BROOKINGS — In South Dakota, invasive carp (formerly known as Asian carp) have made their way into the James River, the Big Sioux River and the Missouri River below Gavins Point Dam. Physical barriers are keeping "America's most unwanted fish" from swimming farther up the Missouri River — and South Dakota officials and researchers are eager to keep it that way.
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BROOKINGS — In South Dakota, invasive carp (formerly known as Asian carp) have made their way into the James River, the Big Sioux River and the Missouri River below Gavins Point Dam. Physical barriers are keeping "America's most unwanted fish" from swimming farther up the Missouri River — and South Dakota officials and researchers are eager to keep it that way. While flooding poses a potential pathway for carp to circumvent these physical barriers, human-mediated introductions — such as the release of juvenile carp via live bait — are a similar pathway of concern. "Juvenile invasive fish may be inadvertently released by anglers, resulting in potential negative ecological, economic and social impacts," said Hannah Mulligan, a graduate research assistant in South Dakota State University's Department of Natural Resource Management. New research from Mulligan and her colleagues was the first of its kind to explore the live bait trade in the Missouri River basin. Through environmental DNA monitoring, Mulligan found that bigheaded carp — a catch-all term for silver and bighead carp — DNA had been present in commercial bait shops throughout the region. "The live bait trade represents a potential human-mediated, weak-link pathway for invasions," Mulligan said. Mulligan and her colleagues conducted this study, which was published in the academic journal Biological Conservation under the title "Opportunities for regional collaboration and prevention: assessing the risk of the live bait trade as a pathway of invasive species," during the summer and fall of 2022, when they visited 112 bait retailers in North Dakota, South Dakota, Iowa, Nebraska and Kansas. The team collected water samples from each retailer and tested them for bigheaded carp DNA. Ten water samples from 10 different bait retailers tested positive for bigheaded carp DNA in North Dakota (one positive), South Dakota (four positives), Iowa (four positives) and Kansas (one positive) during the summer collection period. The team then collected an additional 60 water samples in the fall from 30 bait retailers in South Dakota, 18 of which were resampled from the initial round of testing. Five water samples from four bait retailers tested positive for bigheaded carp DNA. "One bait retailer tested positive for bigheaded carp during both sampling periods" Mulligan said. "Three bait retailers that had DNA during the initial sampling were negative when resampled. One bait retailer that did not have DNA during the initial sampling period had DNA during the second sampling."