Reviewing the Potential for Behavioral Guidance to Improve Downstream Passage of Out‐Migrating Anguillid Eels

Hydroelectric dams and their turbine infrastructure threaten out‐migrating anguillid eels en route to marine spawning grounds. For decades, invested parties have attempted to guide eels away from turbines and toward safe passage routes. A subset of this work (hereafter behavioral guidance) has involved exploiting sensory biology (e.g., sight and hearing) to divert eels from areas of danger toward safe passage, including collection facilities for trap and transport. Here, we narratively review these efforts and interpret available information through an applied lens. We collated relevant literature and organized it based on behavioral guidance modalities of light, sound, hydrodynamics, and electricity. Combined (multimodal) approaches were categorized under the primary behavioral stimulus. With further research, light could have some degree of potential as a standalone method, but field evidence indicates it is more practically effective when paired with physical barriers. Sound alone may not be sufficient, but flume evidence indicates it can also increase the effectiveness of physical barriers. Current evidence to support manipulation of hydrodynamics as a means to alter eel behavior is limited, and responses may vary considerably according to the nature of the manipulation. Electrical fields can be hazardous to downstream‐swimming eels, though they generally do elicit behavioral effects. Given our current understanding, it is apparent that multimodal approaches, particularly light and sound to augment physical barriers, are likely the most realistic for achieving reliable and effective behavioral guidance. Future research could refine knowledge in this area. It is important to continue to scale promising methods to the field to assess practical relevance.