Mussel Biologists Dazzled by 50,000 Juvenile Winged Mapleleaf Mussels



Displaying winged mapleleaf  Credit: Megan Bradley, USFWS

Each fall, hatchery biologists working with U.S. Park Service staff, Minnesota DNR mussel biologists and staff from other U.S. Fish and Wildlife Service offices visit the St. Croix River as many as 15 times looking for the federally endangered Winged Mapleleaf that thrive in the clean, clear water. Females holding mussel larvae are brought back to Genoa National Fish Hatchery (NFH), the larvae (glochidia) are allowed to attach to channel  catfish and then the female mussels are returned to the St. Croix River.  In the wild the larval mussels remain attached to the catfish until late spring when the water begins to warm. Hatchery staff has worked hard to replicate this experience for the catfish and their mussel  riders in the lab but it has proven to be challenging. In late fall 2016 Genoa’s mussel biologists moved 38 channel catfish, just a small part of the 410 infested with winged mapleleaf more than a month before into an aquarium system where they are warmed up to replicate spring’s warming water temperatures.  By the week of Thanksgiving the first juvenile winged mapleleaf of 2016 were collected. The first vision of newly transformed juvenile mussels is more akin to stars in a very dark sky. Only by putting the dish on the  microscope do the tiny moving spots take on the shell and foot characteristic of their adult counterparts. Juvenile mussels are counted on the microscope by estimating the number in each square of the dish. Some days this takes ten minutes, other days it can take an hour. Every other day, juveniles are collected, counted and moved from their dish into the system where they’ll eat and grow. Winged mapleleaf are a challenging species to culture and are especially delicate when young, thus the reason for our excitement!

Viewing Juvenile winged mapleleaf under a microscope

Credit: Megan Bradley, USFWS

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