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The Mystery of the Sicklefin Chub

Sicklefin Chub photo.

Sicklefin Chub

by Dave Hagengruber, Montana Fish, Wildlife & Parks

Grant Grisak is a Fisheries Biologist who works for Montana Fish, Wildlife & Parks. There are many different duties that come along with the job of a biologist, including setting fishing seasons and regulations, helping to improve the habitat of fish in lakes and streams, and monitoring the health and numbers of fish in the areas which the biologists manage. But Grant never imagined part of his job would involve solving a mystery: the mystery of the Sicklefin Chub.

Sicklefin Chubs are small fish found in the lower Missouri River in Montana. They are also found in the Missouri River in other states. No one knew very much about them, but fisheries biologists sometimes caught them in their nets as they tried to catch other fish. The first person to ever record catching a sicklefin chub in Montana was a biologist who caught one from the Missouri River in 1980.

In the early 1990's, people began to get worried that some of the fish populations in the Missouri River might be in trouble. Since no one had ever paid much attention to sicklefin chubs before, biologists wanted to see if they could catch more of them in their nets. When they tried netting in the places they had caught sicklefins in the past, they did not catch many. In fact, the fishing was so bad that in 200 tries with their nets, only 4 chubs were caught.

Grant Grisak had just started working for Montana Fish, Wildlife and Parks about that same time. He wanted to go back to school and spend time studying more about fish, and he heard about the problems with the sicklefin chubs. Grant decided that he would combine his last years of college with a research project to see if he could learn why the sicklefin chubs seemed to be disappearing.

He spent lots of time on the Missouri River, looking for the fish. But his luck at finding the sicklefins seemed to be no better than anyone else's. He caught only 5 chubs in many, many tries during his first summer.

The work Grant was doing on the Missouri River was difficult, and sometimes even dangerous. He and the members of his team would put on waders, climb in the river, and then pull seines, or long nets through the water and try and trap the fish inside. With the strong currents and deep water of the river, it was hard work. They were frustrated because they could not find the sicklefin chubs in the places they were found just a few years earlier.

They decided to try looking in deeper water, places that they could not take their nets if they pulled the nets by hand. Instead, they attached the nets to a jet boat, and pulled them through the water with the boat. But pulling nets with a jet boat was also difficult, and very dangerous. The bottom of the Missouri River is covered with huge old trees, and large boulders. If the nets got caught on one of these rocks or stumps, the heavy currents of the river might be strong enough to pull the boat underwater.

Grant began to call other biologists in other states to see what ideas they might have to find the fish. He talked to dozens of other biologists, from all across the United States. They had lots of ideas for him to try, but the time and money Grant had for his research project were just about gone. His team decided to try looking for sicklefins in a different type of river habitat, with a different method of pulling the nets. They didn't know it, but their luck was about to change!

Grant decided to try looking in places in the river with both deep water and a fast current. Because this fast current made the work especially dangerous, they decided to tie the nets to the front of the boat. That way, if the seines became entangled with the bottom, the current would not pull the back end of the boat down into the river.

On their first attempt, they pulled up a net full of sicklefin chubs! In one try, they had caught more chubs than anyone ever imagined. Each pull of the nets brought up more chubs, along with a variety of other fish that had never been captured in the river before. Tiny, newly hatched shovelnose sturgeon, endangered pallid sturgeon, and paddlefish all were captured in their nets. No one had ever been able to find where these species went when they were first hatched, but Grant and his team had solved that mystery too.

Most importantly though, they caught sicklefin chubs. Based on the information they gathered, Grant and other biologists were able to demonstrate that the population of these fish in the river was not in danger.

This all happened almost ten years ago. Today in Montana, sicklefin chubs have not been listed as a threatened or endangered species. Instead, they are known as a Species of Special Concern, which means that biologists and fisheries managers are carefully watching their population to make sure it remains stable and healthy.

Although Grant never dreamed that working as a fisheries biologist would involve so much detective work, he was glad he was able to learn some good news about the population of sicklefin chubs. He also learned an important lesson: to never draw conclusions without looking at all of the evidence, and most importantly, to never give up without trying your best.

Sicklefin Chubs

Sicklefin Chubs in Montana grow to a maximum size of about four inches. They like the turbid, or murky areas of the lower Missouri River, where they live with a variety of other species of fish. Since the visibility is so limited in the river, sicklefins have a very unique adaptation to help them find their food. They have a great sense of smell, and actually have taste buds on the edges of some of their fins!

Although they are old enough to spawn, or lay their eggs over rock and gravel bottom when they are two years old, most sicklefins do not spawn until their third year of life, and very few of them ever live past their fourth birthday.

Sicklefin chubs are important to humans because they are good indicators of the health of the river ecosystem where they live. They also serve as a valuable food source for other fish and animals who share the river with them.