Grass Carp Reproduction in Small Tributaries of Harry S. Truman Reservoir, Missouri: Implications for Establishment in Novel Habitats

Abstract

Substantial work has been conducted to estimate the river length required for recruitment of invasive Grass Carp Ctenopharyngodon idella and bigheaded carps (Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix); however, the distance upstream and size of stream required for spawning remain unclear. Adult Grass Carp are regularly captured in Harry S. Truman Reservoir, Missouri, although there have been only unconfirmed sightings of Silver Carp. Fertile diploid Grass Carp are used legally for vegetation control in Missouri; however, it is uncertain whether Grass Carp in Harry S. Truman Reservoir are the result of natural reproduction or escapees. We used ichthyoplankton tows and environmental DNA (eDNA) to investigate which carp species were present in the reservoir basin and to determine whether these carps were spawning in reservoir tributaries. Grass Carp eggs were collected in four of five tributaries during June 2014. We did not detect eggs, larvae, or eDNA of Bighead Carp or Silver Carp. The occurrence of Grass Carp eggs generally coincided with rapid increases in discharge and turbidity. These tributaries may be the smallest rivers worldwide in which spawning of Grass Carp has been documented. We infer from the developmental stages captured and the distance from the reservoir that sufficient river length exists for egg survival. These results have broad implications concerning the establishment of Grass Carp in other novel habitats, including other reservoirs and lake basins, smaller rivers, and the Laurentian Great Lakes ecosystem.

Movement ecology of diploid and triploid grass carp in a large reservoir and upstream tributaries

“…While understanding of grass carp development and transport models indicates that grass carp might successfully reproduce and establish in reservoirs with tributaries of adequate length and hydraulic characteristics, it has rarely been documented. In North America grass carp reproduction is documented only in a few tributaries to lentic systems including Lake Erie, Truman Reservoir, Missouri, and Lake Texoma at the Oklahoma-Texas border [17][18][19][20]. We note that studies that would potentially document spawning of grass carp in reservoirs are rare, and established grass carp populations in reservoir basins may in fact be common, especially because grass carp captures are easily assumed to be escapees from pond stockings for vegetation control [21].…”

“…Many fish that later escaped from ponds in the watershed would also have been fertile. The Missouri Department of Conservation, which manages the Truman Reservoir fishery, does not stock grass carp into the reservoir [20]. With the discovery of successful spawning through the collection of fertilized eggs on four Truman Reservoir tributaries [20], it became evident that natural recruitment has likely increased the population in the system.…”

Winter Habitat Selection and Efficacy of Telemetry to Aid Grass Carp Removal Efforts in a Large Reservoir

“…Currently, there are no management efforts to control Grass Carp in Truman Reservoir GRASS CARP WINTER HABITAT SELECTION AND CONTROL or Lake of the Ozarks downstream, and Grass Carp are frequently caught by anglers and bow fishermen. Fertilized eggs have been collected on the Osage and South Grand rivers upstream of the reservoir (Hayer et al 2020(Hayer et al , 2021 [this special section]), suggesting that natural reproduction is occurring. An existing Grass Carp population and a variety of shallow and deepwater habitats make Truman Reservoir a suitable site in which to study Grass Carp habitat use and harvest potential within a large lentic system.…”

“…Fertilized eggs have been collected on the Osage and South Grand rivers upstream of the reservoir (Hayer et al. 2020, 2021 [this special section]), suggesting that natural reproduction is occurring. An existing Grass Carp population and a variety of shallow and deepwater habitats make Truman Reservoir a suitable site in which to study Grass Carp habitat use and harvest potential within a large lentic system.…”

Spatial suitability evaluation of spawning reach revealing the location preference for fish producing drifting eggs

“…In the direction of the river, the survey team speculated that longitudinal length of spawning ground ranges from 20 river kilometers to 70 river kilometers (Survey Team of Spawning Grounds of Domestic Fishes in Changjiang River, 1982). Additionally, Hayer et al (2021) located grass carp spawning grounds, which ranged from 47 to 107 river kilometers. These studies have provided good technical support for the protection of fish species that produce drifting eggs.…”