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Cao J.,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 7 more authors.
Scientia Marina | Year: 2011

Generalized linear Bayesian (GLBM) non-hierarchical and hierarchical models were developed for standardization of catch per unit effort (CPUE). The GLBM containing the covariates of month, latitude, sea surface temperature (SST), sea surface salinity (SSS) and sea level height (SLH) had the best fit for the Chinese squid-jigging fishery of Ommastrephes bartramii in the northwest Pacific Ocean based on deviance information criteria. This best-fitting model tends to be more ecologically sound than other CPUE standardization models, such as generalized linear models and generalized additive models. GLBM was also used to deal with the problems of estimating stock abundance index (i.e. standardized CPUE) resulting from increased spatial heterogeneity of spatial dynamics of fishing efforts in the squid fishery by predicting the standardized CPUE for unfished areas. The standardized CPUE based on data including predicted CPUE of unfished areas was lower than the derived CPUE based on data with observed CPUE alone, in particular during the fishing peak of August to October. This study indicates that it is more appropriate to use the standardized CPUE derived from data including both predicted CPUE of unfished areas and observed CPUE of fished area as a stock abundance index. We suggest that the proposed method be used in CPUE standardization to account for impacts of large spatial heterogeneity of fishing efforts in fisheries.

Liu B.,Shanghai Ocean University | Liu B.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Liu B.,University of Maine, United States | Liu B.,Collaborative Innovation Center for National Distant Water Fisheries | And 5 more authors.
Fisheries Research | Year: 2015

We explored an approach to using morphological variables of suqid body and beaks to identify different geographic populations for Dosidicus gigas. We tested this approach using a total of seventeen morphological variables of body and beaks measured for 1490 squids sampled outside the exclusive economic zone (EEZ) waters off Ecuador, Peru and Chile. Linear regression analysis showed significant and positive relationships between beak morphometric variables and mantle lengths. All measured beak variables were significantly different among the three regions (p<. 0.001), with samples from the areas off Chile and Ecuador having the largest and smallest beaks, respectively. The morphometrics of squid beaks showed a significant sexual dimorphism and were useful for sex determination (p<. 0.001), although considerable overlaps were found in the scatter-plots. Hard structure (i.e., beaks) variables were shown more effective than soft body in population discrimination, although a stepwise discriminant analysis (SDA) suggested that both the body and beak morphometric variables are useful for the geographic population discrimination. We found that the standardized beak and body variables are more effective in separating D. gigas potentially geographic populations than the original variables. © 2014 Elsevier B.V.

Liu B.,Shanghai Ocean University | Liu B.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Chen X.,Shanghai Ocean University | Chen X.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | And 5 more authors.
Marine Biology | Year: 2013

We applied the solution-based inductively coupled plasma mass spectrometry to quantify trace elements in statoliths of Humboldt squid, Dosidicus gigas, collected from the high seas off Chile, Peru, and Costa Rica by Chinese squid jigging vessels during 2007-2009. All squid samples were aged and their spawning dates were back-calculated based on daily increments in statoliths. The most abundant trace elements in the whole statolith were Ca and Sr followed by other elements in the order of Fe, Mg, Zn, Ba, Cu, Mn, Ni, Al, Cr, Co, and U. Significant differences in Mn and Sr were found among samples from the three regions. Sr, Ni, Mn, and Co contributed significantly to the discrimination among the regions, with Co responsible for explaining most of the variation, followed by Ni, Mn, and Sr. Squid from the high seas off Costa Rica could be separated from those off Peru and Chile mostly due to the differences in Ni, Sr, and Co, while samples off Peru and Chile could be distinguished mainly because of differences in Mn and Co. Discriminant function analysis suggested that the overall cross-validated classification rate was 85.6 % with samples off Chile having the highest correct identification rates and samples off Costa Rica having the highest false classification rates. Significant positive relationships were found between sea surface temperature (SST) and Cr/Ca, Mn/Ca, and U/Ca, and there was a negative relationship between SST and Cu/Ca, Sr/Ca. This study suggests that the spatial difference in trace elements of statolith can be used to separate geographic populations of D. gigas and that elements having significant relationships with SST can be considered as natural indicators of ambient temperature. © 2013 Springer-Verlag Berlin Heidelberg.

Liu B.L.,Shanghai Ocean University | Liu B.L.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Liu B.L.,Collaborative Innovation Center for Distant water Fisheries | Liu B.L.,University of Maine, United States | And 4 more authors.
Fisheries Oceanography | Year: 2015

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. © 2015 John Wiley & Sons Ltd.

Liu B.,Shanghai Ocean University | Liu B.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Chen X.,Shanghai Ocean University | Chen X.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | And 7 more authors.
Chinese Journal of Oceanology and Limnology | Year: 2013

Age, maturation and population structure of the Humboldt squid Dosidicus gigas were studied based on random sampling of the Chinese jigging fishery off the Peruvian Exclusive Economic Zones (EEZ) during 2008-2010. Estimated ages ranged from 144 to 633 days, confirming that the squid is a short-lived species with longevity no longer than 2 years. Occurrence of mature females and hatching in each month indicated that Humboldt squid spawned year-round. Back-calculated hatching dates for the samples were from January 22nd, 2008 to April 22nd, 2010 with a peak between January and March. Two size-based and two hatching date-based populations could be defined from mantle length (ML) at maturity and back-calculated hatching dates, respectively. Females matured at a larger size than males, and there was a significant difference in ML at maturity between the two hatching groups (P <0. 05). The waters adjacent to 11°S off the Peruvian EEZ may be a potential spawning ground. This study shows the complexity of the population structure and large variability in key life history parameters in the Humboldt squid off the Peruvian EEZ, which should be considered in the assessment and management of this important resource. © 2013 Chinese Society for Oceanology and Limnology, Science Press and Springer-Verlag Berlin Heidelberg.

Zhu J.,Shanghai Ocean University | Zhu J.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Zhu J.,University of Maine, United States | Xu L.,Shanghai Ocean University | And 7 more authors.
Scientia Marina | Year: 2012

The objective of this study was to estimate depth distribution of pelagic species captured in a longline fishery and to evaluate the difference in depth distribution among species. We estimated depth distribution for 17 frequently captured species based on a Chinese longline fishing trip targeting bigeye tuna (Thunnus obesus) in the central-eastern Pacific Ocean in February-November 2006. The depth distributions of 13 bycatch species were significantly different from that of bigeye tuna. Although most of the bycatch species were found to be distributed in water depths shallower than bigeye tuna (i.e. increasing hook depths can decrease catch rates of these species), the rates of catch rates declined with increasing hook depths may be different. The depth distributions were found to be not significantly different between genders for 7 species. There was no significant correlation between fish sizes and capture depths. The information derived from this study can play an important role in reducing bycatch in pelagic tuna longline fisheries in the central-eastern Pacific Ocean.

Tong Y.,Shanghai Ocean University | Tong Y.,Hainan Provincial Fisheries Research Institute | Xinjun C.,Shanghai Ocean University | Xinjun C.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | And 2 more authors.
Scientia Marina | Year: 2013

Bigeye tuna (Thunnus obesus) support a large commercial fishery in the Indian Ocean. However, explicit management strategies and harvest control rules are yet to be developed for the management of this fishery. We used a stochastic age-structured production model as an operating model to evaluate several potential management strategies under different assumptions of stock productivity. Five management strategies-constant fishing mortality, constant catch, quasi-constant catch, constant escapement, and status-dependent strategies-were evaluated and compared using the performance indicators including average catch, average spawning stock biomass, variation in catch, average fishing mortality and lowest biomass during the time period considered in the simulation. This study shows that (1) for the constant catch strategy, an annual catch of 90000 t would result in a low risk of stock being overfished while obtaining a stable catch; (2) for the constant fishing mortality strategy fishing mortality of 0.3 per year could yield a higher catch, but might have a high probability (64%) of stock dropping below the spawning stock biomass (SSB) that could achieve maximum sustainable yield (SSBmsy); and (3) for the quasi-constant catch strategy an annual catch of 110000 t was sustainable if the current SSB was higher than SSBmsy. Constant escapement and status-dependent strategies were robust with respect to different levels of virgin recruitment and steepness. This study suggests that it is important to incorporate uncertainties associated with key life history, fisheries and management processes in evaluating management strategies.

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.

Gong C.,Shanghai Ocean University | Chen X.,Shanghai Ocean University | Chen X.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Gao F.,Shanghai Ocean University | And 2 more authors.
Journal of Ocean University of China | Year: 2012

Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwestern Pacific Ocean as an example, we evaluated the impact of different weighting schemes on the HSI models based on sea surface temperature, gradient of sea surface temperature and sea surface height. We compared differences in predicted fishing effort and HSI values resulting from different weighting. The weighting for different habitat variables could greatly influence HSI modeling and should be carefully done based on their relative importance in influencing the resource spatial distribution. Weighting in a multi-factor HSI model should be further studied and optimization methods should be developed to improve forecasting squid spatial distributions. © 2012 Science Press, Ocean University of China and Springer-Verlag Berlin Heidelberg.

Li Y.-K.,Shanghai Ocean University | Li Y.-K.,National Engineering Research Center for Oceanic Fisheries | Li Y.-K.,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources
Chinese Journal of Applied Ecology | Year: 2014

With the rapidly increasing use of stable isotope analysis (SIA) in ecology, it becomes a powerful tool and complement to traditional methods for investigating the trophic ecology of animals. Sharks play a keystone role in marine food webs as the apex predators and are recently becoming the frontier topic of food web studies and marine conservation because of their unique characteristics of evolution. Recently, SIA has recently been applied to trophic ecology studies of shark species. Here, we reviewed the current applications of SIA in shark species, focusing on available tissues for analyzing, standardized analytical approaches, diet-tissue discrimination factors, diet shift investigation, migration patterns predictions and niche-width analyses, with the aim of getting better understanding of stable-isotope dynamics in shark biology and ecology research.

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