Marine reserves indirectly affect fine‐scale habitat associations, but not overall densities, of small benthic fishes

Abstract

Many large, fishery‐targeted predatory species have attained very high relative densities as a direct result of protection by no‐take marine reserves. Indirect effects, via interactions with targeted species, may also occur for species that are not themselves targeted by fishing. In some temperate rocky reef ecosystems, indirect effects have caused profound changes in community structure, notably the restoration of predator–urchin–macroalgae trophic cascades. Yet, indirect effects on small benthic reef fishes remain poorly understood, perhaps because of behavioral associations with complex, refuge‐providing habitats. Few, if any, studies have evaluated any potential effects of marine reserves on habitat associations in small benthic fishes. We surveyed densities of small benthic fishes, including some endemic species of triplefin (Tripterygiidae), along with fine‐scale habitat features in kelp forests on rocky reefs in and around multiple marine reserves in northern New Zealand over 3 years. Bayesian generalized linear mixed models were used to evaluate evidence for (1) main effects of marine reserve protection, (2) associations with habitat gradients, including complexity, and (3) differences in habitat associations inside versus outside reserves. No evidence of overall main effects of marine reserves on species richness or densities of fishes was found. Both richness and densities showed strong associations with gradients in habitat features, particularly habitat complexity. In addition, some species exhibited reserve‐by‐habitat interactions, having different associations with habitat gradients inside versus outside marine reserves. Two species (Ruanoho whero and Forsterygion flavonigrum) showed stronger positive associations with habitat complexity inside reserves. These results are consistent with the presence of a behavioral risk effect, whereby prey fishes are more strongly attracted to habitats that provide refuge from predation in areas where predators are more abundant. This work highlights the importance of habitat structure and the potential for fishing to affect behavioral interactions and the interspecific dynamic attributes of community structure beyond simple predator–prey consumption and archetypal trophic cascades.

The effect of motorboat sound on Australian snapper Pagrus auratus inside and outside a marine reserve

“…For example, fish in the protected site are free from fishing and are known to exhibit bolder or more fearless behavior when confronted with recreational divers. However, fish outside the protected area are under both commercial and recreational fishing pressure and may have evolved or learned to be more cautious when detecting human intrusions (Cole, 1994; Smith & Anderson, 2016). This behavior is mirrored by reactions to motorboat sound where protected snapper remain in the area and continue feeding, whereas fish outside the protected area either leave the area or decrease feeding activity.…”

Influence of habitat condition on shallow rocky reef fish community structure around islands and headlands of a temperate marine protected area

“…Through selectivity by individuals seeking shelter and/or food, species may associate with certain habitat types such that changes in habitat quality and quantity translate to variations in fish distribution and abundance across the seascape (Coleman et al 2016, Fulton et al 2016. Benthic habitat formers, such as canopy-forming macroalgae, seagrass, sponges and corals, create key habitats that support juvenile and adult reef fish spe-cies (Teixeira-Neves et al 2015, Smith & Anderson 2016, van Lier et al 2017, Wilson et al 2017. With habitat loss affecting both conservation and harvest use of our coastal areas, there is a strong need to understand the role of habitat condition to facilitate and enhance fish biodiversity, abundance and replenishment (Rodwell et al 2003, Noble et al 2013).…”