Review of Methods for Sampling Fish in Structured Habitats

Structured aquatic habitats such as coral reefs, mangroves, and shipwrecks often harbor higher densities of fish than unstructured habitats, but sampling fish in structured habitats is difficult. Structured habitats can snag and damage, or be damaged by, sampling gears and provide refugia that obscure fish. Here, the diverse literature on sampling fish in structured habitats was reviewed and synthesized, focusing on the strengths and drawbacks of 24 sampling approaches that were classified as conventional, visual, acoustic, tagging, and novel methods. A number of key conclusions emerged from this review. First, no single gear can sample all fish species consistently across all structured habitats; optimal sampling gears depend on the morphology and behavior of the species, the physical characteristics of the habitat, and objectives of the study. Second, combining sampling gears provides a more complete picture of fish communities in structured habitats and, in some cases, can account for imperfect detection. Third, novel approaches like environmental DNA (eDNA), close-kin mark-recapture (CKMR), and autonomous vehicles deserve more research attention because they have the potential to revolutionize fish sampling in structured habitats. Improved sampling of fish in structured habitats will enhance fisheries management, benefiting the fish, their habitats, and those who rely on healthy fish populations.