Monitoring the white sturgeon comeback

Longtime residents of Lincoln County may remember fishing for white sturgeon in the Kootenai River prior to construction of Libby Dam.  Even in the late 1960s and early 1970s sturgeon were occasionally caught by anglers downstream of Kootenai Falls, including the 96-pound state record caught in 1968.  

By the late 1970s, only five white sturgeon were estimated to reside in the Montana portion of the Kootenai River and harvest of sturgeon was closed in 1979.  In the 20 years following construction of Libby Dam, captures of white sturgeon in Montana became increasingly rare.  

In 1994, the Kootenai River white sturgeon population in Idaho and Montana was listed as endangered under the Endangered Species Act due to insufficient levels of juvenile recruitment needed to sustain the wild population.  Factors including land-use changes, construction of dikes, loss of floodplain habitats, and construction and operation of Libby Dam have likely all contributed to the decline of white sturgeon in the Kootenai River.  

In the early 1990s, the Kootenai Tribe of Idaho began an experimental hatchery program for white sturgeon in an effort to prevent extinction of the species and to supplement low levels of natural reproduction occurring in the wild.  Since the first experimental spawning efforts, nearly 250,000 juvenile white sturgeon (1-2 years old) and more than 3 million free embryos (3-4 days old) have been released into the Kootenai River and Kootenay Lake. Of those sturgeon, Montana has received roughly 15,000 juvenile sturgeon and 200,000 free embryos.  Survival of juvenile sturgeon from the hatchery averages about 50 percent in the first year at large and 84 percent each year after that. 

So, if 1 million juvenile sturgeon are stocked into the Kootenai River, roughly 5,000 to 10,000 will make it to age 30.  

Hatchery-raised sturgeon can be identified using two methods.  The first is a lateral scute removal pattern.  Scutes are the bony, scale like plates on the sides of sturgeon.  Scutes are removed using a unique pattern each year on one or both sides of each hatchery sturgeon.  The second way to identify hatchery sturgeon involves PIT tags. PIT tags are small microchips inserted under the skin with a hypodermic needle. PIT tags must be scanned with specialized readers but they allow growth, survival, and movement data to be collected for individual white sturgeon.  

To date, most hatchery-raised white sturgeon have been released in Idaho and British Columbia where intensive monitoring programs exist. The programs assess basic population characteristics such as population numbers, movement, growth and spawning activity. Until recently, monitoring of white sturgeon in Montana has not received the same level of attention.  

From the early 1980s until about 2005, information on white sturgeon in Montana consisted of very limited sampling efforts that were discontinued due to low-catch rates and rare angler catches or sightings.  In the last 5 to 10 years, reports of white sturgeon in Montana have become more frequent. Are white sturgeon making a comeback in Montana?  Montana Fish, Wildlife & Parks staff is currently trying to answer that question.

In 2009, with funding from Bonneville Power Administration, Montana Fish, Wildlife & Parks began a five-year pilot effort to reassess the status of Kootenai River white sturgeon in Montana.  Initial sampling between 2009 and 2011 produced 13 sturgeon over 41 days of sampling.  However, despite being limited to six days of sampling in 2012 because of high flows from Libby Dam, Montana Fish, Wildlife & Parks personnel captured 32 sturgeon. During the past four years, 44 of the 45 sturgeon captured were from the hatcheries in Idaho and British Columbia. The final sturgeon captured in 2012 did not have any scutes removed, contained no PIT tags, and may have been the result of natural reproduction in the Kootenai River.  

White sturgeon captured in Montana during the past four years ranged from 20 to 46 inches long and from 5 to 22 years old at the time of capture. Our current estimate of white sturgeon in Montana is about 100 fish, which is only a small proportion of the total number of wild and hatchery fish residing in the Kootenai River and Kootenay Lake.  

While the increasing trend in catch rates and population numbers in Montana is promising, the species is not out of the woods.  The wild population of white sturgeon continues to struggle and the first juvenile sturgeon stocked from hatcheries in the early 1990s will not mature until between 2015 and 2030.  

It remains to be seen whether the hatchery sturgeon will be able to successfully reproduce at levels high enough to sustain the population but the next 15 years should be very interesting. The hope is that the juvenile sturgeon will spawn throughout the Kootenai River and consistent natural recruitment will be restored.  

If that happens, anglers may once again be able pursue and harvest a white sturgeon in the Kootenai River.   

(Ryan Sylvester  can be reached at 406 293-4161 ext. 203 or rsylvester@mt.gov.)