USFWS Works with Partners to Find Solutions

BY AARON JUBAR

The river was slightly turbid from rain the day before, but the high-powered spotlights provided enough visibility that we could still see the river bottom, numerous suckers, salmon, and logs, lots and lots of logs. This stretch of the Manistee River contains countless half-submerged trees, silent and enormous sentinels left behind from a bygone logging era.

We kept a watchful eye on the many underwater hazards throughout our patrol, but had our sights set on much different and more elusive quarry. Suddenly, a voice cried out, “There’s one!” Swimming just above the gravel and struggling against the current was an ancient and revered fish, a lake sturgeon. Only this sturgeon wasn’t one of the gentle behemoths that most are familiar with… this was a juvenile only six inches long. “Keep the lights on it while I swing the boat around!” shouted Rob Elliott, our captain for the evening. Elliott, a fish biologist with the U.S. Fish and Wildlife Service (Service), is experienced in nighttime surveys for juvenile lake sturgeon.

As Elliott began maneuvering the boat into position, I dropped my spotlight and grabbed a specially designed dip net.  Just before the sturgeon was out of reach, I leaned far over the side, made a desperate swipe, and got lucky. The crew erupted with hoots and hollers that echoed across the banks of the dark river. A bystander might have thought we’d stumbled upon sunken treasure. And in a sense, they’d have been right. This young sturgeon is indeed a treasure.

The Manistee River is home to a small but genetically unique population of lake sturgeon, one of just a dozen or so similar populations that live in tributaries to Lake Michigan. This long-lived fish species spends most of its adult life in bays and coastal waters of the Great Lakes. It is estimated that 15-50 adult sturgeon return to the Manistee River each year to spawn, and the offspring typically spend their first summer in the river. After feeding and growing for several months, these juvenile lake sturgeon migrate downstream to Manistee Lake and eventually into Lake Michigan where they live for 15-25 years before returning as mature adults to spawn in their natal river.

“Sturgeon have been returning to the Manistee River for thousands of years, but after being nearly wiped out during the heavy logging and commercial fishing period in the late 1800s, their numbers have been slow to recover” explains Elliott.  “Due to slow growth and low abundance, the survival of these young, wild sturgeon is very important to the future growth of this population.”

The Manistee River is also home to the sea lamprey, another ancient, yet devastating, fish lurking in the stream bottom. But whereas the lake sturgeon is endemic to the Great Lakes ecosystem, the invasive and parasitic sea lamprey has been wreaking havoc on Great Lakes fish populations since the 1930’s. With the Manistee River harboring an estimated 1.3 million larvae, it is one of the largest sea lamprey producing streams in Lake Michigan.

The Service works as an agent of the Great Lakes Fishery Commission to control sea lamprey populations in all five Great Lakes. The primary means of controlling sea lamprey larvae is through the use of lampricides-specialized pesticides designed to kill lampreys. The Manistee River is treated by the Service every three years with lampricides to eliminate sea lamprey larvae before they can metamorphose into the parasitic life stage and enter Lake Michigan where they feed for 18 months and destroy valuable fish species. A single sea lamprey is estimated to destroy 40 lbs of Great Lakes fish during its parasitic phase.

The coordinated effort to collect and retain juvenile lake sturgeon from the Manistee River during these late August nights was no coincidence. Lake sturgeon juveniles can be sensitive to lampricides, especially in streams that have high alkalinities. The Manistee River is highly alkaline but must be treated. Currently, the abundance of sea lampreys in Lake Michigan is at a 20-year low and allowing the Manistee River to go untreated would quickly lead to a resurgence of sea lampreys in the basin.

The Service has partnered with the Little River Band of Ottawa Indians (LRBOI) and Michigan Department of Natural Resources (MDNR) to explore ways to maintain effective sea lamprey control while minimizing impacts to young lake sturgeon. The nighttime sturgeon “round-up” is a means to protect the fish by removing them from the river prior to lampricide exposure.

Our boat’s tally was six juvenile lake sturgeon, more than double our previous night’s catch. The other two survey boats fared even better, combining for 31 sturgeon. We set off for the LRBOI lake sturgeon streamside rearing facility (SRF), the temporary home for these small fish until the stream was treated and then free of lampricide. The SRF has been used by the LRBOI since 2004 to raise collected eggs and young lake sturgeon in a protected environment for eventual release back into the Manistee River when they are larger and less vulnerable to predation.

Each juvenile lake sturgeon was measured, weighed, implanted with a unique tag, and a small snip collected from one of its fins. The fin snips would be used for genetic analysis to determine parentage of each individual and estimate the number of adults contributing to this year’s cohort. The internal tags, detectable through the use of a special wand, would be used to identify each fish in future years. After a few moments of careful handling, the young sturgeon were placed in one of several holding tanks within the SRF. The tanks separated the fish by sampling stations within the river, allowing each fish to be returned to the general vicinity in which it was caught following the lamprey treatment.

These majestic fish are sacred to the LRBOI tribal members, with cultural significance dating back for millennia. “Each fall the LRBOI holds a sturgeon release ceremony on the banks of the Manistee River. The ceremony helps achieve our management goal of restoring harmony and connectivity between the sturgeon and the community,” stated Corey Jerome, LRBOI Fisheries Biologist. Lake sturgeon are also significant to the residents of Michigan and other Great Lakes states. Dr. Marty Holtgren, MDNR lake sturgeon expert, explains, “Sturgeon were historically an important member of the Great Lakes ecosystem and connected to the people inhabiting it. This collaboration is aimed to continue rehabilitating the species and re-establish our natural heritage with this fish”. The lake sturgeon – sea lamprey issue on the Manistee River is a great example of partners working together to achieve a common goal. For now, this collaborative effort represents a creative way in which to conserve lake sturgeon in alkaline systems like the Manistee River that are treated with lampricides on a fixed schedule.

By week’s end, the crews would combine to collect 117 juvenile lake sturgeon. After a highly effective lampricide treatment in which hundreds of thousands of lampreys were eradicated, the young sturgeon were released back into the stream. With any luck, many of them will reach maturity and return to the Manistee in a few decades to spawn.  And the LRBOI community will be there to welcome them.

Sea lamprey control is carried out in all five Great Lakes by the U.S. Fish and Wildlife Service and the Department of Fisheries and Oceans, Canada. Funding for the sea lamprey control program is provided by the Great Lakes Fishery Commission.

Aaron Jubar is a Fish Biologist with US Fish and Wildlife Service’s Sea Lamprey Control Program at Ludington, Michigan.

https://www.fws.gov/midwest/Ludington/