Global declines in oyster reefs have resulted in reduced habitat heterogeneity, extent and quality for some coastal finfish, potentially reducing fish populations and catches. It is well established that habitat restoration results in higher finfish biomass and diversity where oyster reefs replace bare substrata. Therefore, restoring oyster reefs with a view to also improving fish stocks is often a key goal of oyster restoration. However, the principles of habitat quality, ecological connectivity and broader ecosystem management are poorly integrated within oyster reef restoration ecology, but such principles may be instructive in enhancing the benefits of projects on fish populations throughout estuarine seascapes. This manuscript presents a framework for projects seeking to restore both oyster reef habitat and finfish communities. Structurally and biologically complex oyster reefs, comprising both oysters and other invertebrates, are required to provide shelter, food and nursery services to fish. By carefully considering site selection at seascape scales (km to 10s of km), restoration can enhance the network of habitat available to fish and potentially increase the overall carrying capacity of the estuary. Managers of estuaries that now include restored oyster reefs should implement fisheries management plans and consider the effects of management actions broadly throughout catchments; failing to do so may jeopardize gains in fish yields. Management decisions must be adaptable, responding to key criteria in thorough monitoring programs. Integrating these ecological and coastal management concepts into oyster reef restoration will enhance outcomes for fishes and increase stakeholder engagement and cost‐effectiveness.

The seascape context of coastal ecosystems plays a pivotal role in shaping patterns in fish recruitment, abundance, and diversity. It might also be a principal determinant in structuring the recruitment of fish assemblages to restored habitats, but the trajectories of these relationships require further testing. In this study, we surveyed fish assemblages from 14 restored oyster reefs and 14 control sites in the Noosa River, Queensland, Australia, that differed in the presence or absence of seagrass within 500 m, over four periods using baited cameras. Fish assemblages at oyster reefs differed from those at control sites, with higher species richness (1.4 times) and more individuals of taxa that are harvested by fishers (1.8 times). The presence or absence of seagrass nearby affected the abundance of a key harvestable fish species (yellowfin bream Acanthopagrus australis) on oyster reefs, but not the overall composition of fish assemblages, species richness, or the total abundance of harvestable fishes overall. These findings highlight the importance of considering species-specific patterns in seascape utilization when selecting restoration sites and setting restoration goals, and suggest that the effects of restoration on fish assemblages might be optimized by focusing efforts in prime positions in coastal seascapes.

Ecological restoration principally seeks to restore lost or degraded ecosystems. Restoration can, however, also deliver a suite of wider ecological, social, and economic benefits. To optimize performance it is, therefore, important to plan the design and placement of restoration initiatives with a view to maximizing joint effects on ecosystems, animal populations, ecological functions, and ecosystem services. We measured the effects of multiple (13) restored oyster reefs on a suite of restoration benefits (oyster settlement and growth, fish diversity and abundance, the ecological functions of scavenging and predation) in the Noosa River estuary, Australia, and used distribution models to identify potential restoration sites with the greatest overall benefits. Oysters recruited to reefs, and reefs enhanced the diversity and abundance of fishes and had higher rates of ecological functions than control sites. However, the growth of oyster reefs was most correlated with the proximity of restoration sites to urbanized shorelines and the estuary mouth, and the area of mangroves around the site. By contrast, fish diversity and abundance, and the rates of ecological functions, were typically negatively correlated with the proximity of reefs to both mangroves and seagrasses. This complex spatial mosaic resulted in distinct areas predicted to achieve all restoration benefits that were significantly smaller than the total area that could be restored. Applying a systematic and defensible method to identify potential restoration sites that maximize multiple benefits while lowering costs is a sensible social, economic, and ecological strategy.

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Restored shellfish reefs provide valuable habitat for fish, but it is not clear how different approaches affect performance, and either promote the development of new fish populations (i.e. “production”) or simply attract individuals from the broader seascape (i.e. “attraction”). We measured the effects of a 1.5 ha shellfish reef restoration site on fish assemblages in Pumicestone Passage in eastern Australia, which contains replicates of six different restoration units: shell patch reefs, crates of shells, and biodegradable matrix, and each had replicates with and without live oysters. Fish were surveyed before restoration and then every 6 months for 30 months with baited (at restoration and control sites) and unbaited (at 106 sites across the seascape to detect potential fish attraction, and at the different restoration units) underwater cameras. Shellfish reef restoration represents an addition to the carrying capacity of Pumicestone Passage for fish for two key reasons. First, restoration significantly enhanced the diversity and abundance of fish assemblages and the density of harvestable fish at the restoration site by 3.8, 10.7, and 16.4 times, respectively. Second, fish distributions across the broader seascape did not change in response to succession at the restoration site. Fish assemblages did not differ between restoration units or the presence or absence of oysters. These findings further support the notion that restored shellfish reefs significantly enhance fish abundance and diversity and that restored reefs can enhance the overall carrying capacity of seascapes for fish, rather than simply centralizing them at restoration sites.