a threat, but the fish breed prolifically and feed voraciously. If a population takes hold in Swan Lake, the threat to native bull trout, a threatened species, would be significant.

Illegal introductions can have significantly negative impacts on lakes and rivers. They can often lead to fewer recreational fishing opportunities, as well as collapsing ecosystems and altered food webs. Walleye are highly predacious and could impact the native bull trout population, as well as the kokanee salmon fishery in Swan Lake.

The danger posed in Swan Lake is particularly troublesome as the pristine water body has been identified as a refuge for cold-water species like bull trout, which, if climate-model predictions prove correct, could face the loss of habitat over time.

The state department’s concern is shared by the fishing community and conservation organizations, which stepped up to bolster the investigation by offering a monetary incentive.

A reward up to $35,250 is available for information leading to the conviction of whomever is responsible for the illegal introduction. The state of Montana offers rewards up to $15,250 for information about illegal fish introductions. Montana Trout Unlimited has pledged a reward of $20,000 for a tip that results in the conviction of the individual or individuals responsible for illegally introducing the walleye into Swan Lake.

Anyone with possible information on who introduced walleye into Swan Lake is encouraged to call 1-800-TIP MONT. Callers do not need to identify themselves and may be eligible for the cash reward.