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Invasive Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix have infested and caused largescale ecological and economic damage to the Illinois, Mississippi, and Ohio rivers. We compiled demographic data from 42,995 fish from 23 pools in the Illinois, Mississippi, and Ohio rivers, which universities and management agencies previously collected as part of management, monitoring, and research activities. We used this data set to test whether demographic rates (length–weight relations including body condition, mortality, growth curves, and female maturity curves) varied among subpopulations across a gradient of invasion status. We found that length–weight relations and growth curves varied among subpopulations, whereas maturity curves did not. Our findings demonstrated spatial variability in demographic rates for Bighead and Silver carp across a broad geographic area in relation to invasion status and river conditions. Herein, we provide general subpopulation management options and present different hypotheses to explain the observed spatial variability in demographic rates.

The first winter of life can play an important role in the success of age‐0 fishes. First‐winter survival is often size dependent, with larger fish exhibiting higher survival than small fish. Cohorts of age‐0 saugeye female Walleye Sander vitreus × male Sauger S. canadensis stocked into Ohio reservoirs exhibit overwinter shifts toward larger body sizes; however, it is unclear whether growth, size‐dependent mortality, or size‐dependent emigration underlie this phenomenon. Saugeye may experience low prey availability during the overwinter period, making them especially vulnerable to starvation. Furthermore, survivors emerging from winter in poor energetic condition may experience reduced spring foraging success and growth. We used a combination of overwinter PIT tag studies in the field and overwinter outdoor pool experiments to understand these direct and indirect effects of winter on survival and size distributions of cohorts of saugeye. Using PIT tags to allow us to track growth of individuals in reservoirs, we found that saugeye of all sizes increased in length over winter, there was no evidence of size‐dependent overwinter mortality, and rates of emigration out of the reservoir were greater for large saugeye than small saugeye. Thus, only growth rate, and not mortality or emigration biased toward small fish, can explain the observed overwinter shift in size distributions. In pool experiments, we found no direct effects of winter on survival, even in the complete absence of food, and no negative consequences of starvation over the winter on the ability of saugeye to resume feeding in the spring. Our results suggest that shifts in size distributions of first‐year cohorts over winter are driven by growth rather than mortality. Neither direct effects of first winter on survival nor indirect effects mediated through effects of starvation on future foraging ability are important in recruitment success of saugeye in Ohio reservoirs. Received March 18, 2014; accepted June 30, 2014

Invasive species management can benefit from predictive models that incorporate spatially explicit demographics and dispersal to guide resource allocation decisions. We used invasive bigheaded carps (Hypophthalmichthys spp.) in the Illinois River, USA as a case study to create a spatially explicit model to evaluate the allocation of future management efforts. Specifically, we compared additional harvest (e.g. near the invasion front vs. source populations) and enhanced movement deterrents to meet the management goal of reducing abundance at the invasion front. We found additional harvest in lower river pools (i.e. targeting source populations) more effectively limited population sizes upriver at the invasion front compared to allocating the same harvest levels near the invasion front. Likewise, decreasing passage (i.e. lock and dam structures) at the farthest, feasible downriver location limited invasion front population size more than placing movement deterrents farther upriver. Synthesis and applications. Our work highlights the benefits of adopting a multipronged approach for invasive species management, combining suppression of source populations with disrupting movement between source and sink populations thereby producing compounding benefits for control. Our results also demonstrate the importance of considering metapopulation dynamics for invasive species control programs when achieving long‐term management goals.