Effects of shoreline armouring and overwater structures on coastal and estuarine fish: opportunities for habitat improvement

Abstract

Summary Nearshore ecosystems are increasingly recognized as critical habitats for fish of cultural, ecological and economic significance. These ecosystems are often densely inhabited by juvenile fish, highly productive and refuges from predation, leading ecologists to characterize them as nurseries. However, nearshore ecosystems are being transformed globally to support demands of growing coastal populations. Many shorelines are modified by armouring (e.g. seawalls, riprap) that minimizes erosion, and overwater structures (e.g. piers, docks) that facilitate waterfront use. These modifications affect the ecology of nearshore systems by restructuring, eliminating and shading shallow waters. Here, we review literature examining effects of armouring and overwater structures on coastal and estuarine fishes, and discuss how research and management can coordinate to minimize negative effects. Along armoured shorelines, fish assemblages differed from unarmoured sites, fish consumed less epibenthic and terrestrial prey, beach spawning was less successful and fish were larger. Under large overwater structures, visually oriented fish were less abundant and they fed less. Shade from overwater structures also interrupted localized movements of migratory fish. Thus, shoreline modifications impaired habitats by limiting feeding, reproduction, ontogenetic habitat shifts from shallow to deeper waters and connectivity. Research suggests that restoring shallow waters and substrate complexity, and minimizing shading underneath overwater structures, can rehabilitate habitats compromised by shoreline modifications. Synthesis and applications. Shoreline armouring and overwater structures often compromise fish habitats. These threats to nearshore fish habitats will become more severe as growing coastal populations and rising sea levels increase demands for shoreline infrastructure. Our ability to assess and rehabilitate nearshore fish habitats along modified shorelines will be enhanced by: focusing research attention on metrics that directly indicate fish habitat quality; implementing and evaluating shoreline features that repair compromised habitat functions within human‐use constraints; collating natural history knowledge of nearshore ecosystems; and embracing the socio‐ecological nature of habitat improvements by educating the public about conservation efforts and fostering appreciation of local nearshore ecosystems. Actions to reduce impacts of shoreline modifications on fish are particularly feasible when they align with societal goals, such as improving flood protection and providing spaces that facilitate recreation, education, and connections between people and nature.

Impact of multiple stressors on juvenile fish in estuaries of the northeast Pacific

“…Our novel findings build upon regional field studies, experimental manipulation, meta-analyses, models, reviews, and studies focusing on a single stressor or species over broad spatial and temporal components that have shown stressors can threaten fishes (Barcel o et al, 2016;Cheng et al, 2015;Crain et al, 2008;Harborne et al, 2017;Hughes et al, 2015;Minello, Able, Weinstein, & Hays, 2003;Munsch, Cordell, & Toft, 2017;Vinebrooke et al, 2004;Vye et al, 2015). Our novel findings build upon regional field studies, experimental manipulation, meta-analyses, models, reviews, and studies focusing on a single stressor or species over broad spatial and temporal components that have shown stressors can threaten fishes (Barcel o et al, 2016;Cheng et al, 2015;Crain et al, 2008;Harborne et al, 2017;Hughes et al, 2015;Minello, Able, Weinstein, & Hays, 2003;Munsch, Cordell, & Toft, 2017;Vinebrooke et al, 2004;Vye et al, 2015).…”

“…These associations are well appreciated among estuarine biologists, but broad landscape patterns have often been based more on expert knowledge (Monaco et al, 1990) than on quantitative information across systems. We can also reduce land cover stress by minimizing impervious surfaces, particularly shoreline armoring that degrades coastal fish habitats (Munsch et al, 2017). In contrast, marine fish, such as English sole, spawn in coastal areas, thus associations favor higher salinities.…”

“…Impacts of stressors and restoration actions are two areas of study deserving more attention as to their specific contributions to nursery functions (Munsch et al, 2017). Impacts of stressors and restoration actions are two areas of study deserving more attention as to their specific contributions to nursery functions (Munsch et al, 2017).…”

Fish‐smart seawalls: a decision tool for adaptive management of marine infrastructure

“…This is likely due to the creation of intensely dark environments, which can reduce prey availability, impair visual‐based behaviors, and constrain movement (Munsch et al . ). Marine infrastructure can be dominated by a few groups of fish (eg Rilov and Benayahu ) and often does not have the same assemblage of fishes in comparison to natural reefs (eg Burt et al .…”

Kelp Forest Zooplankton, Forage Fishes, and Juvenile Salmonids of the Northeast Pacific Nearshore

“…; Munsch et al. ). Our ability to conserve nearshore ecosystems in the face of these anthropogenic stressors will be improved by a nuanced and detailed understanding of how habitat attributes contribute to the development and survival of fish (Sheaves et al.…”