Multi‐Species Fish Habitat Preferences for Various Modified Concrete Armouring Designs to Enhance Shoreline Biodiversity

ABSTRACT Human actions, such as the construction of concrete retaining walls as a form of shoreline armouring, pose an increasing threat to freshwater ecosystems. Conventional concrete armouring methods frequently result in habitat homogenization, which has a detrimental effect on aquatic biodiversity. This laboratory study examined the habitat preferences of four fish species (Yellow Perch [ Perca flavescens ], Bluegill [ Lepomis macrochirus ], Banded Killifish [ Fundulus diaphanus ] and Rock Bass[ Ambloplites rupestris ]) experimentally introduced to three types of concrete armouring treatment panels with different surface relief depths (5.08 cm, 7.62 cm and 10.16 cm) intended to create structural complexity paired with a flat wall control panel in 20 min dichotomous choice behavioural assays. We found that both species and treatment had a significant impact on space use, with the proportion of time spent near the different treatment panels varying among species. Compared to the treatment panels, fish spent less time near the flat control panels on average, indicating that the treatments' increased structural complexity provided more desirable habitat. Bluegill spent more time near the treatment panels than Banded Killifish and Yellow Perch, while Rock Bass spent more time near the treatment panels than Banded Killifish. As such, future efforts to implement such armouring in the field should consider using panels with a diversity of reliefs to ensure that these structures provide benefit to a wide range of fishes. Our findings highlight the possibility of using novel concrete armouring designs as alternatives to flat retaining walls to improve habitat complexity and benefit freshwater biodiversity where armouring is required.