Demersal fish predators of gelatinous zooplankton in the Northeast Pacific Ocean

Abstract

Historically, gelatinous zooplankton have been considered important consumers or predators in marine food webs, but more recently they have also been recognized as important prey for many marine species. Here, we summarized data obtained from >100 Northeast Pacific fish predators based on extensive gut content analysis (~450000 stomachs examined) from broad-scale demersal trawl surveys ranging from the Bering Sea to Southern California. In the Bering Sea, we identified 27 predators on jellyfish and 23 on urochordates. In the Aleutian Islands, 14 and 18 predators were identified, respectively, and for the Gulf of Alaska, a total of 23 and 32 such predators were documented. Off the West Coast of the contiguous USA, we identified 16 coelenterate predators and 7 urochordate predators. Many of these predators were not previously known to prey on gelatinous zooplankton. Dominant consumers of coelenterates include prowfish, rockfishes, walleye pollock, sablefish, and grenadiers, and primary consumers of urochordates included rockfishes, Atka mackerel, and sablefish. Pronounced seasonal and interannual variability in gelatinous taxa occurrence was observed in several dominant fish predators. The occurrence of jellyfish prey was generally much higher in diets of fishes examined fresh at sea when compared with diets of the same species examined in the laboratory following preservation. Differences in occurrence were less pronounced with the more durable urochordate prey. We suggest that many existing estimates of predation on easily dissolved gelatinous prey may underestimate the true predation rate and the importance of these organisms in marine food webs.

Trophic ecology of yellowtail rockfish (Sebastes flavidus) during a marine heat wave off central California, USA

“…Gelatinous zooplankton (i.e., tunicates) were of greater dietary importance to the populations of S . flavidus in our study than previously noted [ 10 , 12 , 13 , 41 ], and the incorporation of pyrosomes into the prey spectrum was a novel finding. Since 2013, and likely initiated by rising sea surface temperatures and northward flow of subtropical waters, the abundance of the most common tunicates captured in pelagic trawl surveys in the California Current (i.e., Thetys vagina , Pyrosoma atlanticum ) has increased markedly [ 42 ].…”

“…Gelatinous zooplankton are known to be a prey source for many fish species in the northeast Pacific [ 41 ], but the overall importance in food webs is often underrepresented. One reason for this is because gelatinous zooplankton abundance may not be adequately represented in stomach samples due to a more rapid digestion process or sampling methods.…”

“…One reason for this is because gelatinous zooplankton abundance may not be adequately represented in stomach samples due to a more rapid digestion process or sampling methods. Previous studies have shown that S. flavidus tend to consume larger abundances of gelatinous zooplankton when available in their habitat [12,41]. Knowing the role that environmental factors and changing ocean conditions play on the availability of this prey category influences our understanding of predator feeding strategy and energy transfer throughout the food web.…”

DNA metabarcoding reveals the importance of gelatinous zooplankton in the diet ofPandalus borealis, a keystone species in the Arctic

“…The taxonomic identification of diet items can be time‐consuming and introduce bias due to varying experience of the investigating expert as well as the state of digestion of the prey (Nielsen et al, 2018; Sheppard & Harwood, 2005; Wangensteen et al, 2011). Moreover, the dietary contribution of soft‐bodied prey items such as jellyfish and other gelatinous zooplankton can be strongly underestimated with SCA (Brodeur et al, 2021; Hays et al, 2018; McInnes et al, 2017; Sheppard & Harwood, 2005) because they are more rapidly digested than hard‐bodied prey (Hays et al, 2018). Consequently, dietary regime shifts in an ecosystem may remain undetected (McInnes et al, 2017).…”

Distribution and diversity of gelatinous zooplankton in the southern South China Sea

“…GZ comprises diverse marine organisms, including medusae, siphonophores, appendicularians, chaetognaths, pteropods, salps, and doliolids. They represent one of the driving forces of marine ecosystems [2], as their components undergo seasonal pulses in response to favourable conditions and produce biomass rapidly that can sustain the marine pelagic food webs [3][4] and increase deep carbon transfer efficiently [5][6]. Hence, they play an important role in marine trophic webs and structuring coastal and estuarine ecosystems [7].…”