Project aims to restore sturgeon
CEDAR RIVER — Collaborative efforts are being made in Cedar River to help restore the sturgeon population in Lake Michigan. Members of the Michigan Department of Natural Resources (MDNR) and the US Fish and Wildlife Service have been caring for 164 sturgeon, which currently vary in length from four to five inches, since the first week of May. Located at a streamside rearing facility along the Cedar River, which is funded in part by the Fox River Green Bay Natural Resource Trustee Council, the sturgeons’ caretakers are gearing up for their eventual release at the end of August.
This year marks an operational return for the Cedar River facility after taking a two-year hiatus due to COVID-19.
“[Sturgeon] are a threatened species in Michigan and there are a lot of efforts around the Great Lakes to restore them to their historical abundance,” John Bauman, fisheries biologist at the MDNR’s Escanaba Field Station, said.
The Cedar River feeds directly into Green Bay, the largest fresh water estuary in the world. While the bay used to hold scores of sturgeon, the waters now contain less than 1 percent of the fish’s historical abundance. Due to high predation rates in their early life stages, thanks to the threat of rusty crawfish and rock bass, it is incredibly difficult for sturgeon eggs, larvae, and fry to survive after spawning season. While a single female sturgeon can lay anywhere from 500,000 to 1 million eggs, very few will survive.
The sturgeon that do survive, however, burrow themselves into the stream substrate to hide from predators and feed off their yolk sacs in peace. Eventually, the sturgeon emerge from the substrate and travel downstream during the evening and early morning hours. It is at this time that Bauman and others collect the drifting sturgeon larvae and introduce them to the streamside rearing facility.
“A streamside facility is a little bit different than a traditional hatchery in that it uses the water that we want [the sturgeon] to imprint to for the entire rearing process,” Bauman said. “That way they hopefully develop some sensory cues to tell them that [the Cedar River] is home.”
Sturgeon are a highly migratory species. After wandering hundreds of miles away from their river of origin, sturgeon will return to the same river when it is time to reproduce. However, sturgeon are unique in that they do not mature until they are between 10 and 20 years old, sometimes even older if they are female. Therefore, since the Cedar River streamside rearing facility has only been operating since 2007, just two of their sturgeon have returned to the area. An additional two were detected in the Peshtigo River as well.
“The goal is to release up to 750 to 1,000 fish annually. Sometimes we get 990 to a little over 1,000 and sometimes we get 100 to 200,” Bauman said. “So that is four fish total out of around 8,000 that have been released. But it is still early and we can’t make any conclusion on what we have got so far.”
The mechanical intricacies of the streamside facility are straightforward. An intake pump located alongside the Cedar River transports fresh water straight from the source to a head tank. From the head tank, the water is lead into several smaller tanks within the trailer-like facility using the force of gravity. Of all the water that is funneled towards the facility, only 10 percent is being used. The rest gets returned to the river.
“The fish are exposed to a lot of those natural fluctuations in temperature, which we think is going to be good for their survival,” Bauman said. “If the fish have genes that allow them to deal with a high temperature or large fluctuations in temperature, those genes are going to be expressed because they are raised in this facility and being exposed to that.”
Of the 900 sturgeon larvae that were collected from the Peshtigo River during the first week of May this year, 164 remain. When first brought back to the facility, the sturgeon were being fed brine shrimp, a tiny aquatic crustacean. For the first couple weeks of their lives, the sturgeon ate 30 to 40 percent of their body weight in brine shrimp.
While the current survival rate of the sturgeon rests just below 20 percent, Devin Rath, a student at Lake Superior State University who has been employed to help care for the sturgeon, is impressed by their growth progress.
“The [sturgeon] we do have are a nice size, some of them are four to five inches,” Rath said. “You would think they are really prickly, but they are not.”
Jennifer Johnson of the U.S. Fish and Wildlife Service has been tending to the sturgeon as well. In addition to cleaning and feeding, Johnson has been measuring fish growth, in both length and weight, twice a week to ensure they are getting the right amount of food. According to Johnson, a majority of the fish have doubled in size in just a month. Because of this, the sturgeon have graduated from brine shrimp to blood worms for their daily feeding.
“[Johnson] and I did some math … and if a baby human grew as fast as a sturgeon did, a human would be 19 feet tall on their first birthday,” Bauman said.
Johnson’s favorite fish, which has been named “Stumpy,” is the smallest of sturgeon being held at the facility. In addition to the smaller size, Stumpy has only one point on his tail in comparison to the standard two.
Once the sturgeon reach roughly six inches, which is projected to be in three to four weeks, they will be tagged with a Passive Integrative Transponder (PIT). These unique tags, which have a 100 year lifespan, allow Bauman and others to track the fish. Because the PIT tags have a cooper coil, every time they pass through a magnetic field the copper is charged and emits a detectable frequency.
Sturgeon reintroduction is extremely important to local waters. In addition to being a good indicator of water and habitat quality, sturgeon are also valuable nutrient transporters. After consuming zebra mussels, clams, and other invertebrates, sturgeon will convert all of that energy into egg mass or milt. Due to the migratory nature of the species, the fish will deposit the egg mass or milt hundreds of miles away, where it will either become sturgeon egg or food for other critters.
“Zebra mussels have done a lot to take a lot of those nutrients out of the water and reduce some of the productivity in Lake Michigan,” Bauman said. “We have somewhat of a reduced capacity to build fish biomass now because of what zebra mussels have done to the water. Sturgeon will hopefully help offset that.”
For local anglers, the legality of hook and line fishing for sturgeon is dependent on the body of water that is being fished. More information on the various sturgeon seasons and legal fishing waters, visit michigan.gov/dnr.
“[Sturgeon] are massive. There is no other species in the Great Lakes that competes with that from an angler’s perspective,” Bauman said. “There are some opportunities around the state for catch and immediate release where it is legal to target them, but you have to release them as soon as possible.”