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US Fish & Wildlife Service FieldNotes

A pistol to propagate: A three year journey ends in success!

Region 3, June 3, 2013
Flathead catfish transferred from FWS biologists to Iowa DNR for over winter holding.
Flathead catfish transferred from FWS biologists to Iowa DNR for over winter holding. - Photo Credit: n/a
Jorge Buening, Genoa NFH biologist places a mussel cage holding flathead catfish bearing pistolgrip larvae.
Jorge Buening, Genoa NFH biologist places a mussel cage holding flathead catfish bearing pistolgrip larvae. - Photo Credit: n/a

During May the first ever batch of pistolgrip mussels was inoculated on host fish at Genoa National Fish Hatchery. While it is always exciting to propagate a new species, this one was particularly special because it was three years in the making.

Most mussels propagated by Genoa National Fish Hatchery spawn in the fall, brood their larvae over winter and can be collected gravid for over six months out of the year. The pistolgrip is different in that it spawns in the spring and releases larvae weeks later. This happens in April or May, a time when the local streams are swollen from rains and snow melt.

Two years ago our attempts to collect gravid pistolgrip were successful, only to see the effort wasted as we were unable to collect their host fish, the flathead catfish, because of spring flooding. Last year cooperation from multiple state partners led to the collection of flathead catfish in the fall, and their holding over winter at the Iowa Department of Natural Resources' Fairport Hatchery. An unseasonably warm spring last year opened and closed the brooding window before our divers had a chance to look at our favorite pistolgrip collection locations and another season was lost.

This year everything came together beautifully. A suitable number of flathead catfish were collected by the Nebraska Department of Natural Resources and survived over winter at the Fairport Hatchery.  Multiple female pistolgrip were collected brooding viable mussel larvae. 120 flathead catfish were inoculated with pistolgrip larvae. These fish have been placed in mussel culture cages at three separate locations within the Upper Mississippi River Watershed to assure that culture will be successful. The cages will be examined in the fall and any resulting sub-adult mussels will be marked with a tag for identification and stocked in either the Iowa or Mississippi Rivers. Our laboratory estimates indicate that each fish will produce over 1,300 juvenile pistolgrip resulting in a total production of 149,200 mussels for this effort.

Many thanks to all of our partners who helped us get a grip on the pistolgrip this season.

Contact Info: Nathan Eckert, 608-689-2605 ex 115, Nathan_Eckert@fws.gov