The optimal stocking strategy for Yaqui Catfish

Abstract

The Yaqui Catfish Ictalurus pricei, a species 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 Ictalurus punctatus. To re‐establish populations in the United States, a binational program consisting of broodstock collection, fish propagation, stocking, and post‐stocking 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 post‐stocking 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. Our strategy involved simulating population growth using an age‐structured simulation model with varying amounts of stocking contribution rates, stocking density, and stocking frequency, and incorporating these biological data with economic information within a utility function to quantify stocking costs. The optimal strategy requires releasing Yaqui Catfish at a density of 200 ha‐1 every 5 years. This strategy excludes natural recruitment, as historically, stocked Yaqui Catfish inhabited waters that were either too small or void of habitat to induce natural spawning. However, were larger waters or waters having appropriate habitats (e.g., interstitial spaces) also stocked, it should increase natural recruitment, thereby enabling populations to become self‐sustaining and drastically reduce the reliance on hatcheries for stocking and salvaging declining populations. Our 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 to stock fish and is contingent on strengthening binational partnerships. This approach fills an important void in Yaqui Catfish re‐establishment, helping prime the successful recovery of this species.