If you were to catch a lake trout or a bull trout in Montana waters, would you know which is which?  A new app may be able to help.

“It’s harder than most people think to identify fish correctly,” said Tom McMahon, a professor in the Fish and Wildlife Ecology and Management Program within the Department of Ecology in the College of Letters and Science at Montana State University.  “There are a lot of fish that kind of look alike.”

In 1971, long before the university became known as Trout U, MSU published “Fishes of Montana” by C.J.D. Brown, and the field guide has since remained a vital resource for identifying species in the field. It includes 80  varieties of fish in the state, with histories, distribution maps and characteristics, but in nearly half a century, the book has never been updated.

For years, McMahon and ecology department colleagues Alexander Zale and Christopher Guy, leader and assistant leader of the U.S. Geological Survey Montana Cooperative Fishery Research Unit,bandied the idea of a new edition of the book. However, a different opportunity presented itself when Guy met Whitney Tilt, a Bozeman conservationist whose previous collaborations with Matt Lavin, a professor in the Department of Plant Sciences and Plant Pathology in MSU’s College of Agriculture, led to two field identification smartphone apps, Montana Grasses and Flora of the Yellowstone Region.

Rather than revise and reprint “Fishes of Montana,” the book has been given a 21st century update with the release of its namesake Fishes of Montana app. The app, now available for Android and iOSdevices, includes information on 90 native and introduced species. The app is free to download, funded by a $10,000 grant  from retailer Patagonia that was awarded to the Department of Ecology to promote the restoration of native fish populations as part of the Trout and Cold Water Fisheries Initiative.

The app includes a comprehensive species list for quick reference, which includes the common and scientific names. It tells whether the fish is native or introduced, threatened or a game fish. Fishes of Montana also contains a glossary, a map of major drainages in Montana, diagrams on fish anatomy and links to more resources.

To develop the app, the MSU team enlisted Tilt as project manager and Katie Gibson of the Bozeman company MountainWorks as the developer. They then called on Montana Fish Wildlife and Parks, partners in the Cooperative Fishery Research Unit, to provide expertise. 

“This partnership is really neat,” Guy said. “It allows us to bring it all together and develop a product with the best resources available in the state.”

Printed guides have been important for those doing field work in places without an internet connection. The new app is equally portable; Fishes of Montana does not require cellular coverage or a wireless connection for basic identification. The app’s information draws from both books and FWP’s online field guide, FishMT.

“The app is now the most current resource for contemporary taxonomy,” said David Schmetterling, a fisheries research coordinator with FWP who was part of the development team.

It also relies on the knowledge base of the fisheries community, FWP and the university.

“The faculty at Montana State University are the best ichthyologists we have in the state,” Schmetterling said. “For generations, MSU has been looked at for those skills and that knowledge.” 

Making correct identifications is important. FWP’s fishing regulations center around being able to identify the species. For example, Guy said lake trout are considered at risk of becoming endangered due to declining populations in their native waters, but invasive when introduced elsewhere. Bull trout are listed as a threatened species by the U.S. Fish and Wildlife Service. Daily limits, or fishing bans, reflect these designations.

“Lake trout we want gone in many waters,” Guy said. “Bull trout must stay. But they look similar.”

Lake trout have more spots than bull trout and their tail fins have deeper forks, according to Fishes of Montana. Bull trout’s spots are a pale yellow on their back and red or orange going down the side. Lake trout have light gray spots, never red or orange.

McMahon teaches an ichthyology class each spring. His students learn to identify fish species using a dichotomous key, which gives a couplet, or pair, of statements and asks the user to pick one of the two choices leading them to another couplet. Those choices become increasingly specific until a match is found. Students learn the key, but often don’t rely on it in the field.

The broader approach of Fishes of Montana “might actually fit better,” Zale said.

The app invites users to identify fish species through a polyclave key, which uses a process of elimination based on observed characteristics. Choose the location within the state, the shape of the tail or if an adipose fin is present. If you don’t know what an adipose fin is, a graphic with an arrow points to its location (between the main back fin and the tail). The ­app then provides a list of fish meeting the specified characteristics.

“The polyclavel approach is user friendly,” Tilt said. “It encourages the user to explore and not worry about making a mistake.”

McMahon plans on using the app in his next ichthyology class.

Aside from students and scientists, the app is useful for anglers of all ages. According to Schmetterling, one FWP employee took a beta version on a Missouri River fishing trip and his 10- and 13-year-old children were able to identify the six or seven different species.

“The unique thing about this app is it serves many different purposes to different audiences,” he said.

Fishes of Montana users could also lend insight into changes in distribution or the presence of fish species, including aquatic invasive species. For this reason, the app has information on 10 species the State of Montana hopes never to see in Montana waters, such as the snakehead, round goby and bighead carp. If a user is unable to identify a species or wants to share information, the app contains a direct email link to Schmetterling inviting the user to attach a photo.

“What I especially like about the way Fishes of Montana was developed is it promotes communication from people using the app to us,” he said.