Friends of the Upper Mississippi

Genoa NFH staff collected female washboard mussels last October in the Mississippi River near Prairie du Chien. The washboard population there had spawned several weeks prior to our collection visit, and we were able to collect female mussels who brooding mature larvae (glochidia) in their gills. Washboard females don’t hold their viable glochidia for a particularly long time, so the females were brought straight back to the lab and kept in clean, translucent, flow-through tanks so we could watch for the natural release of their glochidia.

Scuba diving in the UMR to collect gravid female mussels, including the washboard mussels that were used for juvenile production in early 2022. Photo credit: Erica Rasmussen/USFWS.

mucus-y cobwebs with embedded glochidia. Photo credit: Beth Glidewell/USFWS.

Within a few days of laboratory observation (and slightly warmer temperatures in the mussel building vs the Mississippi River in October), several females released wispy, cobweb-like mucus nets containing viable glochidia. In the river, these webs and strands drift up into the current from the female, ready to ‘catch’ unsuspecting fish. When a fish swims through the web, the glochidia in the mucus strands brush by the fish, and snap shut when they encounter fish tissue. Some of these glochidia will attach to the gills of the correct host fish (channel catfish, black bullhead, and green sunfish) and successfully transform into juvenile mussels, though many will fail to attach to any fish, and others will attach to a non-host and be sloughed as the fish’s immune system protects the fish.

While glochidia in the wild have a relatively low likelihood of attaching to the correct fish type, this step of the mussel reproductive cycle is something we can greatly improve in the laboratory- collected glochidia are checked for viability and added to a tub of known host fish -channel catfish- greatly increasing successful attachment and transformation of the glochidia into juvenile mussels. Host fish that have glochidia encysted on the gills are kept in the mussel building over winter at natural surface water temperatures, these cold conditions keep the glochidia from developing too quickly so they remain encapsulated in the fish’s gills until the spring. As temperatures naturally warm, or the fish are moved to heated culture systems, the glochidia continue their metamorphosis into juvenile mussels. When fully developed, they break free from the fish’s gill and drop into the water, settling on the bottom of the culture tank where they can be collected and moved to juvenile mussel culture systems.

The first juvenile washboard produced from last October’s production were collected in February. As juveniles are collected, they’re placed in sediment trays for grow-out. These sediment trays- boxes with clean sediment, aerated well water, and an algae/diatom mussel food mixture- are monitored and fed daily to keep the juvenile mussels happy and healthy. Some of these produced juveniles have been sent to partner agencies for research uses, and others will be cultured this spring and summer (and beyond) for population augmentation in local rivers. By: Beth Glidewell

A juvenile washboard with visible shell growth along the ventral margin. Photo credit: Beth Glidewell/USFWS.

Megan adding glochidia to tubs of catfish, greatly increasing the likelihood of connection between an individual glochidium and a target host fish. Photo credit: Beth Glidewell/USFWS

As you may have seen in previous editions of Genoa News and Notes, the coldwater production building on the north end of the hatchery grounds (hence, Coldwater North) received a major makeover last year. What was once gravel and fiberglass is now manicured concrete, and a once sleepy artesian well can now double its output with the aid of a booster pump. What all this means is our Coaster Brook Trout program now has a new permanent home. We are now able to raise two year classes side by side in the same building and the fish can remain there throughout their time at the hatchery. We fully put the new setup to the test in March, cranking up the pump and moving nearly 13,000 7” trout into the raceways to go along with their 1” roommates currently living in circular tanks. Zach Kumlin has been busy at work reestablishing our alarm system and troubleshooting any bugs in the system. This building will help us achieve the Service’s goal of producing quality Coaster Brook Trout for Lake Superior and tribal waters for years to come.
By: Nick Bloomfield

Brook Trout in a net being weighed, concrete raceway, Photo: Erica Rasmussen/USFWS.

Genoa National Fish Hatchery was contacted by the Wisconsin Department of Natural Resources
with a request to supply Northern Pike and Walleye eggs for Lake Mills State Fish Hatchery, WI.
Northern Pike on the Mississippi River start spawning in early April just before ice out and for a few
weeks after the ice has cleared. Staff from the Genoa National Fish Hatchery set fyke nets in the
backwaters of the Mississippi River where the water is shallower and warmer during this time of year
to collect enough adults for spawning. Once enough adults were collected the eggs were fertilized
and WI DNR staff met GNFH staff to pick up the eggs and return them to Lake Mills Hatchery. Lake
Mills Fish Hatchery will rear these fish at the hatchery for stocking into state waterbodies in support of
sport fishing opportunities for anglers.

By: Orey Eckes

Hoop net in water and pike eggs being measured. Photo: USFWS

Some exciting personnel shifts at the Genoa (WI) station occurred over the winter and as we approach our spring growing season. Orey Eckes was promoted to Assistant project leader leaving a vacancy in the lead biologist position. Nick Bloomfield, currently a fish biologist at the Genoa station since 2019, competed for and received a well deserved promotion to station lead biologist. Nick came to us from the Midwest Fisheries Center in LaCrosse (WI) where he was hired by now retired project leader Pam Thiel in 2011.
He worked for the LaCrosse Fish and Wildlife Conservation Office first as a biological technician, and then converting to fish biologist. Nick has demonstrated to work well within and beyond our agency, serving as the federal coordinator for such projects as the Red River MN lake sturgeon restoration efforts involving the Minnesota Department of Natural Resources, the White Earth and Red Lake tribes of Minnesota and the Rainy River First Nation Tribe of Ontario Canada. He has managed our pond program well these past 3 years, seeing an increase in the amount of walleye production going to both host fish for Endangered Freshwater Mussel Recovery and tribal and state conservation partners. His new responsibilities will include managing our Pathways internship enrollees and Youth Conservation Corps programs and being responsible for all pond production and management stockings, including distribution records and fish population management and growth records. Congratulations and welcome to the Jungle Nick!
By: Doug Aloisi

Nick collecting fish out of a pond. Photo: Erica Rasmussen/USFWS.

Rainbow Trout eggs arrived at the hatchery on January 19th. Our friends at Ennis National Fish Hatchery, a Rainbow Trout brood facility for the Service, shipped us over 100,000 eggs overnight. After confirming the count and a quick disinfection, the eggs were placed in flow-through egg jars to finish their development. On January 26th, we noticed a few fry that had hatched in the jars, meaning it was about go-time! The eggs were placed on screens in raceways and hatching began almost immediately. By January 28th, most of the eggs had hatched. The new fry will feed off their yolk sac for the next few weeks. Next, we will watch for the telltale sign of hungry fry swimming up in the water column looking for food, our cue to start feeding. The trout will live at Genoa until next Spring, when they will hopefully be approaching 12 inches and ready to put a bend in some lucky angler’s rod. These trout will be stocked at Fort McCoy, several tribal lakes, and several fishing ponds including ours used for fishing events. Now the work begins to fatten these guys up! By: Nick Bloomfield

Rainbow Trout eggs in jars

A raceway with wire mesh screens holding eggs and fry in the water. Photo credit: Beth Glidewell/USFWS.