Ammonia as a tool for removal of invasive crayfish
Channel: Conservation and Adaptation Resources Toolbox
Date: 2023-08-01

The opportunistic feeding habits of nonnative crayfish have negatively affected native aquatic species in the southwestern United States, and their ability to travel between isolated aquatic systems make them difficult to control once they become established. Efforts to manually remove crayfish from invaded habitats have been met with limited success and few chemical tools are available. Ammonia has shown promise as a removal tool for introduced fish, is less toxic than some other chemical control tools, and utilizes the natural nitrogen cycle to return an ecosystem to baseline conditions. I used laboratory experiments to develop and test lethal concentrations of ammonia for Northern Crayfish (Faxonius virilis) and Red Swamp Crayfish (Procambarus clarkii). Using a formulation of ammonium sulfate, sodium carbonate, and sodium sulfite, I achieved 100% mortality of F. virilis and 90% mortality of P. clarkii in controlled tanks. A field trial with P. clarkii also killed most of the crayfish exposed to the ammonia treatment. Future research should focus on further exploring species differences, the effectiveness of ammonia treatments under diverse field scenarios, and returning treated areas to safe conditions for native species.
Presented by Susan Wood, Fish Biologist, Grand Canyon National Park
July 27th, 2023