Distribution, abundance and overwinter survival of young-of-the-year common carp in a Midwestern watershed.

Abstract

The common carp (Cyprinus carpio) is one of the most widespread and damaging invasive fishes in North America, yet little is known about its early life history. This paper reports the results of two studies which tested the hypothesis that shallow lakes prone to winter hypoxia (i.e. unstable lakes) serve as nurseries for common carp in interconnected lake systems while lakes that do not experience winterkill (i.e. stable lakes) do not function as nurseries. Six lakes in an interconnected lake system in southcentral Minnesota (four stable and two unstable) were sampled using trap-nets in June- August of 2009, 2010 and 2011 and in all three years age-0 carp were captured only in the two unstable lakes. These surveys also revealed that the fish communities in stable lakes were dominated by bluegill sunfish and largemouth bass, species which did not occur naturally in the unstable lakes. Mark-recapture and ageing studies conducted in 2010 in the two carp nurseries indicated that there were ~13,000 age-0 carp in Casey Lake and ~35,000 age-0 carp in Markham Lake. Additional mark-recapture efforts the following summer indicated that ~33% of those fish survived their first winter in Casey Lake while ~4% survived in Markham Lake. Independent trap-net and electro-fishing surveys in the nursery lakes in 2010 revealed that their fish communities were dominated by shorter length classes of hypoxia-tolerant species. Implications of these results for management of nuisance carp populations in interconnected lake systems in North America are discussed.