Genoa NFH Assistant Manager, Roger Gordon and Mussel Biologist Tony Brady squeeze by each other in the Clam Palace, as Wisconsin DNR Biologist Dave Heath gets a bucket of fish for inoculation. - USFWS photo

Gravid endangered Higgins' eye pearlymussels collected from the Mississippi River for propagation efforts at Genoa NFH. - USFWS photo

As the weather slowly warms and dandelions explode all around the hatchery, Genoa National Fish Hatchery staff and volunteers from US Geological Survey, LaCrosse Fisheries Resource Office, Twin Cities Field Office, and the Wisconsin, Minnesota, and Iowa Department of Natural Resources are busy with Endangered Higgins' eye pearlymussel propagation activities at the Clam Palace.

Genoa NFH has been involved with Higgins' eye recovery since 1999 when critical habitat areas for the Higgins' eye in the Mississippi River were impacted by the invasive zebra mussel. The zebra mussels reproduce in excessive numbers and then the young zebra mussels attach to hard surfaces, such as native mussel shells, eventually forming a thick layer encrusting the outsides of the native mussels. The encrusting layer of zebra mussels robs all the food from the native mussels and prevents the natives from completing their complicated life cycle.

Native mussel such as the Higgins' eye requires fish to carry their larval form called glochidia. Higgins' eye use a "fishing lure" to attract fish close enough to release glochidia into the fish's mouth where the glochidia are passed to the gills and there attach to the fish for several weeks. While on the fish's gills, the glochidia receive nutrients needed to complete their metamorphoses into free living juvenile mussels that drop to the rivers bottom.  

Volunteers assist the Genoa NFH staff  with inoculating host fish with glochidia, thus helping Higgins eye complete their life cycle. In small buckets, volunteers introduce largemouth bass and walleye to Higgins' eye glochidia, and after several minutes of exposure to the glochidia, the volunteers bring a fish to Genoa staff to be checked for the level of infestation.  A target rate of 400 glochidia per fish is the goal of this infestation process with over 3.2 million potential juveniles to be produced this summer.

Fifty-eight adult Higgins eye pearlymussels were collected to infest 7,950 host fish.  These mussels are collected by SCUBA divers from Genoa NFH and Minnesota DNR, who scour the bottom of the St. Croix and the Mississippi rivers for the gravid females. Two to three weeks after the infestation process, fish will be either be released into Mississippi River tributaries in Wisconsin and Iowa, while the remaining fish will be placed in cages in Lake Pepin, MN and Ice Harbor in Dubuque, IA. Higgins eye pearlymussels propagated in cages are protected from predators such as carp and suckers, and provides an opportunity to quantify the success of this program. Higgins eye pearlymussel propagation efforts have produced over 11,000 juveniles in cages since 2000 with over 7,000 two or three year old sub-adult mussels being placed back into the upper portions of the Mississippi River.