Combined climate- and prey-mediated range expansion of Humboldt squid (Dosidicus gigas), a large marine predator in the California Current System

Abstract

Climate-driven range shifts are ongoing in pelagic marine environments, and ecosystems must respond to combined effects of altered species distributions and environmental drivers. Hypoxic oxygen minimum zones (OMZs) in midwater environments are shoaling globally; this can affect distributions of species both geographically and vertically along with predator-prey dynamics. Humboldt (jumbo) squid (Dosidicus gigas) are highly migratory predators adapted to hypoxic conditions that may be deleterious to their competitors and predators. Consequently, OMZ shoaling may preferentially facilitate foraging opportunities for Humboldt squid. With two separate modeling approaches using unique, long-term data based on in situ observations of predator, prey, and environmental variables, our analyses suggest that Humboldt squid are indirectly affected by OMZ shoaling through effects on a primary food source, myctophid fishes. Our results suggest that this indirect linkage between hypoxia and foraging is an important driver of the ongoing range expansion of Humboldt squid in the northeastern Pacific Ocean.

Vertical Migratory Behavior of Jumbo Flying Squid (<i>Dosidicus gigas</i>) off Peru: Records of Acoustic and Pop-up Tags

“…The deep-water dive pattern was also occasionally observed in the CCS and the GOC (Stewart et al 2013). In the pattern of upper layer migration, however, the depth layer (150-200 m) in the present study was shallower than in the GOC (200-400 m; Gilly et al 2006, Stewart et al 2013) and CCS where the depth (about 500 m) at which the squid spend the most time had somewhat higher oxygen concentrations than those in the OMZ proper (Stewart et al 2014). This difference in depth may be caused by latitudinal variation regarding the vertical position and thickness of the OMZ between the Southern and Northern Hemispheres.…”

Responses of Marine Organisms to Climate Change across Oceans

“…Climate change will alter the seasonal and temporal extent of areas favorable to reproduction, growth and survival for marine species (e.g., Shoji et al, 2011). Species may respond directly to changes in temperature and other climatic variables and also indirectly through changes in food and habitat resources (Stewart et al, 2014;Sydeman et al, 2015). Most marine species are ectothermic, so physiological functions are directly impacted by changes in ambient temperatures and other environmental variables (Pörtner and Knust, 2007;Pörtner and Peck, 2010).…”

Metabolic suppression during protracted exposure to hypoxia in the jumbo squid,Dosidicus gigas, living in an oxygen minimum zone

“…If oxygen has contributed to D. gigas' range expansion into the California Current, it is likely driven by indirect effects on the night-time distributions of prey species into shallower water where the prey, like the squid, must return each night. The prey may be compressed between low oxygen and high temperature into a zone that provides high-density foraging opportunities for these squid (Koslow et al, 2011;Stewart et al, 2014). While D. gigas are extremely flexible predators and may benefit from climate change (Hoving et al, 2013), they may be intolerant of the synergistic effects of either low oxygen or ocean acidification with high temperatures (Rosa and Seibel, 2008;Alegre et al, 2014).…”

“…The typical daily behavior of D. gigas involves vertical migrations from near-surface waters at night to mesopelagic depths (~300 m) during the daytime (Gilly et al, 2006;Zeidberg and Robison, 2007;Matteson et al, 2009;Stewart et al, 2013;Stewart et al, 2014). Recent work confirms that these squid are capable of remaining active at night, maintaining routine metabolism and activity levels down to a critical oxygen partial pressure (P crit ) of 1.6 kPa at 10°C (~10% air saturation) (Trueblood and Seibel, 2013;Gilly et al, 2006).…”

“…Recent interest in D. gigas is motivated, in part, by its poleward range expansion, which may be associated with warmer periods following El Niño/La Niña events and changing ecosystem interactions including food availability, competition and predation (Zeidberg and Robison, 2007). However, some recent studies have suggested a link, whether direct or indirect, between the squid's range expansion and the ongoing deoxygenation in the Eastern Pacific (Stewart et al, 2014;Rosa et al, 2013). Throughout much of the Eastern Tropical Pacific, seawater P O 2 declines with depth, from air saturation (~21 kPa) near the surface to less than 5% (<1 kPa) at intermediate depths (~250-800 m).…”