Capture–translocation restores spawning migration connectivity of Razorback Suckers in the fragmented San Juan River

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AbstractObjectiveBarriers to movement negatively affect population vital rates of riverine fishes that rely on connected migratory routes to complete components of their life cycle, such as reproduction and recruitment. In the southwestern United States, decades of water diversion, construction of large impoundments, and loss of floodplain habitats have all contributed to highly fragmented riverscapes. A capture–translocation strategy was implemented for Razorback Suckers Xyrauchen texanus in the San Juan River to mitigate the negative effects of two barriers while precluding the upstream movement of nonnative species. We hypothesized that translocated individuals would remain upstream of barriers during the spawning season and that aggregations of translocated Razorback Suckers would be identified upstream in spawning habitats.MethodsWe used radiotelemetry to assess movement of Razorback Suckers after translocation above the two barriers. We deployed fixed remote radio receivers to determine residency time above each barrier and conducted mobile telemetry surveys to monitor upstream destinations after translocation.ResultAlthough most Razorback Suckers returned downstream of barriers within 2 months of translocation, we provide evidence that most individuals remained upstream long enough to successfully spawn. After translocation above the Piute Farms Waterfall, 80% of individuals remained upstream for 26 days in 2020 and for 23 days in 2021. Further upstream (307 km), at a weir operated by the Public Service Company of New Mexico, 80% of translocated individuals remained above the barrier for 37 days in 2021 and for 25 days in 2022. After fish translocation above both barriers, we observed upstream movements ranging from 2 to 262 km and we detected distinct aggregations within the expected spawning season.ConclusionAlthough translocation efforts seasonally reconnect migratory routes for a proportion of the population and may increase spawning potential, other conservation actions are likely still needed to improve recruitment conditions for juvenile fish.