Chen, X. J., Zhao, X. H., and Chen, Y. 2007. Influence of El Niño/La Niña on the western winter–spring cohort of neon flying squid (Ommastrephes bartramii) in the northwestern Pacific Ocean. – ICES Journal of Marine Science, 64: 1152–1160. Ommastrephes bartramii is an oceanic squid distributed widely in the North Pacific, and its western winter–spring cohort is the target of a traditional squid fishery. Commercial fisheries data from the Chinese mainland squid-jigging fleet for the period 1995–2004 were analysed with respect to environmental variables. Sea surface temperature anomalies (SSTA) in the Niño 3.4 region had the strongest negative correlation with the SSTA of feeding and spawning grounds of the squid, with a time-lag of three and eight months (p < 0.05), respectively. A La Niña event would result in a decrease in squid recruitment through variability in environmental conditions on the spawning grounds, whereas an El Niño event would lead to environmental conditions favourable to squid recruitment. El Niño/La Niña events also influenced squid distribution on the feeding grounds, resulting in a northward shift of the fishing grounds in La Niña years and a southward shift in El Niño years. A multiple linear regression equation was derived to describe the dependence of the squid abundance index on environmental variables.

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counting methods used are reliable. This study suggests that the RSS of the upper beak is an appropriate tool for estimating the age of D. gigas, O. bartramii and perhaps S. oualaniensis, although erosion of the rostral region may result in an underestimation of squid ages.

The age, growth and maturation of the purpleback flying squid, Sthenoteuthis oualaniensis, were determined by statolith analysis using data from April–June 2013 surveys in the equatorial eastern tropical Pacific Ocean (ETPO). Three distinct growth zones with different width increments (postnuclear, dark and peripheral zones), checks and aberrant microstructures were found in the statoliths. The longevity of the species was a maximum of 0.5 years. Hatching dates were from November to March, with a peak between January and February. The high percentage of mature females (69.5%) suggested that there was at least another peak after April–June, and the study area might be a potential spawning ground for the species. Size and age at first maturity were 192-mm mantle length (ML) and 114 days for females, whereas males began to mature at 137mm ML and 87 days.

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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.

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