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Signatures of trace elements and isotopes in the parts of hard structures formed in the early ontogenetic stages can be used as potential natural tags of adult cephalopods to trace their origins. The Jumbo flying squid, Dosidicus gigas, is widely distributed in the eastern Pacific Ocean. Fourteen detected elemental signatures (7Li, 23Na, 24Mg, 39K, 43Ca 55Mn, 59Co, 60Ni, 63Cu, 66Zn, 88Sr, 137Ba, 208Pb and 238U) were determined in the nuclear zone (N), representing the embryonic stage, and the postnuclear zone ( PN), representing the paralarval stage of statoliths for adult D. gigas collected off the Costa Rican, Peruvian and Chilean Exclusive Economic Zones ( EEZs) using laser ablation inductively coupled plasma mass spectrometry ( LA- ICP- MS). All measured signatures were significantly different between embryonic and paralarval statoliths, except for Sr, Ba and Pb. Over the three regions, a significant difference was found for Na and Ba within embryonic statoliths and Zn and Ba within paralarval statoliths. A high Ba/Ca ratio in statoliths obtained from Costa Rica was because of the prevalence of strong upwelling in the area. Elemental signatures, especially Ba/Ca, in early ontogenetic statoliths could be used as a proxy for distinguishing different geographical groups and identifying natal origins. However, elemental signatures in embryonic statoliths tended to be a better natural tag than those in paralarval statoliths indicating that paralarvae with the same origin had distinct dispersal pathways. Additionally, stepwise discriminant analysis ( SDA) showed there were at least two migration-based groups: 'northern' and 'southern' in the eastern Pacific Ocean. Overall, the derived results can improve our knowledge of the population structure, connectivity and life history of D. gigas. [ABSTRACT FROM AUTHOR]

Based on the investigation data of 44 stations in the area 28°－35° N, 147°－154° E of the Northwestern Pacific Ocean by the research ship 'Songhang' in March 2019, we analyzed species composition and distribution of zooplankton to understand zooplankton community structure in the subtropical areas of the Northwestern Pacific Ocean. The results showed that a total of 456 zooplankton species (including planktonic larvae and unidentified species) were recorded in the surveyed area, which were belonged to 8 categories and 14 groups. There were 163 species of copepods, as the dominant group. The dominant species included 9 warm-water species, Eudoxoides spiralis , Neocalanus gracilis , Pleuromamma gracilis , Sagitta enflata , Doliolum nationalis , S. hexaptera, Euchirella rostrata , Nannocalanus minor and Mesocalanus tenuicornis, and one temperate species, Calanus jashnovi. Both the warm current indicator species S. hexaptera and the cold current indicator species C. jashnovi occurred simultaneously in the subtropical area, indicating that the Kuroshio Current and the Oyashio Current had an important impact on the diversity and temporal-spatial distribution of marine zooplankton. The average biomass was (31.64±23.81) mg·m -3 , and the average abundance was (22.2±17.6) ind·m -3 . The average values of purity index ( C ), eveness index ( J ), Shannon diversity index ( H ) and richness index ( D ) were 0.09±0.10, 0.76±0.10, 4.88±0.71, and 23.53±8.08, respectively. The spatial distribution of the four indices were uneven and irregular. During the study period, species composition of zooplankton in the Northwest Pacific was rich, species distribution was uneven, and community structure was stable.

Dosidicus gigas is widely distributed in the Eastern Pacific Ocean and plays an important role in the marine ecosystem. In this study, we identified and analyzed 4131 otoliths and 75 beaks from the stomach content residuals of 62 D. gigas samples, which were collected by Chinese squid jigging vessels in the high sea of Eastern Pacific Ocean from June to December 2019. The results showed that the preys of D. gigas included 10 fish species and 4 cephalopod species. Judging from the frequency of appearance and percentage of amount, Vinciguerria lucetia , Diogenichthys laternatus , and Triphoturus mexicanus were the dominant myctophidae prey of D. gigas . Among those preys, V. lucetia was the most important one, as it was found in all D. gigas with different mantle lengths. D. gigas , Sthenoteuthis oualaniensis , and Onychoteuthis banksii were the dominant cephalopod prey. With the growth of mantle length of D. gigas , the number of prey species, the percentage of cephalopod and myctophidae preys, and the size of preys increased, and thus the trophic level of preys increased as the trophic pattern of preys changed. Our results could provide basic information for evaluating the contribution of different preys in the preying transformation of D. gigas .