Density-Dependent Overwinter Growth and Survival of Juvenile Bigheaded Carp

For many fish species recruitment bottlenecks can occur when young individuals experience high rates of overwinter mortality.  Invasive bigheaded carp (Bighead and Silver Carp) have high recruitment potential, possibly leading to high densities of juveniles in Midwestern rivers. High densities may have an effect on resource availability, energy storage and can ultimately contribute to poor overwinter survival.  However, overwinter growth, mortality, and the potential effects of density-dependence have yet to be quantified for juvenile bigheaded carp.  To evaluate this, age-0 Silver Carp and age-1 Bighead Carp were stocked into 0.04 hectare ponds in early December 2015.  Silver Carp were stocked at low densities (20 individuals) into 5 ponds.  Bighead Carp were stocked at low (25 individuals), medium, (125 individuals), and high (225 individuals) densities, with 5 replicate ponds per treatment.  A subset of bigheaded carp were individually marked to track individual growth rates.  Ponds were drained when water temperatures reached > 10 ºC for 1 week and growth, survival, and energy density were quantified and compared across density treatments.