Documenting Changes in Fish Passage and Ecological Connectivity Following Low‐Head Dam Removal: Challenges and Opportunities in a Mid‐Size River

ABSTRACT Demolition and removal of aging dam structures is increasingly common as a part of river restoration efforts, with anticipated benefits for re‐establishing connectivity among river biota and habitats. We studied fish movement behavior in the vicinity of a run‐of‐river, low‐head dam before and after its removal. Radio telemetry was used to track the movement of smallmouth bass and determine if movement past the dam site increased following removal. We also conducted a translocation experiment to confirm that habitat structure and flow conditions at the restored site did not impede passage. Movement of radio‐tagged smallmouth past the dam site was moderately different following dam removal, with a minor improvement in upstream passage. Results of translocation experiments indicated that the dam remnant site did not impede passage, as the return rate of fish translocated past the dam was comparable to homing behavior observed in previous studies. We hypothesize that technological constraints combined with ontogenetic patterns in smallmouth bass spatial ecology reduced our likelihood of observing individual dispersal. In systems lacking migratory (e.g., diadromous) species, research to document the effects of dam removal on fish movement and connectivity must consider how ontogenetic variation in movement behavior may limit our ability to observe and document ecological outcomes. A combination of approaches is likely to be most effective for studying non‐migratory species responses to dam removal. Experimental translocation can be effective for confirming short‐term improvements in fish passage, though other methods are more appropriate for documenting ecological benefits to fish populations and communities over longer timescales.