Host fishes as ecosystems- managing disease while protecting developing mussels.

Propagating mussels is difficult for lots of reasons, but their dependence on a live host fish always creates a challenge. Fish survival at the hatchery is usually strong, but the more you handle them, the more prone they are to disease since you damage the protective mucous coat or even dislodge scales and infesting fish with freshwater mussel glochidia involves a lot of handling. Propagation becomes even more arduous when the glochidia transform over months, rather than weeks since you have to keep your fish healthy over long, cold months when they don’t eat much and they’d rather be buried in the mud in a deep river hole. Successfully producing juvenile Winged Mapleleaf, a federally endangered mussel, depends on this over-wintering, as does the Washboard, North America’s largest native freshwater mussel.
Less successful seasons see the loss of these host fish due to disease, and therefore the loss of Winged Mapleleaf larvae, but treatments are required to manage illness, while not harming the developing glochidia. One of our graduate pathways interns has taken this topic on as her graduate thesis work. She is treating Washboard-infested Channel Catfish weekly with typical fish disease treatments to determine whether they decrease the number of quality of juveniles dropping off the fish in the spring. Many treatments have been tested in bass infested with Plain Pocketbook to confirm that they don’t impact the new juveniles, but none have been tested for multiple uses, or over multiple months. Being able to manage disease in Winged Mapleleaf-infested Channel Catfish will make a difference in the success of the recovery program for this species and others across the country.
By: Megan Bradley