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Like many invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.

Learn more about invasive species , Bighead (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix)—collectively nicknamed ‘bigheaded carp’—are known for their hardiness, high fecundity, dispersal abilities, and competitive advantage against native aquatic species in the United States. While our understanding of their ecology, life history, and population dynamics in the upper Mississippi River basin has grown substantially over the last two decades, bigheaded carp continue to overturn the limiting factors we have ascribed to their reproduction and movement (Sampson et al. 2009; Deters et al. 2013; Coulter et al. 2013). As a result, the development of effective management and control strategies in these inundated regions has been slow and arduous. In recent years, an influx of resources was allocated to the understudied subbasins of the lower Mississippi River, where bigheaded carp currently persist in relatively lower densities. This opportunity has resulted in the formation of extensive partnerships between government agencies, conservation groups, universities, commercial and recreational anglers, business owners, and landowners—all with the common goal of developing proactive strategies for managing populations and preventing further translocation of bigheaded carp. 

There are numerous native, state-listed species vulnerable to the growth of bigheaded carp populations in the Red River, including the planktivorous American Paddlefish (Polyodon spathula), Blue Sucker (Cycleptus elongates), Plains Minnow (Hybognathus placitus), American Eel (Anguilla rostrate), and Blackspot Shiner (Notropis atrocaudalis). Also facing significant risk is the recreational value of Lake Texoma and its renowned recreational Striped Bass (Morone saxatilis) fishery. Each year, the reservoir attracts approximately 965,000 visitors, generating a regional total of $159 million (U.S. Army Corps of Engineers 2012). While the Denison Dam currently serves as an effective barrier to all fish movement from the Red River upstream into Lake Texoma, the translocation of juvenile bigheaded carp (closely resembling native Clupeids) via angler bait buckets is a viable concern. The threat of Silver and Bighead Carp introduction to Lake Texoma is compounded by the potential for translocated individuals to find suitable spawning habitat on the Washita and Red River arms of the lake. Grass Carp (Ctenopharyngodon idella), which share similar spawning cues and conditions with bigheaded carp, have demonstrated successful recruitment here already (Hargrave and Gido 2004; Sheltonand Snow 2017). 

To date, there has been no evidence to suggest that bigheaded carp have recruited within our Red River study area; however, Patton and Tackett (2012) speculated that the river conditions appeared to be conducive to their spawning, with the extreme hydrologic fluctuations from the Denison Dam potentially contributing to a flood pulse spawning cue. Since the inception of the Arkansas-Red-White partnership for invasive carp in 2020, hundreds of fecund bigheaded carp have been collected from the Red River drainage in Texas and Oklahoma. As the partnership continues evaluating the status of these species to inform future management strategies, the Oklahoma Fish and Wildlife Conservation Office (OKFWCO) will assist efforts by monitoring the status of bigheaded carp recruitment in the Red River and its tributaries below the Denison Dam in Oklahoma and Texas (Figure 1).

The OKFWCO’s Monitoring for bigheaded carp recruitment in the form of eggs and larvae was conducted using larval fish tows and light trapping. Using traditional methods, samples collected from these efforts would need to be physically sorted and visually inspected to identify potential bigheaded carp. This process is incredibly time consuming, and species ID based on physical characteristics of these samples is not possible in many cases (Camacho et al. 2019). Recently, Fritts et al. (2019) demonstrated that aliquots of the ethanol used to preserve these samples could be screened using quantitative PCR (qPCR) to identify collections which contained invasive carp eggs and or larvae. Although this method was not 100% accurate, this information could then be used to select those tow and trap samples which should be further screened for the presence of larval fish and eggs. The objective of this study was to use qPCR screening protocols developed by Fritts et al. (2019) to screen ethanol preserved samples collected by the OKFWCO for the presence of Silver and Bighead carp DNA. Any samples that do test positive for bigheaded carp DNA can then be further screened using visual ID and additional genetic methods (e.g., species ID sequencing).