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Lin D.,Shanghai Ocean University | Lin D.,Collaborative Innovation Center for National Distant Water Fisheries | Chen X.,Shanghai Ocean University | Chen X.,Collaborative Innovation Center for National Distant Water Fisheries | And 6 more authors.
Invertebrate Biology | Year: 2015

Energy investment in reproduction and somatic growth was investigated for summer spawners of the Argentinean shortfin squid Illex argentinus in the southwest Atlantic Ocean. Sampled squids were examined for morphometry and intensity of feeding behavior associated with reproductive maturation. Residuals generated from length-weight relationships were analyzed to determine patterns of energy allocation between somatic and reproductive growth. Both females and males showed similar rates of increase for eviscerated body mass and digestive gland mass relative to mantle length, but the rate of increase for total reproductive organ weight relative to mantle length in females was three times that of males. For females, condition of somatic tissues deteriorated until the mature stage, but somatic condition improved after the onset of maturity. In males, there was no correlation between somatic condition and phases of reproductive maturity. Reproductive investment decreased as sexual maturation progressed for both females and males, with the lowest investment occurring at the functionally mature stage. Residual analysis indicated that female reproductive development was at the expense of body muscle growth during the immature and maturing stages, but energy invested in reproduction after onset of maturity was probably met by food intake. However, in males both reproductive maturation and somatic growth proceeded concurrently so that energy allocated to reproduction was related to food intake throughout the process of maturation. For both males and females, there was little evidence of trade-offs between the digestive gland and reproductive growth, as no significant correlation was found between dorsal mantle length-digestive gland weight residuals. The role of the digestive gland as an energy reserve for gonadal growth should be reconsidered. Additionally, feeding intensity by both males and females decreased after the onset of sexual maturity, but feeding never stopped completely, even during spawning. © 2015 The American Microscopical Society. Source

Fang Z.,Shanghai Ocean University | Fang Z.,Collaborative Innovation Center for Distant Water Fisheries | Xu L.,Shanghai Ocean University | Xu L.,Collaborative Innovation Center for Distant Water Fisheries | And 14 more authors.
Fisheries Science | Year: 2015

Cephalopod beaks maintain a stable morphology, implying that they can be used to explore ecological influences on squid life history. Understanding the beak growth pattern can help us to improve knowledge of the trophic characteristics of squids and to estimate squid biomass. Sthenoteuthis oualaniensis is widely distributed in eastern tropical Pacific equatorial waters and has been caught commercially by Chinese squid jigging fleets since 2011. In this study, we randomly took 220 samples of S. oualaniensis with mantle lengths (ML) of between 119 and 351 mm and body weights (BW) of between 45 and 1975 g and measured six beak morphological variables for each sampled squid. The relationships between ML and all of the beak variables were power functions, except for upper lateral wall length (ULWL), upper crest length, and lower lateral wall length, which showed linear relationships with ML. The relationships between BW and the six beak variables were best fitted with power functions, and these functions can be used to estimate squid biomass from beak variable values. All of the beak morphological variables varied according to the maturity stage of the squid. Results of a post hoc comparison suggested that the values of beak morphological variables for immature squids (maturity stages I and II) showed significant differences from the corresponding values for mature squids (maturity stages III–V). These differences may result from changes in diet that occur during maturation, which affect the relevant mandibular muscle strength. The most common pigmentation stages (PS) encountered were II–V. The relationships of PS to ULWL and lower wing length were best described by exponential functions. Beak morphology and pigmentation of S. oualaniensis tended to change markedly with ontogenetic stage. It is easy to separate mature and immature squids based on their PS. This study provides important biological information on S. oualaniensis. © 2015, Japanese Society of Fisheries Science. Source

Chen X.,Shanghai Ocean University | Chen X.,The Key Laboratory of Shanghai Education Commission for Oceanic Fisheries Resources Exploitation | Tian S.,Shanghai Ocean University | Tian S.,The Key Laboratory of Shanghai Education Commission for Oceanic Fisheries Resources Exploitation | And 4 more authors.
Chinese Journal of Oceanology and Limnology | Year: 2011

The eastern fall cohort of the neon flying squid, Ommastrephes bartramii, has been commercially exploited by the Chinese squid jigging fleet in the central North Pacific Ocean since the late 1990s. To understand and identify their optimal habitat, we have developed a habitat suitability index (HSI) model using two potential important environmental variables - sea surface temperature (SST) and sea surface height anomaly (SSHA) - and fishery data from the main fishing ground (165°-180°E) during June and July of 1999-2003. A geometric mean model (GMM), minimum model (MM) and arithmetic weighted model (AWM) with different weights were compared and the best HSI model was selected using Akaike's information criterion (AIC). The performance of the developed HSI model was evaluated using fishery data for 2004. This study suggests that the highest catch per unit effort (CPUE) and fishing effort are closely related to SST and SSHA. The best SST- and SSHA-based suitability index (SI) regression models were SI SST-based = 0.7SI effort-SST + 0.3 SI CPUE-SST, and SI SSHA-based = 0.5SI effort-SSHA + 0.5SI CPUE-SSHA, respectively, showing that fishing effort is more important than CPUE in the estimation of SI. The best HSI model was the AWM, defined as HSI=0.3SI SST-based+ 0.7SI SSHA-based, indicating that SSHA is more important than SST in estimating the HSI of squid. In 2004, monthly HSI values greater than 0.6 coincided with the distribution of productive fishing ground and high CPUE in June and July, suggesting that the models perform well. The proposed model provides an important tool in our efforts to develop forecasting capacity of squid spatial dynamics. © 2011 Chinese Society for Oceanology and Limnology, Science Press and Springer-Verlag Berlin Heidelberg. Source

Chen X.,Shanghai Ocean University | Chen X.,The Key Laboratory of Shanghai Education Commission for Oceanic Fisheries Resources Exploitation | Tian S.,Shanghai Ocean University | Tian S.,The Key Laboratory of Shanghai Education Commission for Oceanic Fisheries Resources Exploitation | And 4 more authors.
Fishery Bulletin | Year: 2010

We developed a habitat suitability index (HSI) model to understand and identify the optimal habitat and potential fishing grounds for neon flying squid (Ommastrephes bartramii) in the Northwest Pacific Ocean. Remote sensing data, including sea surface temperature, sea surface salinity, sea surface height, and chlorophyll-a concentrations, as well as fishery data from Chinese mainland squid fleets in the main fishing ground (150-165°E longitude) from August to October, from 1999 to 2004, were used. The HSI model was validated by using fishery data from 2005. The arithmetic mean modeling with three of the environmental variables-sea surface temperature, sea surface height anomaly, and chlorophyll-a concentrations-was defined as the most parsimonious HSI model. In 2005, monthly HSI values >0.6 coincided with productive fishing grounds and high fishing effort from August to October. This result implies that the model can reliably predict potential fishing grounds for O. bartramii. Because spatially explicit fisheries and environmental data are becoming readily available, it is feasible to develop a dynamic, near real-time habitat model for improving the process of identifying potential fishing areas for and optimal habitats of neon flying squid. Source

Liu B.,Shanghai Ocean University | Chen X.,Shanghai Ocean University | Chen X.,The Key Laboratory of Shanghai Education Commission for Oceanic Fisheries Resources Exploitation | Chen X.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | And 6 more authors.
Scientia Marina | Year: 2010

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°30'W-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°30'-41°S and 78°30'-80°W and by 25°-30°S and 76°-77°30'W. 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. Source

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