Friends of the Upper Mississippi

Higgins Eye Pearlymussel in sand. Photo: USFWS.

Megan Bradley, a mussel conservation biologist at the Genoa National Fish Hatchery in Genoa, Wisconsin, recently received news that she will receive the coveted 2022 FWS Midwest Region Recovery Champion Award for her work with federally endangered freshwater mussels in the Upper Mississippi River. Megan worked with other agencies, tribes and national and international partners to improve the status of several species of imperiled mussels through her efforts to map suitable habitat, create new populations, monitor released mussels and planning and implementing programs to raise and release endangered species like the Higgins Eye Pearlymussel, the Winged Mapleleaf mussel and the Spectaclecase mussel.
Megan has also been instrumental in establishing the cost of replacing mussels affected by environmental contaminants through the NRDA process, enhancing the ability to recover damages and restore these species. She has also been responsible for helping to produce multiple year classes of a number of species of mussels for release into spill impacted areas, some of which included the Endangered Higgins Eye Pearlymussel. Congratulations Megan! We are proud to serve alongside of you!
By: Doug Aloisi

Megan in dive gear holding a mussel in one hand. Photo: USFWS.

BY BETH GLIDEWELL, GENOA NATIONAL FISH HATCHERY

The Hine’s Emerald Dragonfly (HED) eggs that were housed at Genoa National Fish Hatchery over the winter began hatching in late March and by late May, 445 eggs had successfully hatched. These eggs arrived on station last November and were kept at cool, stable temperatures all winter. Eggs are kept by female line in sample cups of clean water and are checked frequently for fungal growth or other problems. Water is exchanged every other week to maintain good dissolved oxygen levels.

As temperatures began to warm outside this spring, we warmed the egg chamber slowly over several weeks and then above the critical hatching temperature of 42-43 °F. Cups are checked daily during the warming period for newly hatched larvae. As larvae hatch, they are pi petted out of the egg cup into their own specimen cup filled with about 20 milliliters of clean water of the same temperature water.

These new juvenile cups are allowed to slowly warm to room temperature in the mussel building, where they are fed zooplankton two to three times per week. Pond water that is pumped into the mussel building for fish housing and mussel culture is also filtered through a series of mesh screens, and zooplankton that are between 55 to 300 microns are retained, concentrated, and ‘fed’ or pipetted into each juvenile cup. This mixture of rotifers, cladocerans, copepods and other naturalized pond zooplankton make great Hine’s Emerald larvae food, and also feeds young of the year fish cultured in the various ponds at the hatchery.

The juvenile dragonflies will be housed in these cups until early to mid-June when they’ve (hopefully) grown large enough to be moved to screened cages or ‘s-cages’ that can be kept in larger, flow-through tanks in the dragonfly trailer all summer. Stay tuned for pictures and updates from this next stage of HED culture!

Above: HED eggs stored at stable temperatures over winter. The eggs are housed at about 39 degrees Farenheit from November to March. Credit: Beth Glidewell/USFWS

KIDS SPRING FISHING DAY
SATURDAY, MAY 14, 2022
8:30 AM—12:00 PM
Genoa National Fish Hatchery
Join staff from the 3 La Crosse area U.S. Fish and Wildlife Service Fisheries Offices and our Friends Group, the Friends of the Upper Mississippi for a day of fishing fun!
This popular annual event is for children 5-12 years old who are accompanied by a parent or guardian. The event begins with hands-on learning sessions about fishing techniques and conservation, then children are allowed to fish in a stocked hatchery pond.
Bait will be supplied, with no outside bait allowed due to biosecurity concerns.
FOR MORE INFORMATION
Email: Erica_Rasmussen@fws.gov
Or call: 608-689-2605

BY MEGAN BRADLEY AND BETH GLIDEWELL, GENOA NFH

Have you ever wondered what it takes to get two biologists to the bottom of the Mississippi River looking for our native freshwater mussels? Each year our mussel biologists complete training, take their gear for servicing and then reassemble their kits to make sure they can safely dive for the season. Gear servicing involves ensuring that tanks that hold their air are safe and sealed, taking the regulators they breathe with to be cleaned, as the filters inside of them collect fine silt from the water and their occasional contact with the river bottom, and confirming that the vests they wear to be able to return to the surface are able to hold air. Most of a day is spent in the pool, proving that we can swim nearly a mile and refreshing a few basic SCUBA skills in a low-stress environment.   Thanks to all of the preparations divers will be ready to begin collecting native mussel broodstock as soon as air and water temperatures warm up.

Above: Divers share air before ascending to the surface. This is an important skill to practice for divers so that in case of an emergency the methods are ingrained. Credit: USFWS.

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