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  • Using Fish Behavior to Assess Habitat Quality of a Restored Oyster Reef
  • Craig A. Layman (bio), Zachary R. Jud (bio), D. Albrey Arrington (bio), and David Sabin (bio)

Human activities in the coastal realm have led to drastic declines in population sizes of marine organisms (Lotze et al. 2006). Of particular concern have been declines in foundation species (e.g., oysters, seagrasses, and coral) that form the structural basis for ecosystems and are associated with numerous ecosystem processes that we highly value. Oyster reefs, for instance, provide habitat for other fishery species, enhance water quality, sequester carbon, and stabilize shorelines; economic valuations suggest the sum of these ecosystems services may total $99,000/hectare/year (Grabowski et al. 2012). Despite this significant value, oyster population declines have been substantial, e.g., oyster biomass declined by 88% in U.S. coastal waters between the early 1900s and early 2000s (Ermgassen et al. 2012).

Restoration projects are increasingly being implemented to stem or reverse these declines. Although many oyster reef restorations are designed to increase production for commercial purposes, another important goal is to reestablish the multiple ecosystem services that are supported by living oyster reefs. In the context of coastal fishery declines (Lotze et al. 2006), of particular interest is the efficacy of oyster reef restoration projects for augmenting populations of economically and ecologically important fish and invertebrate species. New fish production is likely supported by restored oyster reefs (Peterson et al. 2003), although precise estimates of increased fishery yields are difficult to quantify. In fact, simply assessing the extent that nekton utilize restored oyster reefs can be difficult, due to the relatively small size of many restored reefs within a heterogeneous seascape, temporal dynamics in species abundance, and the challenges associated with sampling transient fauna in structurally complex habitat (Grabowski et al. 2005).

Here we provide an alternative perspective to assess the success of oyster reef restorations in the context of fishery ecology, namely using the behavior of individual fish to [End Page 140] reflect habitat quality. We utilize acoustic telemetry to quantify fish movement patterns in a patch habitat before and after an oyster restoration project, with the a priori assumption that increased residence time of individuals within a habitat patch is related to the quality of that habitat (Lindell 2008).

The study was conducted in the Loxahatchee River (26°57' N, 80°06' W), a 27-kilometer-long coastal river that flows into the Atlantic Ocean near Jupiter, Florida, USA. Oyster reefs have been significantly degraded in the system, largely as a result of anthropogenic alteration of salinity. The section of river where salinities presently favor oyster growth is substrate limited, with a benthos composed largely of sand and silt that lacks settlement habitats for larval oysters. In 2008, the Loxahatchee River District and The Nature Conservancy initiated a community-based oyster reef restoration program. The goal of this project was to create new oyster reef habitat in the substrate-limited section of river by deploying bags of dried oyster shell and Reef BallsTM (Reef Ball Foundation, Inc., Athens, GA, USA) under privately owned residential docks (Figure 1).

This fish movement study was conducted at one of the restoration docks, located in the northwest fork of the river approximately 6km from the ocean (26°58.038'N, 80°07.192W). In this section of the river, the entire shoreline is developed, and now consists of bulkheads and docks. As such, the main structurally complex habitats available (before the restoration project) were dock pilings and scattered rip-rap under docks; no significant oyster reefs or other natural habitat types (mangroves) were present along this shoreline. In October 2008, the restoration reef was constructed by adding a continuous layer of bagged oyster shell (150 black duronet diamond mesh bags, 33 cm wide, 19 mm mesh; DelStar Technologies, Inc., Middletown, DE, USA) under the dock (Figure 1). To provide additional surface area for oyster recruitment, 15 Reef Balls were placed under the deepest portion of the dock. A total of ~37m2 of substrate were covered with the oyster bags and Reef Balls™. Following restoration, recruitment of sessile (e.g., oyster spat) and motile benthic organisms (e.g., small crustaceans) to...

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