Last month, when state biologists released the results of an annual index monitoring bull trout spawning beds in the Flathead River basin, their conclusion that the native population is stable and secure illuminated an ongoing dispute over how to monitor and manage the threatened species.
With dueling missions of promoting a “secure” versus a “recovered” species, state and federal agencies differ on the management goals for native bull trout and clash over the metric employed to gauge the future of the species’ viability.
Federal biologists monitoring bull trout recovery in Flathead Lake say the state’s annual assessment is overly optimistic given the bigger picture of recovering a sensitive species, particularly in the context of a warming climate and increased predation by invasive lake trout.
But biologists with Montana Fish, Wildlife and Parks maintain that the recent survey, which the agency has conducted annually for 33 years, shows the bull trout population is well above the secure minimum threshold, with market improvements since the population collapsed in the early 1990s under increased pressure from lake trout in Flathead Lake.
The 2013 FWP survey documented 500 bull trout redds, or spawning nests, in the North and Middle Forks of the Flathead River, which falls below the numbers of the early 1980s but hovers above the 1990s figures. Those bull trout numbers were so low they prompted federal officials to designate the native fish a threatened species under the Endangered Species Act.
FWP Spokesperson John Fraley said the estimate of 500 redds is 66 percent above the minimum secure level of 300 redds, a threshold established in 2002 under the Flathead Lake and River Fisheries Co-Management Plan. The count is also better than the 15-year average of 434 redds.
In 2002, the Confederated Salish and Kootenai Tribes and the FWP, who share fisheries management authority on Flathead Lake, adopted the co-management plan with the goal of increasing the abundance of native bull trout and westslope cutthroat trout.
Under the Endangered Species Act, the recovery criteria call for a return of the bull trout population in Flathead Lake to a mid-1980s level, which hovered around 900 redds basinwide.
Wade Fredenberg, a fish biologist with the U.S. Fish and Wildlife Service who is charged with recovering the species, said the co-management plan, which expired in 2010, is outmoded and inadequate as a conservation threshold.
“The current level of 500, which (FWP) touts as being 60 percent above secure, is really only about 55 percent of our recovery level,” he said.
To promote genetic diversity, Fredenberg said the objective is to maintain about 30 redds per stream, but some of the redd counts in the Flathead tributaries are in the single digits. “In 2012, only four of 10 met that standard,” he said.
Biologists assume an average of three fish spawn in each redd, so 500 redds equates to about 1,500 bull trout in the two river systems.
“I would equate Montana’s ‘secure’ levels as being closer to a border between threatened status and endangered, whereas the FWS’ ‘recovery’ level is more like the border between threatened and delisted,” Fredenberg said.
Aquatics ecologist Clint Muhlfeld, whose research at the U.S. Geological Survey’s Glacier National Park field station helps guide conservation and management programs, said the plan does not pass muster as a roadmap to conservation and recovery, especially because it does not pay adequate consideration to individual subpopulations.
The definition of a “secure level,” he said, must consider the health of each individual spawning tributary.
“It’s like lights on a Christmas tree — the more lights that go off makes the tree less brilliant,” he said. “In the Flathead, several lights have blinked out in recent years and several more are flickering, threatening the persistence of the bull trout population.”
Since implementation of the co-management plan, Muhlfeld said bull trout abundance has declined in several streams and some populations are now functionally extinct.
“The best available scientific information suggests that bull trout inhabiting the upper Flathead Lake and River system are not secure, with several local populations and Glacier National Park bull trout core areas at high risk of extirpation in the foreseeable future,” he said.
“Based on this evidence, 300 redds is not a secure level.”