The jumbo flying squid, Dosidicus gigas, support an important squid fishery off the Exclusive Economic Zone of Chilean waters. However, we only have limited information about their biology. In this study, age, growth and population structure of D. gigas were studied using statoliths from 533 specimens (386 females and 147 males) randomly sampled in the Chinese squid jigging surveys from 2007 to 2008 off the Exclusive Economic Zone of Chile. Mantle lengths (MLs) of the sample ranged from 206 to 702 mm, and their ages were estimated from 150 to 307 days for females and from 127 to 302 days for males. At least two spawning groups were identified, the main spawning peak tended to occur between August and November (austral spring group), and the secondary peak appeared during March to June (austral autumn group). The ML–age relationship was best modelled by a linear function for the austral spring group and a power function for the austral autumn group, and the body weight (BW)–age relationship was best described by an exponential function for both the groups. Instantaneous relative growth rates and absolute growth rates for ML and BW did not differ significantly between the two groups. The growth rate of D. gigas tended to be high at young stages, and then decreased after the sub-adult stage (>180 days old). This study suggests large spatial and temporal variability in key life history parameters of D. gigas, calling for the collection of more data with fine spatial and temporal scales to further improve our understanding of the fishery biology of D. gigas.

SUMMARY:The jumbo flying squid Dosidicus gigas is widely distributed in the eastern Pacific Ocean and supports an important fishery. Although many studies have been carried out on the biology of this species, limited biological information is available in the waters outside the Exclusive Economic Zone of Chile (EEZ) (20°S-41°S and 74°30ʹW-84°W). Three surveys were conducted in this area by the Chinese squid jigging vessels during the period from April 2006 to May 2008. The majority of the catch in the survey was from the two areas defined by 37°30ʹ-41°S and 78°30ʹ-80°W and by 25°-30°S and 76°-77°30ʹW. The sex ratio (M: F) of the catch was 1: 2.48. The mean mantle length (ML) was 376 mm for males with a range of 257-721 mm and 388.7 mm for females with a range of 236-837 mm. Two distinguished size classes, medium-and large-sized groups, were identified in this study with the medium-sized group (350-450 mm ML) consisting of 89% of the total catch. The sizes at first sexual maturity were 638 mm ML for females and 565 mm ML for males. This study suggests that all the individuals examined were hatched from March 2007 to February 2008, indicating that D. gigas might spawn all year around with a peak spawning time from November 2007 to January 2008. Most of the stomachs analyzed had food remains. The preys included three major groups: fish (mainly lanternfish), cephalopods and crustaceans, but D. gigas was the dominant species in the stomach contents, showing strong evidence of cannibalism. The information obtained from this study improves our understanding of the fishery biology of D. gigas off Chile.Keywords: Dosidicus gigas, fishery biology, Chile. RESUMEN: Biología pesquera de la pota gigante DosiDicus gigas en aguas exteriores a la Zona Económica Exclusiva de Chile. -La pota gigante Dosidicus gigas está ampliamente distribuida en el océano Pacífico oriental y soporta una pesquería importante. Aunque se han realizado muchos estudios sobre la biología de esta especie, la información existente para aguas externas a la Zona Económica Exclusiva (ZEE) de Chile (20ºS-41ºS y 74º30ʹW-84ºW) es muy limitada. Los barcos poteros chinos realizaron tres campañas en esta área entre abril de 2006 y mayo de 2008. La mayoría de las capturas en esas campañas proceden de dos áreas definidas por las coordenadas 37º31ʹS-41ºS 78º30ʹW-80ºW y 25ºS-30ºS 76ºW-77º30ʹW, respectivamente. La relación sexual (M:H) en las capturas fue de 1:2.48. La longitud media del manto (LM) fue de 376 mm para los machos con un rango que varió entre 257 y 721 mm, y de 388.7 mm para las hembras (236-837 mm). Se diferenciaron dos clases de tamaño: un grupo medio, cuya LM varió entre 350 y 450 mm representando un 89% de la captura total, y un grupo grande. La talla de primera maduración sexual fue de 638 mm para las hembras y de 565 mm para los machos. Este trabajo sugiere que todos los individuos examinados habían nacido entre marzo de 2007 y febrero de 2008, lo cual indica que D. gigas puede frezar durante todo el año, habiendo existido un pico de puesta desde n...

SUMMARY: Four oceanic squid species, Ommastrephes bartramii, Dosidicus gigas, Sthenoteuthis oualaniensis and Illex argentinus, not only support important commercial fisheries, but also play a vital role in their marine ecosystems. It is therefore important to identify them in the analyses of their predators' stomach contents as this can yield critical information on the trophic dynamics of ecosystems. Hard beaks of the four species frequently found in their predators' stomachs can be used to identify them. In this study, to remove the effect of size differences among individuals, measurements of upper and lower beaks were standardized with an allometric model. A discriminant analysis was carried out to compare morphological differences among the four species and between the sexes for each species. The upper rostral width and upper rostral length showed the greatest interspecific variation in the beak morphological variables of the four Ommastrephidae. The linear discriminant functions of beak morphological variables were developed for the four Ommastraphidae, which resulted in a rate of correct species classification of over 97%. Sexual dimorphism was also found in the beak morphology of O. bartramii and I. argentinus. This study suggests that morphological variables can be used to reliably classify Ommastrephidae at genus level, which can help identify the specie in the stomachs of cephalopod predators. This helps to improve the understanding of the role cephalopods play in their marine ecosystems. Ommastrephes bartramii, Dosidicus gigas, Sthenoteuthis oualaniensis e Illex argentinus, sometidas a una importante presión pesquera, juegan un papel significativo dentro de los ecosistemas marinos a los que pertenecen. Al ser los picos de estas especies resistentes, las medidas de diversos aspectos de su morfología pueden servir para identificarlas en análisis de contenidos estomacales de sus depredadores. Ello permite obtener una información crucial sobre la dinámica trófica de los ecosistemas. En el presente estudio, las medidas realizadas en los picos superior e inferior de los Ommastrephidae se han normalizado mediante un modelo de crecimiento alométrico, para evitar la influencia del efecto tamaño de los individuos. A continuación, mediante un análisis discriminante, se han estudiado las diferencias morfológicas entre las cuatro especies, así como entre machos y hembras. Las medidas que presentaban mayores variaciones eran la anchura y longitud del rostro superior. Mediante funciones discriminantes lineales de las medidas morfológicas normalizadas de sus picos, se han conseguido clasificar las cuatro especies de Ommastraphidae, con una fiabilidad superior al 97%. Asimismo, a través de sus medidas morfológicas, se ha encontrado un claro dimorfismo sexual en los picos de O. bartramii e I. argentinus. El presente estudio sugiere que las medidas morfológicas pueden ser útiles para clasificar correctamente los Ommastrephidae a nivel de Scientia Marina 76(3) September 2012, 473-481, Barcelona (Spain) Keywords

Ontogenetic variation in 4 trace element ( 88 Sr, 137 Ba, 24 Mg, 23 Na) concentrations and their ratios to Ca were measured in statoliths of the jumbo flying squid Dosidicus gigas off the Exclusive Economic Zone of Chilean and Peruvian waters using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The element compositions of statoliths showed no significant differences between females and males. All of the elements in different growth zones showed significant variations, except for Mg. Sr:Ca and Mg:Ca were good indicators for distinguishing squid from autumn and winter spawning seasons. Sr:Ca and Ba:Ca distribution patterns in statoliths confirmed that paralarvae and juvenile squid inhabit surface waters, while subadult squid migrate into deeper waters. An increasing Sr:Ca ratio of subadult squid could be explained by declining temperature gradients from northern to southern sampling locations, although no significant Sr:Ca differences were observed (p > 0.05). Mg:Ca ratios decreased progressively from the nucleus to the peripheral zone, which might be correlated with statolith growth rates. Na:Ca ratios slightly declined from paralarvae to the subadult phase. Quantitative relationships between statolith trace elements and environmental conditions under different growth stages are needed to improve our understanding of life history of D. gigas.

This study aimed to explore the feasibility of using an upper beak microstructure to estimate the age of purpleback flying squid (Sthenoteuthis oualaniensis). From these microstructures, the age and growth of squid caught from January to March and May to August in 2018, 2019, and 2020 in the waters surrounding the Xisha Islands in the South China Sea were determined. We found three typical growth zones (the hood region, crest region, and axis), abnormal increments (checks), and erosion in the beak examination. The average dorsal mantle length (ML) of males and females was 112.13 (±15.23 mm) and 119.67 mm (±24.50 mm), respectively, and no squid were older than 10 months. The peak hatching dates, according to back calculations, were from October to January of the next year. All sampled squid belonged to the autumn/winter cohort. Significant sex differences were found in the relationship between ML and age in squid with similar growth patterns. Exponential models best described the relationships of ML with age and body weight (BW) for both sexes. However, a linear model best described the relationship between age and upper rostrum length (URL). The maximum absolute daily growth rates (AGR) of BW were reached during days 240–270 for both sexes. The maximum AGRs in ML were reached during days 180–210 and 240–270 for males and females, respectively. The period of 120–150 days (4–5 months) was considered the sub-adult stage of S. oualaniensis in the Xisha Islands waters of the South China Sea. This study confirmed that the beak microstructure provides good age estimates for purpleback flying squid (S. oualaniensis).