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Nuanced influences of subtidal artificial shellfish structures on nekton communities in urbanised estuaries

Published Article

South Australia

Publication date: April 9, 2025

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Urban estuaries increasingly use reef installations to restore ecological function, yet early outcomes for nekton remain unclear. This study monitored nekton communities before and 14 months after oyster‑reef restoration in the Port River–Barker Inlet estuary, comparing results with a control site. Thirty‑four species were detected, with harvestable nekton comprising over 60% of abundance. Assemblages were influenced primarily by interannual and seasonal environmental variation, with few direct restoration effects and increased use of structures by non‑native gobies. Findings suggest that small‑scale reef trials may be functionally limited in heavily modified estuaries until larger spatial and functional changes are achieved.

Subject Tags

  • Estuary
  • Habitat restoration
  • Reefs

Abstract

Context

Reef installation is increasingly considered for urbanised estuaries to enhance and restore ecological functions. Restoration structures are expected to provide nekton habitat benefits, but early outcomes are poorly understood.

Aims

This study assessed nekton assemblage variation associated with an oyster reef restoration site, situated within the anthropogenically modified Port River–Barker Inlet estuary.

Methods

Nekton communities and environmental variables were measured 6 weeks before, and 14 months following restoration, and at a control site. Modelling was used to assess spatio-temporal variation.

Key results

Video monitoring detected 34 species, with harvestable nekton comprising 60.3% of total abundances. Nekton assemblages were strongly influenced by interannual effects, with few outcomes being directly related to restoration activities. Restoration structures supported non-native gobies during the study.

Conclusions

These results suggest that small-scale restoration can have little detectable impact on urbanised fish communities in the early stages of estuarine restoration. Nekton were influenced by environmental variables with distinct seasonal variation.

Implications

In urban estuaries characterised by pre-existing artificial structures, small trial oyster reefs may be functionally redundant as nekton habitats until sufficient spatial-scale and functional changes are achieved.

Citation

Martin, B., Huveneers, C., Reeves, S., & Baring, R. (2025). Nuanced influences of subtidal artificial shellfish structures on nekton communities in urbanised estuaries. Marine and Freshwater Research, 76(6), MF24179. https://doi.org/10.1071/MF24179

TNC Authors

  • Simon E. Reeves
    The Nature Conservancy