Subtidal shellfish reefs as fish habitats within urban coastal seascapes of Gulf St. Vincent, South Australia
In Gulf St. Vincent near metropolitan Adelaide, South Australia, researchers compared fish assemblages across restored oyster reefs, natural pinnid reefs, seagrass and bare sediment. Unbaited video surveys revealed distinct assemblages in each habitat, with seagrass supporting the highest fish abundance. Structural habitats—both restored and natural—hosted richer, behaviorally diverse fish communities than bare sediment. These findings highlight the ecological value of shellfish reefs and demonstrate a multi‑metric approach that strengthens fish‑habitat monitoring for restoration and seascape management.
Subject Tags
- Reefs
- Coastal
- Habitat restoration
Abstract
Interest in coastal management is increasing globally, particularly in urbanized temperate regions where cumulative stressors have degraded biogenic habitats. This includes renewed shellfish reef conservation efforts including restoration and fish habitat management. However, fish-habitat interactions within and across shellfish reefs and habitat types, including taxonomic, behavioural and trait variability, is understudied. Here, we investigated subtidal shellfish reef fish assemblages in Gulf St. Vincent near metropolitan Adelaide, South Australia, from restored oyster (Ostrea angasi) and natural pinnid (Pinna bicolor) reefs, in comparison to seagrass and bare sediment habitats. Fishes were surveyed with unbaited video stations and were analyzed using multiple assemblage metrics. All habitats were found to support distinct fish assemblage compositions, with the highest fish abundances associated with seagrass meadows. Across structural habitats of shellfish reef and seagrass habitats, fish assemblages shared similar traits, behaviours and higher species richness compared to bare sediment habitats. These findings indicate that both restored and natural shellfish reefs can support distinct fish assemblages and reaffirms the fish habitat value of structural habitats. By investigating fish-habitat interactions using multiple fish assemblage metrics, we demonstrate an approach that expands knowledge of shellfish reef fish monitoring that is applicable to other restoration and seascape management efforts.
Citation
Martin, B., Huveneers, C., Reeves, S., & Baring, R. (2025). Subtidal shellfish reefs as fish habitats within urban coastal seascapes of Gulf St. Vincent, South Australia. Transactions of the Royal Society of South Australia, 149(2), 242-264. https://doi.org/10.1080/03721426.2025.2536885
TNC Authors
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Simon Reeves
The Nature Conservancy