Divergent responses of highly migratory species to climate change in the California Current

Abstract

AimMarine biodiversity faces unprecedented threats from anthropogenic climate change. Ecosystem responses to climate change have exhibited substantial variability in the direction and magnitude of redistribution, posing challenges for developing effective climate‐adaptive marine management strategies.LocationThe California Current Ecosystem (CCE), USA.MethodsWe project suitable habitat for 10 highly migratory species in the California Current System using an ensemble of three high‐resolution (~10 km) downscaled ocean projections under the Representative Concentration Pathway 8.5 (RCP8.5). Spanning the period from 1980 to 2100, our analysis focuses on assessing the direction and distance of distributional shifts, as well as changes in core habitat area for each species.ResultsOur findings reveal a divergent response among species to climate impacts. Specifically, four species were projected to undergo significant poleward shifts exceeding 100 km, and gain habitat (~7%–60%) in response to climate change. Conversely, six species were projected to shift towards the coast, resulting in a loss of habitat ranging from 10% to 66% by the end of the century. These divergent responses could typically be characterized by the mode of thermoregulation (i.e. ectotherm vs. endotherm) and species' affiliations with cool and productive upwelled waters that are characteristic of the region. Furthermore, our study highlights an increase in niche overlap between protected species and those targeted by fisheries, which may lead to increased human interaction events under climate change.Main ConclusionsBy providing valuable species distribution projections, our research contributes to the understanding of climate change effects on marine biodiversity and offers critical insight and support for developing climate‐ready management of protected and fished species.

Marine heatwaves redistribute pelagic fishing fleets

“…Vessels may reallocate fishing effort into alternative management areas, and the higher concentrations of vessels may increase fishing pressure on targeted species and potentially generate greater competition among fishers (Ojea et al, 2020). Extreme events and climate-driven ecosystem change Lezama-Ochoa et al, 2023) in both of these regions have also exacerbated human-wildlife conflicts, such as greater interaction risks with protected or vulnerable species (Davies & Brillant, 2019;Samhouri et al, 2021). For example, the delayed opening of the Dungeness Crab fishery in California coincided with the onshore compression of productive whale foraging habitat, intensifying the spatial overlap of whales and crab fishing gear, and resulted in an alarming rise in blue and humpback whale entanglements (Santora et al, 2020).…”

“…Identified core fishing grounds were a subset of suitable habitat and this classification was used to ensure that regions with a low probability of fishing effort occurrence did not bias results and that we are only capturing fishing grounds vessels will likely act on (Hazen et al, 2013;White et al, 2019). We explored the sensitivity of multiple threshold values on our fleet response metrics (Table S2, Figures S4 and S5), which resulted in defining core fishing grounds as the average top 75th percentile of suitability values across mapped spatial predictions for each fleet (Hazen et al, 2013(Hazen et al, , 2018Lezama-Ochoa et al, 2023;White et al, 2019)…”

Northeast Atlantic elasmobranch community on the move: Functional reorganization in response to climate change

“…where j is the year considered, a Hs;i is the area of the spatial cell i in km 2 calculated using the "area" function of the "raster" R package, Hs i is the habitat suitability in the cell, and N is the total number of cells. This weighted calculation limits threshold selection bias and is a more conservative approach, given the different range of habitat suitability between species (Lezama-Ochoa et al, 2023;Rubenstein et al, 2023).…”

“…Population-level changes in response to climate change have also been observed in recent decades, such as changes in the range and/or migratory timing of the Tiger Shark (Hammerschlag et al, 2022), or increased use of breeding habitat by the Bull Shark (Bangley et al, 2018) and White Shark (Tanaka et al, 2021). Future shifts are also expected for the 21st century, with both gains and losses of suitable habitats depending on the species (e.g., Grieve, et al, 2020, andrequiem andmackerel sharks, Birkmanis et al, 2020;Diaz-Carballido et al, 2022;Lezama-Ochoa et al, 2023).…”