AUTHORS: Kellie Hanser, U.S. Fish and Wildlife Service; Jessica Howell, jessica_howell@fws.gov; Jason Goeckler, jason_goeckler@fws.gov
ABSTRACT: Silver Carp (Hypophthalmichthys molitrix) relative abundance and demographic information is essential to guide management and control measures. Interconnection across river basins has allowed Silver Carp to establish a reproducing population along the entirety of the free-flowing portion of the Missouri River and its tributaries. Population information is being collected with an electrified dozer trawl to establish baseline invasive carp data in tributary confluences to monitor populations and guide management efforts as they begin to increase. Because Silver Carp are located throughout the Missouri River, tributaries are sampled along a large spatial gradient (river miles 170 – 800) to help track and delineate populations trends across the basin. From 2020 – 2023, a total of 611 transects have been completed collecting over 29,000 individuals from 50 different species. However, most fish sampled are invasive carp with the total number of individuals exceeding 15,000. Data shows that Silver Carp across tributaries are demographically similar, with large older individuals in the higher latitude tributaries. Age data indicates the 2019-year class is still currently dominant across the basin. Annually, the relative abundance, size structure, body conditions, sex ratio, age structure, recruitment, growth, and mortality are analyzed and provided through the Missouri River Basin Invasive Carp Partnership in a collaborative effort to help inform the Silver Carp status for the basin.
