Managing wild trout

POWELL — After migrating to the North Fork of the Shoshone River and more than a dozen major tributaries to spawn in the spring and early-summer months, many of the highly migratory rainbow and Yellowstone cutthroat trout return to Buffalo Bill Reservoir.

This wild population of trout, which have survived without stocking efforts from Wyoming Game and Fish Department fisheries biologists, is the pride of the Cody Region.

But while the population isn’t being supplemented, it is getting help.

Regulations issued by the Fish Commissioner in 1884 (prior to the Game and Fish Department) on this fishery include a seasonal closure from April 1 to June 30 of the lower portion of the North Fork and on a small portion of the reservoir from April 1 to July 14.

A four-year study led by Cody Region Fisheries Supervisor Sam Hochhalter is now near completion; the only remaining aspect is the collection of social data from anglers who fish the upper Shoshone River, from Yellowstone National Park to the reservoir. The study could lead to changes, including an increased number of days anglers can fish in closed areas.

“As fisheries managers, we want to take a comprehensive approach to managing this unique fishery,” Hochhalter said in an interoffice report. “This means collecting the biological data necessary to understand the dynamics of the fish population and the social data from anglers on their preferences for future fishing opportunities, which will be done in part through an email survey this fall.”

The study team set up the study to track the seasonal movement patterns of those adult trout in the North Fork of the Shoshone River and Buffalo Bill Reservoir.

“It’s not rocket science,” Hochhalter said in an interview with the Tribune. “The vast majority of the adult trout in that system spend the winter months in Buffalo Bill Reservoir, and each spring, it varies year to year, they start trickling into the North Fork as early as March.”

Oftentimes, they found it tends to be the latter half of April and first half of May when “big waves” of spawning trout are moving out of Buffalo Bill and entering the North Fork of the Shoshone River, he said.

In April and May their goal was to capture and tag 2,000 individual rainbow, cutthroat or rainbow cutthroat hybrid trout. Each individual fish received two tags, each with unique numbers so the team could track individual fish throughout the four years of the study.

In the end, the study resulted in identifying more than 8,500 uniquely tagged individual trout in the four years.

The study found that regardless of the time of year, the number of trout within the closed section of the North Fork was approximately two times greater than the number of trout upstream of the closure, and trout abundance was by far the highest in the closed section during the closed time period. The study found angler harvest to be fairly high for a wild trout population.

Across four years of the study, approximately half of the annual harvest occurred in the river portion, and half in the reservoir portion.

“While annual harvest and catch-and-release related mortality was high, it is sustainable,” Hochhalter said.

Results indicate the dates of the fishing closure on the North Fork of the Shoshone River, part of the oldest seasonal closures in Wyoming’s history spanning the entire state, could be shortened, allowing anglers more days to fish the closed section, but daily bag limits and potential terminal tackle restrictions would be necessary to prevent increased mortality, Hochhalter said.

“The bottom line is the current regulations provide a sustainable fishery, as would a host of alternative regulations that wouldn’t increase harvest or catch-and-release mortality,” Hochhalter said.

While the closures could be shortened, they are not in a position to completely remove the closure.

“A closure, in some fashion, is necessary to provide those trout with adequate time to enter the tributaries and spawn. But we absolutely could shorten the closure in terms of the number of days each spring it’s closed,” he said.

The study showed quite clearly that the shortened closure can only be beneficial if there is a reduction in harvest, or if the department has regulations that do not also increase harvest. It makes sense from what the department knows about the population, that some form of regulation continues, he said.

“I think that’s why it’s continued to exist over the last 140 years. But there’s a lot of other regulations that are available that would lead to sustainable management of this trout population,” he said.

Now the department will ask anglers, in the form of a survey, to chime in to help make the decision; do they want more days to fish, but each day take home fewer trout?

Either way, they could leave well enough alone and feel confident that they’re sustainably managing the long term health of the wild trout population, or make changes, allowing for more fishing days and smaller limits.

The current limits on the population are three harvested trout, no more than two being cutthroats and only one fish over 18 inches.

Fisheries biologists will be working with the Wyoming Survey and Analysis Center out of Laramie, who will actually administer the survey.

All the questions will be specific to the current regulations and potential future regulations for the North Fork and Buffalo Bill.

“We want to provide this information to anglers and let them weigh in as we prepare for the next regulation cycle in early 2025,” he said.

To learn more about this fishery and the results of this study, the public is invited to an informational meeting from 6-8 p.m. on Sept. 11 at Shreve Lodge at Buffalo Bill State Park.