"Carbon dioxide for eradicating invasive fish from anchialine pools" by Robert Peck (Pres 30: 5ISAE)
This presentation was a part of the 5th International Symposium on Anchialine Ecosystems (5ISAE), held in Kailua-Kona November 3-5, 2022.
Presentation 30: "Carbon dioxide (CO2) as a tool for eradicating invasive fish from Hawaiian anchialine pools: A case study at Pu‘uhonua O Hōnaunau National Historical Park"
Session 7: Hawai‘i - Biological Sciences
Presentation Authors: Robert Peck (1), Maya Munstermann (1), Malia Hayes (2), Carter T. Atkinson (3), Aaron Cupp (4) and Paul Banko (3)
Affiliations: (1) Hawai‘i Cooperative Studies Unit, University of Hawai‘i at Hilo, Hilo, HI, USA; (2) Pu‘uhonua o Hōnaunau National Historical Park, Hōnaunau, HI, USA; (3) U.S. Geological Survey, Pacific Island Ecosystems Research Center, Volcano NP, HI, USA; (4) U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, USA
Presentation Abstract: The incursion of invasive fish into Hawaiian anchialine pools has resulted in profound negative impacts on faunal diversity and threatens the long-term survival of several endangered invertebrate species. Removal of invasive fish from anchialine pools is a priority for land managers aiming to restore this unique brackish coastal ecosystem. This study tested the efficacy of carbon dioxide (CO2) diffused into anchialine pool water as a tool for eradicating Mozambique tilapia (Oreochromis mossambicus), guppies (Poecilia reticulata) and western mosquitofish (Gambusia affinis), invasive species common in Hawaiian anchialine pools. We also tested CO2 against several species of native invertebrates to gauge potential non-target impacts and developed qPCR and isothermal DNA amplification assays for detecting environmental DNA (eDNA) from all three fish species. Aquarium trials indicated that pH 5.3 and 5.0 would kill or greatly affect the behavior of tilapia and the poeciliids (guppies and mosquitofish), respectively. We then treated an anchialine pool at Pu‘uhonua o Hōnaunau National Historical Park on Hawai‘i Island with CO2 to attempt to eradicate tilapia. CO2 was applied to this pool on four occasions, with decreasing numbers of survivors after each treatment. Repeated visual surveys spanning ten weeks following the final treatment suggested that tilapia had been removed from the pool. An assessment of pool water using eDNA detection protocols failed to detect tilapia supporting the conclusion that tilapia had been eradicated. This presentation will discuss the lessons learned during this process, including expectations for managing invasive fish and potential uses of eDNA for surveys of anchialine pools.