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Wang X.-F.,Shanghai Ocean University | Xu L.-X.,Shanghai Ocean University | Xu L.-X.,Ministry of Education Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Xu L.-X.,Shanghai Higher Education Commission Key Laboratory of Oceanic Fisheries Resources Exploitation | And 4 more authors.
Chinese Journal of Applied Ecology | Year: 2010

Fish age and growth are the important biological parameters for the assessment of fishery resources. With the help of purse seiners, 262 individuals of skipjack tuna (Katsuwonus pelamis) were sampled from western and central Pacific Ocean in October 2007-January 2008. The measurements in situ showed that the fork length of the samples ranged from 278 to 746 mm, and their body mass ranged from 345 to 9905 g. The first dorsal spine of each individual was collected for age identification and growth parameters estimation. The relationship between fork length (L, mm) and body mass (M, g) was expressed as M=3.612 × 10 -6L 3.278 (R 2 =0.9782), and no significant difference was found for the males and females (F =2. 002, P>0. 05). A comparison with Akaike information criterion (AIC) suggested that among power regression equation, linear regression equation, and exponential regression equation, linear regression equation was most suitable for describing the relationship between fork length and spine radius (AIC =2257.4). The mean back-calculated fork lengths of K. pelamis with the ages of 1-5 estimated by Fraser-Lee's method were 398.4, 494.2, 555.4, 636.8, and 728.8 mm, respectively. Residual analyses indicated that there was no significant difference in the growth of male and female K. pelamis (F = 0. 670 ; df = 182; P>0. 05). The sex-combined von Bertalanffy growth equation of K. pelamis was L t =706. 51 (1-e -0.64(t+0.037).

Gong Y.,Shanghai Ocean University | Chen X.-J.,Shanghai Ocean University | Chen X.-J.,National Engineering Research Center for Oceanic Fisheries | Chen X.-J.,Ministry of Education Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | And 6 more authors.
Chinese Journal of Applied Ecology | Year: 2014

Stable isotope analysis (SIA) has become an important tool to investigate diet shift, habitat use and trophic structure of animal population. Muscle is considered to be the most common tissue for SIA, however, lipid content in muscle causes a considerable bias to the interpretation of isotopic ratios of animals. Neon flying squid (Ommastrephes bartramii) is an important economic cephalopod of Chinese distant water fishery, and plays a major role in marine ecosystems. In this study, the effects of lipid extraction on stable isotope ratios of the muscles of 53 neon flying squids were investigated and the interference mechanism of lipid in SIA was clarified with the aim of contrasting the suitability of different lipid correction models of stable carbon isotope. Results showed that the stable carbon and nitrogen isotopic values of non-lipid extracted samples significantly increased after lipid extractions by 0.71‰ and 0.47‰, respectively, which suggested that lipid extraction in cephalopod isotope study is needed prior to stable carbon isotope analysis but not recommended for stable nitrogen isotope analysis. The results could help remove the effects of lipid contents and standardize SIA muscle samples, thereby getting better understanding of the isotopic change of neon flying squids in the future. ©, 2014, Editorial Board of Chinese Journal of Applied Ecology. All right reserved.

Wang S.Q.,Shanghai Ocean University | Xu L.X.,Shanghai Ocean University | Xu L.X.,National Engineering Research Center for Oceanic Fisheries | Xu L.X.,Ministry of Education Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | And 9 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

Tropical tunas are a kind of highly migratory oceanic fishes whose food organisms in perched waters are relatively scarce and are distributed as patches. The tunas are obliged to swim quickly in response to dynamic changes of its prey because of hardly lasting aggregation of food organisms. Tropical tunas are inclined to form natural aggregations which are usually referred to as free swimming schools. In early days, however, the artisanal fisherman noted that the tropical tunas have the habit of gathering around natural floating objects such as logs, seaweed mats, branches and palm leaves, forming stable aggregations, termed as floating-objects-associated schools. They found that fishing was much efficient near these objects than in an open ocean. Tuna purse seine fisheries utilized this type of behavior to develop a great number of fish aggregation devices (FADs) for aggregating tuna and thus improve harvest efficiency. Two types of FADs are often used: drifting FADs (dFADs) and anchored FADs (aFADs). Since the first FAD deployments, FADs-based fishing technology had developed rapidly throughout the early 1990s, and FADs have been generally accepted as an effective mean to increase catch rates and reduce the energy consumption of purse seiners. The large-scale use of FADs, however, considerably increases the density of floating objects in some waters, and in turn, to some extent, artificially changes the surface habitat of the tuna. This may impose a series of potentially negative effects on tuna populations, such as changes in patterns of aggregation, feeding pattern and migratory movement and the decline of physical conditions for the population. Of those mentioned-above side effects, changes in the feeding pattern may have more profound impacts on fish populations as it exerts a direct effect on key life history processes, such as growth and reproduction. In the past 30 years, many studies have been conducted to evaluate whether and how FADs affect the feeding pattern. However, the results from these studies are still inconclusive and contradictory. This review summarizes recent studies in regard to the tuna feeding patterns as influenced by FADs. We compare differences of feeding behavior, daily rations, the types of prey and ecological niche width between FAD-associated and free swimming tuna schools. It implies that, FADs tend to alter the large-scale migratory movements to some extents, but not the local and small-scale migratory movements. FADs may also influence the stomach contains and the rates of empty stomach. Thus, FADs, in most cases, do in fact change feeding pattern and behavior. This review also identifies shortcomings in previous studies in their research methods and contents, and accordingly proposes new research approaches, such as the use of underwater video camera to observe the feeding behavior of tunas directly, take advantage of remaining stomach contents to rebuild diet composition for the estimation of the daily rations. Stable isotope analysis (SIA) can also help improve our understanding of trophic ecology for tunas. We also include a discussion on possible future research direction in evaluating impacts of FADs on feeding behavior for tunas.

Wang X.-F.,Shanghai Ocean University | Zhu G.-P.,Shanghai Ocean University | Zhu G.-P.,Ministry of Education Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources | Zhu G.-P.,Shanghai Higher Education Commission Key Laboratory of Oceanic Fisheries Resources Exploitation | And 6 more authors.
Chinese Journal of Applied Ecology | Year: 2012

Tuna prefers to aggregate around floating objects. Based on this behavioral characteristic, people developed fish aggregation devices(FADs) to trap tuna, and made the catch and fishing efficiency of tuna purse seine fisheries improved greatly. However, there still exist uncertainties whether the FADs can attract tuna and what's the potential impact of widely applying FADs in tuna purse seine fishery on tuna resources and oceanic pelagic ecosystem. Aiming at these uncertainties, scientists conducted a great deal experiments to study the behavioral biology of tuna around FADs. This paper reviewed the related classic and more credible experiments in the past 30 years, and summed up five behavioral patterns of the tunas around drifting and anchored FADs, i. e., tropism behavior, schooling behavior, association behavior, feeding behavior, and vertical movement pattern. The related main research methods currently in use were introduced, and the issues on this subject needed to be paid great attention to were discussed.

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