Commercially and ecologically valuable forage species selectively use shallow nearshore habitats at fine spatiotemporal scales
Date
2025
Authors
Gregr, Isabel R.
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Abstract
Nearshore ecosystems provision food and habitat for a diverse community of resident and migratory species, that in turn support coastal fisheries and economies. However, the spatial and temporal dynamics of habitat use by nearshore species are poorly understood in many areas as traditional underwater survey methods (e.g., SCUBA) only capture a snapshot in time, with many species difficult to observe in situ. Using timelapse cameras at six sites across two regions on a large nearshore shelf within a temperate inland sea, the Strait of Georgia, we determined community composition and the presence and abundance of forage species between 7 am and 7 pm during the summer of 2024. Timelapse images were paired with environmental data (temperature, current speed) to investigate how abiotic factors influenced dominant forage species. We quantified 16 taxa, including eight groups of forage fish. Community composition varied significantly over time and between regions, with forage species such as Clupea pallasii (Pacific herring) dominant earlier in the season and Doryteuthis opalescens (opalescent squid) dominant later, with these species being more abundant at different regions. Regional and temporal differences demonstrate that relatively small variations in environmental conditions can affect community composition, underscoring the need for fine-scale monitoring to inform site- and species-specific management. Pacific herring and opalescent squid showed distinct habitat use as the season progressed, with evidence of environmental factors influencing species distributions, particularly during spawning and juvenile stages. Increased temperature negatively influenced herring presence, while increased current had the opposite effect. Conversely, increased current negatively influenced squid presence. These findings have implications for predator-prey interactions, with the distributions of herring and squid likely influencing the presence of their predators, including salmon and rockfish. As climate change continues to alter ocean conditions, understanding how these species respond to environmental variability is essential in predicting shifts in their distributions.