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The Future of Blue Suckers
NorthWestern Energy and our partner agencies are studying why juvenile blue suckers seem to be missing from the population.
It’s likely that some of the blue sucker fish found in Montana’s Missouri River could be nearly 70 years old. However, young blue suckers seem to be missing.
“In the last 23 years, we have not observed any young blue suckers,” said Grant Grisak, Biologist with NorthWestern Energy.
Blue suckers are considered a species of special concern in Montana and are specifically listed in our fisheries monitoring plan, part of the federal license that allows us to operate dams on the Missouri and Madison rivers. Blue suckers are found in the Missouri River, downstream of Morony Dam, our most-downstream dam on the Missouri.
For more than 20 years, biologists with NorthWestern Energy, Montana Fish, Wildlife & Parks, and other agencies have been monitoring these fish through a variety of techniques designed to sample a broad range of habitats and sizes from newly hatched fish to adults. We’ve surveyed the blue sucker population through electrofishing, trammel netting, seining and trawling. We’ve also surgically implanted radio transmitters in adult fish to follow their movements throughout the year.
“We look at their behavior and try to make some determinations about what those fish are responding to during the winter time, during the summer or during their spawning season,” Grant said. “We’re building a picture of what their behavior is like.”
However, through all of those monitoring techniques, biologists are not finding any juvenile blue suckers. That could be because the population is so low that there aren’t enough adult fish to get together and spawn, Grant said, or the conditions in the river aren’t allowing young fish to survive.
“We don’t know where this bottleneck might be,” Grant said. “That’s the question we’re trying to answer.”
NorthWestern Energy and Fish, Wildlife & Parks are now using a fish aging technique that was used to determine the age of several bigmouth netting, seining and trawling. We’ve also surgically implanted radio transmitters in adult fish to follow their movements throughout the year.
“Blue suckers are believed to be a very old fish, just like the bigmouth buffalo,” Grant said.
To get a better understanding of age structure of the bigmouth buffalo, biologists in Minnesota used radio isotope aging looking at the boney structure of the fish. Through their studies, they determined bigmouth buffalo in the study area ranged in age from 3 to 92 years old. They also found that 82% of the fish population was greater than 75 years old.
NorthWestern and FWP began a similar study this spring to determine the age of blue suckers. Grant hopes this data can help biologists see which years were the most successful for blue sucker spawning. Then, they can study the river conditions from those years – what were the river flows? And the water temperature?
NorthWestern Energy biologists are studying the rare blue sucker in the Missouri River to help increase the population.
“If we could determine the years fish were born, we could associate those years with a particular environmental event,” Grant explained.
The major flood-control dams in the Missouri River watershed were constructed almost 70 years ago – Canyon Ferry Dam in 1954 and Tiber Dam in 1956.
“We believe some of these fish were born before some of the major flood-control dams were put on the river,” Grant said.
Grant believes the age data on blue suckers may lead to a similar recovery plan as pallid sturgeon. The pallid sturgeon population dropped so low that it required moving the few remaining wild fish into hatcheries. The nearly 4,900 pallid sturgeon that are now in this same reach of river are the result of fish raised in hatcheries and released into the river. NorthWestern has played a significant role in those recovery efforts and our funding has been vital for the project.
“We’ve done that with a very high degree of success,” Grant said. “We think that could be a very similar path for the future of blue suckers.”
