The optimal stocking strategy for Yaqui Catfish

ObjectiveThe Yaqui Catfish Ictalurus pricei, a species that is endemic to the southwestern United States and west-central Chihuahua and Sonora, Mexico, is extinct in the United States and extremely endangered in Mexico due to habitat loss and hybridization with nonnative Channel Catfish I. punctatus. To re-establish populations in the United States, a binational program consisting of broodstock collection, fish propagation, stocking, and poststocking monitoring is necessary. This programmatic approach is encapsulated within a Conservation Propagation and Stocking Program (CPSP), which documents important recovery actions, such as genetic management, fish culture, stocking, and poststocking assessments. The focus of our work is to identify the optimal stocking strategy for Yaqui Catfish, thereby informing the framework of a CPSP for the species' recovery.MethodsOur strategy involved simulating population growth using an age-structured simulation model with varying stocking contribution rates, stocking densities, and stocking frequencies and incorporating these biological data with economic information within a utility function to quantify stocking costs.ResultThe optimal strategy requires releasing Yaqui Catfish at a density of 200 fish/ha every 5 years. This strategy excludes natural recruitment because historically, stocked Yaqui Catfish inhabited waters that were either too small or devoid of habitat to induce natural spawning. However, if larger waters or waters having appropriate habitats (e.g., interstitial spaces) are also stocked, it should increase natural recruitment, thereby (1) enabling populations to become self-sustaining and (2) drastically reducing the reliance on hatcheries for stocking and salvage of declining populations.ConclusionOur results provide important stocking recommendations within a CPSP, emphasizing the need to build a broodstock before genetically pure Yaqui Catfish disappear. The successful implementation of the optimal stocking strategy requires multiple locations for stocking fish and is contingent on strengthening binational partnerships. This approach fills an important void in Yaqui Catfish reestablishment, helping to prime the successful recovery of this species. The Yaqui Catfish, once native to regions of the United States and Mexico, faces near extinction due to habitat degradation and nonnative hybridization. A binational Conservation Propagation and Stocking Program offers a promising solution, suggesting for the release of 200 fish per hectare every 5 years in the United States. The initiatives success, however, hinges on using multiple stocking locations in Mexico and bolstering binational collaboration.Impact statement