North Pacific warming shifts the juvenile range of a marine apex predator

Abstract

During the 2014–2016 North Pacific marine heatwave, unprecedented sightings of juvenile white sharks (Carcharodon carcharias) emerged in central California. These records contradicted the species established life history, where juveniles remain in warmer waters in the southern California Current. This spatial shift is significant as it creates potential conflicts with commercial fisheries, protected species conservation, and public safety concerns. Here, we integrate community science, photogrammetry, biologging, and mesoscale climate data to describe and explain this phenomenon. We find a dramatic increase in white sharks from 2014 to 2019 in Monterey Bay that was overwhelmingly comprised of juvenile sharks < 2.5 m in total body length. Next, we derived thermal preferences from 22 million tag measurements of 14 juvenile sharks and use this to map the cold limit of their range. Consistent with historical records, the position of this cold edge averaged 34° N from 1982 to 2013 but jumped to 38.5° during the 2014–2016 marine heat wave. In addition to a poleward shift, thermally suitable habitat for juvenile sharks declined 223.2 km2 year−1 from 1982 to 2019 and was lowest in 2015 at the peak of the heatwave. In addition to advancing the adaptive management of this apex marine predator, we discuss this opportunity to engage public on climate change through marine megafauna.

Range edges of North American marine species are tracking temperature over decades

“…Sessile invertebrates are particularly vulnerable to dispersal limitation if prevailing currents do not align with local climate velocities, as in the Northeast (Fuchs et al, 2020;Molinos et al, 2017). On the West Coast, threshold responses to nonlinear temperature change may also structure species distributions; El Niño events sometimes cause the transport of anomalously warm water up the coastline, facilitating transient poleward range extensions of species-some of which have persisted after these warm events ended (Leising et al, 2015;Tanaka et al, 2021;Zacherl et al, 2003). The Eastern Bering Sea system's high degree of edge thermal niche tracking may be partly due to sea ice causing fairly stable winter temperatures there (Stabeno et al, 2001).…”

Dynamic Thermal Corridor May Connect Endangered Loggerhead Sea Turtles Across the Pacific Ocean

“…Oceanographic conditions are expected to become more extreme with climate change, leading to shifts in the distributions and migratory pathways of sea turtles, sea birds, marine mammals, and pelagic fishes (Hazen et al, 2012b). If a thermal corridor across the Eastern Pacific Barrier were to open more frequently in a warming ocean, it may result in an increase in the relative abundance of loggerheads and other highly migratory marine megafauna shifting from the Central North Pacific to foraging grounds along the eastern Pacific coast (e.g., Pacific bluefin tuna (Kitagawa et al, 2007), white sharks (Tanaka et al, 2021), and northern elephant seals (Abrahms et al, 2018). Finally, a change in the distribution of protected species can pose increased conservation challenges.…”

Narrowing the niche of shark fin harvests in the global ocean

“…For coastally restricted species such as C. amblyrhynchos and S. tudes, public databases provide validated empirical observations in novel marine regions. Subjectively censoring such data sources falsely assumes that species ranges are either fixed or already perfectly understood [24]. For widespread pelagic species such as I. oxyrinchus and I. paucus , most extra-range observations are adjacent the ERM, perhaps reflecting more recent poleward expansions from ocean warming [24,25].…”

“…Subjectively censoring such data sources falsely assumes that species ranges are either fixed or already perfectly understood [24]. For widespread pelagic species such as I. oxyrinchus and I. paucus , most extra-range observations are adjacent the ERM, perhaps reflecting more recent poleward expansions from ocean warming [24,25]. Figure 1 c crops our SDM output for I. paucus with its corresponding ERM, emphasizing the structure of habitat preferences the SDM provides that is missing from the comparatively flat ERM.…”