Variable spatial management implications based on different seabird distribution and diversity metrics

As resource managers strive to balance marine ecosystem health and services with diverse ocean uses, the spatial and temporal dynamics of species distributions-and their overlap with both static and dynamic human activities-should be carefully considered. Anthropogenic activities and management decisions rarely affect only one species, underscoring the need for spatially and seasonally resolved, multispecies approaches to inform conservation prioritization for effective marine spatial planning. We conducted at-sea visual surveys for seabirds using strip transect methods during spring, summer, and fall in the Northern California Current over 2 years (2022-2024). Using this dataset, we developed density surface models to describe and predict the seasonal distribution and density of the 22 most abundant seabird species. We then applied spatial clustering to identify seasonal hotspots and coldspots of three distinct metrics: (1) seabird density, (2) species diversity, and (3) relative abundance of conservation-priority species. To demonstrate management implications associated with using each of these metrics, we evaluated how hotspots and coldspots overlapped with proposed offshore wind energy areas and seasonal commercial fishing activity. Hotspots and coldspots differed both spatially and seasonally, depending on the metric used to construct them. For example, some locations simultaneously supported a density coldspot and a diversity hotspot, and others were a coldspot for conservation-priority species in spring but a hotspot in summer. Notably, there were no locations where hotspots defined by all three metrics overlapped. Though this study is not an impact assessment, our results have implications for marine spatial planning. In particular, multispecies metrics associated with abundance and diversity may have contrasting implications for spatial management strategies, necessitating careful a priori identification of management objectives. Our study illustrates how hotspots and coldspots can be used to evaluate potential conflicts between marine species and static (offshore wind development areas) and dynamic (seasonal fishing activity) human uses of marine regions. The choice of metrics to define hotspots and coldspots can shape conclusions about conflict or compatibility between species conservation and human use of marine resources.