Although the common carp is globally distributed, it only reaches extreme densities in certain regions. We hypothesized that this phenomenon might be linked to recruitment bottlenecks which carp overcome where environmental conditions create unstable peripheral areas that it can access for spawning and nursery habitat. To test this hypothesis, the abundance, movement and reproductive success of carp was determined in two systems of inter-connected lakes in the North American Midwest whose shallow basins frequently experience winter-hypoxia ('winterkill'). Radio-tracking demonstrated that while adult carp overwinter in deep lakes that do not winterkill, they aggressively move into winterkill-prone shallow regions in the spring to spawn. The significance of this behavior was demonstrated by ageing analyses which found that carp recruit only in interconnected shallow lakes and then only in years following severe winter hypoxia. Presumably this strategy allows carp to exploit nursery habitat that is relatively free of predators. It likely evolved in response to seasonally variable conditions in the carp's native habitat in the Ponto-Caspian region. This life history may also explain the carp's abundance in other unstable regions such as southern Australia and could potentially be exploited to control this damaging invasive.
Bibliographical noteFunding Information:
Acknowledgments We thank Daryl Ellison, Paul Diedrich, and Lee Sundmark [Minnesota Department of Natural Resources (MN DNR)] for providing historical records of winter hypoxia and fish winterkills in the study lakes. Michael McInerny (MN DNR) and Brett Miller [University of Minnesota (UofMN)] verified age estimates. Mario Travaline (UofMN) conducted carp female egg-counts. Jack Wingate, Tim Cross, Michael McInerny, Nicole Hensel-Welch, Eric Altena (MN DNR), Haude Levesque (UofMN), Tiffany Babich, Greg Aamodt (Carver County Water Management), Dave and Ann Florenzano, John Bushey, and Mike Domke (Lake Riley Association) and other volunteers helped with data collection. Matt Hennen helped with carp telemetry. Ken Seemann conducted seining operations. Paul Brown (Department of Primary Industries, Victoria, Australia) helped with developing procedures to age common carp in our laboratory. Howard Peterson provided encouragement. This research was supported by grants from the Minnesota Environmental and Natural Resources Trust Fund, Riley Purgatory Bluff Creek Watershed District, MN DNR—Ecological Services, Invasive Animals Cooperative Research Centre, and a generous contribution from Bill Oemichen whose early encouragement was greatly appreciated. The Minnesota DNR Fisheries Division also provided in-kind support. We thank an anonymous reviewer for helpful comments on the manuscript.
- Life history
- Predatory release
- Propagule pressure