Invader's portrait: Biological characteristics of walleye pollock Gadus chalcogrammus in the western Chukchi Sea

Shifts in the composition and distribution of Pacific Arctic larval fish assemblages in response to rapid ecosystem change

“…Fossheim et al (2015) reported a similar decline of the Atlantic Arctic adult fish assemblage in the northern Barents Sea in response to a rapid influx of warmer water, predatory species from the south (e.g., Atlantic cod [ Gadus morhua ] and haddock [ Melanogrammus aeglefinus ]). In this study, Arctic cod—the most abundant fish in the Pacific Arctic (De Robertis et al, 2017; Logerwell et al, 2018) and the primary prey for many upper trophic level marine predators (Watson & Divoky, 1972; Welch et al, 1992)—decreased in larval abundance as in situ water temperatures and predatory boreal species such as pollock (Emelin et al, 2022) increased, mirroring observations of declining adult populations in the Atlantic Arctic (Eriksen et al, 2015; Hop & Gjøsæter, 2013). Due to their small size and limited swimming ability, planktonic fish larvae are more vulnerable to predation, competition, and disruptions to their zooplankton prey field compared to later life stages that are capable of directed movement toward more favorable conditions.…”

“…In all years, a warm water‐associated boreal assemblage composed primarily of yellowfin sole, whitespotted greenling, capelin, masked greenling, and pollock dominated the nearshore portions of the northern Bering and southern Chukchi seas. These taxa have primarily boreal distributions concentrated in the North Pacific Ocean and eastern Bering Sea (Mecklenburg et al, 2018), and although some boreal species (including pollock and yellowfin sole) may move northward in summer via warm surface water masses (Barber et al, 1997; Emelin et al, 2022), the cold bottom water temperatures of the Chukchi Sea have historically not been considered suitable spawning or feeding habitat for many of these species (Hollowed et al, 2013; Norcross et al, 2010). The boreal larval fish assemblage closely mirrored the distribution of warm water masses (i.e., warm Coastal Water and Shelf Water) that originate from the Bering shelf and regularly intrude into the Chukchi Sea via the Alaska Coastal Current, yet are typically restricted to the nearshore regions of the eastern Chukchi Sea.…”

“…the northern Bering and southern Chukchi seas. These taxa have primarily boreal distributions concentrated in the North Pacific Ocean and eastern Bering Sea (Mecklenburg et al, 2018), and although some boreal species (including pollock and yellowfin sole) may move northward in summer via warm surface water masses (Barber et al, 1997;Emelin et al, 2022), the cold bottom water temperatures of the Chukchi Sea have historically not been considered suitable spawning or feeding habitat for many of these species (Hollowed et al, 2013;Norcross et al, 2010). The boreal larval fish assemblage closely mirrored the distribution of warm water masses (i.e., warm…”