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

Brad Martin , Charlie Huveneers , Simon Reeves, Ryan Baring

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 aimed to assess nekton assemblage variation associated with an oyster reef restoration site, within an anthropogenically modified estuary as a case study. 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. Nekton assemblages were strongly influenced by interannual effects, with few outcomes 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. Outcomes were influenced by environmental variables with distinct seasonal effects. Implications Restoration structures can provide functionally redundant nekton habitats in urban estuaries characterised by pre-existing artificial structures, at least in the early stages prior to upscaled restoration. Restoration practitioners must consider environmental conditions and community composition in anthropogenically modified environments.

MF24179  Accepted 19 March 2025

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