Improving Survival of Juvenile Winged Mapleleaf Mussels (Quadrula fragosa) Through Identification of Host Fish Overwintering Areas

Science Center Objects

The St. Croix National Scenic Riverway (SACN) is one of the last refuges for rapidly declining populations of native unionid mussels in the United States and supports the only known self-sustaining population of the federally endangered Winged Mapleleaf mussel (Quadrula fragosa) in the upper Mississippi River basin. The Channel Catfish (Ictalurus punctatus) is the only known host for Winged Mapleleaf in the St. Croix River. Although Channel Catfish are common in the St. Croix Riverway, little is known about the frequency of natural Winged Mapleleaf infestations on their host fish. The main objectives of this study were to characterize the patterns of Channel Catfish during the mussel’s glochidial release, encystment, and juvenile release periods and to assess the range of the Channel Catfish during the juvenile excystment period to aid in identifying areas for follow-up monitoring and mussel reintroduction. 

In 2016, 35 Channel Catfish were internally tagged with a Lotek transmitter, and in 2017 48 Channel Catfish were implanted with transmitters. A majority of the Channel Catfish remained in the St. Croix River (1 tagged in 2016 and 4 tagged in 2017 moved to Prescott, Wisconsin) over the 2.5- year study. We identified primarily two locations where Channel Catfish overwinter, the Folsom Island area and in Lake St. Croix, near Hudson, Wisconsin. Most of the tagged Channel Catfish moved to these overwintering areas by the end of November and stayed there until spring. Our telemetry data suggests that Channel Catfish spatially overlap with the Winged Mapleleaf mussels during the end of August through mid-September, which is the time period  of gravidity in the Winged Mapleleaf mussel. Some of the Channel Catfish returned to the mussel bed location at Folsom Island in the spring, during the period of juvenile release from their fish host, but some Channel catfish remained in Lake St. Croix. The Hudson area may be an additional focus for follow-up monitoring and our research indicates that there may be interactions between the mussels located at Folsom Island and the experimental mussels (artificially propagated) located at Hudson, Wisconsin.  

Brooding Winged Mapleleaf displaying its mantle magazine during September in the St. Croix River.

Brooding Winged Mapleleaf displaying its mantle magazine during September in the St. Croix River.

(Credit: Mark Hove, University of Minnesota. Public domain.)