Response of Abundance and Distribution of Humboldt Squid (Dosidicus gigas) to Short-Lived Eddies in the Eastern Equatorial Pacific Ocean From April to June 2017

Abstract

In this study, the eddy characteristics on the fishing ground of the Humboldt squid (Dosidicus gigas) in the eastern equatorial Pacific Ocean were detected based on geometrical characteristics with the flow field during April–June 2017. The influence of the eddies on the biophysical environment, D. gigas abundance, and habitat distribution were explored. The habitat was identified by fishery data, sea surface temperature (SST), vertical water temperature, and chlorophyll-a (Chl-a). Results indicated that the eddy lifetime was relatively short, with only three eddies persisting for more than 2 weeks. The number of eddies in each month showed a similar variability trend with the monthly average catch per unit effort (CPUE) of D. gigas. Two eddies were taken with a lifetime of above 2 weeks, which revealed that the environmental conditions around the eddies significantly changed. When the eddy persisted for 8–10 days, SST and vertical temperature gradually decreased, but Chl-a significantly increased. The habitat quality of D. gigas gradually increased, and the gravity center of the fishing ground was consistent with eddy movement. The eddy-induced Ekman pumping led to the transportation of deep waters with rich nutrients into the euphotic layer, promoted the reproduction of bait organisms, and yielded favorable water temperature conditions for D. gigas. These environmental changes aided the formation of high-quality habitats, which increase D. gigas abundance and catch and drive the shift of the gravity centers of fishing grounds with the eddy. Our findings suggested that eddy activities have significant impacts on D. gigas abundance and habitat distribution.

Mesoscale eddies modulate the dynamics of human fishing activities in the global midlatitude ocean

“…Meanwhile, our results indicated that the debate concerning eddy‐induced high trophic organism distribution in previous studies is largely attributed to different spatial areas. Most previous case studies supporting high trophic organisms preferring anticyclonic eddies appeared in our revealed hotspots of the midlatitude oceans, such as swordfish in the Kuroshio Extension System (Durán Gómez et al, 2020), loggerhead sea turtles in the Brazil‐Malvinas Confluence region (Gaube et al, 2017), and sharks in the Gulf Stream (Braun et al, 2019; Gaube et al, 2018), while the case studies supporting that they prefer cyclonic eddies or have no obvious preference largely appeared in the lower latitude ocean, such as loggerhead sea turtles in the East China Sea (Kobayashi et al, 2011), cetacean species and bluefin tuna in the Gulf of Mexico (Davis et al, 2002; Teo & Block, 2010), squid in the Eastern Equatorial Pacific (Fang et al, 2021), and tuna species in the Mozambique Channel (Potier et al, 2014). These previous cases can be regarded as a subset of our revealed hotspots and support our findings.…”

“…These previous cases can be regarded as a subset of our revealed hotspots and support our findings. Existing case studies usually focus on the abundance difference of high trophic organisms between anticyclonic eddies and cyclonic eddies, and comparisons between the two‐polarity eddy and outside eddy regions are absent (Arur et al, 2014; Braun et al, 2019; Durán Gómez et al, 2020; Fang et al, 2021; Gaube et al, 2018; Tew Kai & Marsac, 2010). Considering the effects of eddy‐occupied areas, our findings showed a more direct and overall relationship between mesoscale eddies and potential fish distribution by comparing the fishing activities per unit area between the anticyclonic eddy/cyclonic eddy and outside eddy regions, which provided reliable evidence that anticyclonic eddy (cyclonic eddy) regions were beneficial (detrimental) to their aggregation relative to outside eddy.…”

“…All of these results supported that the fishing efforts derived from satellite monitoring were promising as a feasible approach for investigating the spatial distribution of target fish species. Confluence region (Gaube et al, 2017), and sharks in the Gulf Stream (Braun et al, 2019;Gaube et al, 2018), while the case studies supporting that they prefer cyclonic eddies or have no obvious preference largely appeared in the lower latitude ocean, such as loggerhead sea turtles in the East China Sea (Kobayashi et al, 2011), cetacean species and bluefin tuna in the Gulf of Mexico (Davis et al, 2002;Teo & Block, 2010), squid in the Eastern Equatorial Pacific (Fang et al, 2021), and tuna species in the Mozambique Channel (Potier et al, 2014). These previous cases can be regarded as a subset of our revealed hotspots and support our findings.…”

“…Based on the bottom‐top control hypothesis from eddies to fish and fishing activities, previous studies presented an ongoing debate regarding how eddies exert impacts on high trophic organisms using the limited data available from electronic tags, commercial fishing records or voyage investigations. For example, the existing studies have reported that some high trophic organisms prefer cyclonic eddies, such as yellowfin tuna ( Thunnus albacares , Scombridae) and bigeye tuna ( Thunnus obesus , Scombridae) in the northwest Atlantic (Hsu et al, 2015), Southern elephant seal ( Mirounga leonine , Phocidae) in the Kerguelen Plateau (Bailleul et al, 2010; Dragon et al, 2010), Humboldt squid ( Dosidicus gigas , Ommastrephidae) in the Eastern Equatorial Pacific (Fang et al, 2021), and cetacean species and bluefin tuna ( Thunnus thynnus , Scombridae) in the Gulf of Mexico (Davis et al, 2002; Teo & Block, 2010), while other studies have presented the opposite viewpoint in which some high trophic organisms prefer anticyclonic eddies, such as shark species in the Gulf Stream (Braun et al, 2019; Gaube et al, 2018), king penguin ( Aptenodytes patagonicus , Spheniscidae) in the Crozet Islands (Cotté et al, 2007), and bluefin tuna in the northwest Atlantic (Hsu et al, 2015). Even for the same high trophic organisms, their relationship is debatable.…”

Changing Humboldt Squid Abundance and Distribution at Different Stages of Oceanic Mesoscale Eddies

“…Analyses of equatorial regions using the maximum entropy model have shown that D. gigas prefers to inhabit areas with relatively low eddy kinetic energy [30]. The eddy pumping induced by eddies provides abundant nutrients for D. gigas, creating high-quality habitats within the eddies [31].…”