Designing, implementing and monitoring the translocation of a highly threatened freshwater fish

Abstract

Abstract Conservation translocations are increasingly applied for the protection of threatened species, but their success depends strongly on pre‐release preparatory work and strict implementation methodology, followed by post‐release monitoring. The aim of this work was to implement a conservation translocation that involved (a) the design and application of a pre‐release feasibility assessment tool for the selection of the translocation water bodies; (b) the translocation of 77 individuals of the highly threatened freshwater Corfu killifish Valencia letourneuxi in 2015, 2016 and 2017; and (c) a 5‐year post‐release monitoring with multiple methods. After initial pre‐screening, a feasibility assessment was conducted on two potential release water bodies (R‐WBs) and on four potential source water bodies (S‐WBs), using a custom‐made feasibility assessment tool that incorporated 14 criteria for the potential R‐WBs, related to the species' habitat requirements, human pressures and technical issues. Two criteria were applied to the potential S‐WBs, on source population availability and on its genetic compatibility to the release area. Post‐release monitoring (2017–2022) was conducted with fish sampling methods, underwater video recording and/or using environmental DNA (eDNA). The feasibility assessment tool gave one R‐WB high, positive score, and one S‐WB met both criteria, thus these selected as the translocation water bodies. Despite the low number of founders, the establishment of a self‐reproducing population was finally confirmed in 2022 in the R‐WB, initially with video recording and subsequently by fish sampling and eDNA. This study highlights the importance of pre‐release feasibility assessment, the use of multiple post‐release monitoring methods and actions to secure the long‐term viability of the translocated population. The feasibility assessment tool and the methodological protocol can easily be modified for successful application to other freshwater fish species, with different habitat requirements, current and future human pressures and genetic constraints.