Effects of mesoscale structures on the distribution of cephalopod paralarvae in the Gulf of California and adjacent Pacific

Abstract

24Vertical distribution of the cephalopod paralarvae was investigated in relation to a system 25 of two cyclonic and three anticyclonic eddies in the southern Gulf of California and a front 26 in the adjacent Pacific Ocean. Results showed that the preferential habitat for the 27 Sthenoteuthis oualaniensis -Dosidicus gigas "SD-complex" in both regions was the 28 oxygenated surface mixed layer and the thermocline. The highest abundances occurred in 29 of one of the anticyclonic eddies and a frontal zone, which are convergent structures. 30 Enoploteuthid and Pyroteuthid paralarvae both displayed their highest abundances in the 31 thermocline. Pyroteuthids dominated in the cyclonic eddy whereas Enoploteuthidae were 32 less evident in the eddy system. Pyroteuthids were observed on the western (California 33 Current) side of the frontal zone, and Enoploteuthids on its eastern (Gulf of California) 34 side. The octopods and the complex of Ommastrephes-Eucleoteuthis-Hyaloteuthis 35 paralarvae were present below the thermocline. Both groups had a scarce presence in the 36 eddy system and high abundance near the frontal zone. The octopods abounded on the 37 eastern side in association with the low dissolved oxygen concentrations (< 44 µmol kg -1 ) 38 of Subtropical-Subsurface Water; the complex on the western front side was immersed in 39California Current Water. It may be concluded that the spawning and early stages of 40 development of these cephalopod groups are associated with particular mesoscale structures 41 of the water masses. For example, the "SD complex" inhabits the surface water masses, 42 preferentially in convergence zones generated by mesoscale activity. 43 44

Larval Fish Habitats and Deoxygenation in the Northern Limit of the Oxygen Minimum Zone off Mexico

“…In oceanic regions where dissolved oxygen is already low, such as the shallow oxygen minimum zones (OMZs) of the eastern North Pacific Ocean (Cepeda‐Morales et al, ; Schmidtko et al, ; Stramma et al, ), the deoxygenation process can affect the habitat of pelagic organisms from zooplankton to top predators (Diaz & Rosenberg, ; Ekau et al, ; Hofmann et al, ; Longhurst, ; Prince & Goodyear, ). Previous studies in this shallow OMZ (Fernandez‐Alamo & Farber‐Lorda, , Sánchez‐Velasco et al, , 2017, Ruvalcaba‐Aroche et al, ) reported that the zooplankton biomass and total larval fish and cephalopod paralarvae had the highest abundances in the oxygenated surface layer (>44 μmol/kg) and decreased toward the hypoxic (<44 μmol/kg) and suboxic (<4.4 μmol/kg) conditions of the deeper layers. This is similar to findings on the vertical distribution of zooplankton in other shallow OMZs in the southeastern Pacific, Benguela and Angola Currents, and the Arabian Oceans (Madhu et al, , Ekau & Verheye, , Escribano et al, , Hirche et al, ).…”

“…On the basis of previous studies that described latitudinal dissolved oxygen gradients from SE to NW (Cepeda‐Morales et al, ; Davies et al, ; Ruvalcaba‐Aroche et al, ) and the marine ecoregions defined according to species distribution (Santamaría‐del‐Ángel et al, ), the dissolved oxygen profiles were divided into two regions: the north zone located at the mouth of the Gulf of California and the south zone off Cabo Corrientes (Figure a). Particularly, the northwest conductivity, temperature and depth (CTD) stations (between 20.5°N and 23°N) are considered part of the north zone according to the Gulf of California marine ecoregion mentioned above.…”

“…The annual average depth of the 44 and 4.4 μmol/kg oxypleths and the vertical distance between these oxypleths were calculated, as well as the temperature and salinity of the 4.4 μmol/kg oxypleth in each region through the time series (see details of the data in supporting information S1). The selection of oxypleths was made on the basis of previous studies in this region (e.g., Davies et al, , Sánchez‐Velasco et al, , Sánchez‐Velasco et al, , Ruvalcaba‐Aroche et al, ). A conceptual model shows an example of the CTD profile with the oxypleths used to define the hypoxic and suboxic layers (Figure ).…”

“…The loss of dissolved oxygen in OMZs may have severe implications at the species level because critical survival thresholds may be surpassed (Schmidtko et al, ; Vaquer‐Sunyer & Duarte, ; Wishner et al, ), particularly for zooplanktonic organisms like fish larvae and cephalopod paralarvae, which are highly sensitive to dissolved oxygen changes (Koslow et al, ; Kreiner et al, ; Ruvalcaba‐Aroche et al, ). Understanding the consequences of sustained deoxygenation for taxa in the planktonic life stage in OMZs is a challenge due to the lack of knowledge of how different species respond to suboxic conditions.…”

Functional traits explain trophic allometries of cephalopods

“…The dominant members of this cephalopod community are abundant in the temperate and tropical global oceans (Bower et al., 1999; Brodeur & Yamamura, 2005; Judkins, Vecchione, Cook, & Sutton, 2017; Lischka, Piatkowski, & Hanel, 2017; Reid, 2016; Ruvalcaba‐Aroche et al., 2018; Voss, 1980) and broadly represent the diversity of activity levels exhibited by cephalopods in oceanic ecosystems. To further validate and expand the applicability of this functional approach of community trophic structure will require testing in additional ecosystem types.…”