Common carp management using biocontrol and toxins

Project manager: Przemek Bajer

Funded by: Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources

Description: This project will test whether common carp can be baited and killed using corn pellets with antimycin-a, a natural fish toxin, without harming other species. Although other biocontrol strategies – such as using bluegills to consume carp eggs – are successful on some lakes, they are unsuccessful on lakes which are prone to winterkilling. Carp have a unique diet (plant seeds, such as corn, which native fish are not attracted to) and can be trained to aggregate in baited areas. Researchers will first determine the concentration of antimycin-a needed and the species-specificity of the approach.  They will then conduct trials to test this “bait and switch” concept with carp of different sizes in experimental ponds.  

This project will also test through whole-lake experiments whether bluegills can be used as a biocontrol agent for common carp. Researchers will conduct experiments on both moderately productive and very productive lakes, measuring carp and bluegill density over two seasons. Survival of carp eggs, larvae, and fry will be monitored at appropriate intervals throughout the study. Water quality and zooplankton abundance (food for larval carp) will be also measured as it might provide additional information about the survival of carp larvae and fry. Researchers will also analyze previously collected DNR data to evaluate whether aerating shallow lakes in the winter affects carp recruitment.

Project start date: 2015

Estimated project end date: 2017, Phase 2 to continue through 2019

Updates:

Progress:

We tested two new methods to control common carp. First, we tested biocontrol, which is the ability of bluegill sunfish (native) to control carp reproduction by consuming their eggs and larvae. This was tested in 6 small lakes. All lakes were stocked with adult carp and every other lake was stocked with bluegills. Carp offspring survival was assessed through electrofishing and mark-recapture. At the end of the season, lakes with bluegills had 11 times fewer carp offspring than those without bluegills. This shows that biocontrol by bluegill is an important element of common carp management strategies. Bluegill populations can be strengthened in many shallow lakes by winter aeration to prevent winter fish kills.

Second, we tested if toxic bait could be developed to target carp without impacting native fish. This is important in lakes where biocontrol is unlikely. We incorporated an EPA-approved toxin antimycin-A (ANT-A) into corn pellets, which the carp consume with high specificity and performed 4 experiments: 1) using gavage trials we showed that the bait was toxic at 8 mg/kg; 2) using leaching trials we showed that <1% of ANT-A leached out of the bait and did not cause mortality among native fish; 3) using lab tanks where carp were stocked with three native fish we showed that 46% of carp and 76% of fathead minnows perished after one application of pellets, but perch and bluegill were not impacted; 4) using ponds with carp, bluegills and perch we showed that 37% adult carp perished after 6 days of pellet application, while no perch and bluegill did. Our results suggest that corn-based toxic pellets could be developed to selectively target carp but more work is needed to minimize impacts on native minnows. This is being addressed by ongoing work.