Shanghai Collaborative Innovation Center for Oceanic Fisheries

Shanghai, China

Shanghai Collaborative Innovation Center for Oceanic Fisheries

Shanghai, China
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Tang H.,Shanghai Ocean University | Hu F.,Tokyo University of Marine Science and Technology | Xu L.,Shanghai Ocean University | Xu L.,National Engineering Research Center for Oceanic Fisheries | And 6 more authors.
Journal of Ocean University of China | Year: 2017

Knotless polyethylene (PE) netting has been widely used in aquaculture cages and fishing gears, especially in Japan. In this study, the hydrodynamic coefficient of six knotless PE netting panels with different solidity ratios were assessed in a flume tank under various attack angles of netting from 0° (parallel to flow) to 90° (perpendicular to flow) and current speeds from 40 cm s−1 to 130 cm s−1. It was found that the drag coefficient was related to Reynolds number, solidity ratio and attack angle of netting. The solidity ratio was positively related with drag coefficient for netting panel perpendicular to flow, whereas when setting the netting panel parallel to the flow the opposite result was obtained. For netting panels placed at an angle to the flow, the lift coefficient reached the maximum at an attack angle of 50° and then decreased as the attack angle further increased. The solidity ratio had a dual influence on drag coefficient of inclined netting panels. Compared to result in the literature, the normal drag coefficient of knotless PE netting measured in this study is larger than that of nylon netting or Dyneema netting. © 2017, Science Press, Ocean University of China and Springer-Verlag GmbH Germany.


Tang H.,Shanghai Ocean University | Xu L.,Shanghai Ocean University | Xu L.,National Engineering Research Center for Oceanic Fisheries | Xu L.,Shanghai Collaborative Innovation Center for Oceanic Fisheries | And 6 more authors.
Turkish Journal of Fisheries and Aquatic Sciences | Year: 2017

Gear performance evaluation for tuna purse seine using both full-scale sea trials and model testing was designed in the study. A model tuna purse seine of 1:20 scale was constructed and tested in Lake Qiandao, China in 2013; and the field observations of its full-scale net in operation was conducted on board a typical Chinese tuna vessels during 2006; the physical model testing data were then assessed to determine the model’s ability to predict main performance parameters of full-scale net at sea. A generalized linear model (GLM) was employed to standardize and compare sinking performance between the model net and its prototype. It was found that increase in leadline weight or setting speed of net was conductive to improved sinking performance. The leadline weight was the most important controllable factor affecting sinking performance of the purse seine, the sinking speed in wing end position was higher in comparison to that in other position of model net. Though there is likely no fully ideal model net which can be used to accurately predict full-scale at-sea performance, our sea trials and physical model testing showed consistent results, indicating our model testing method can be used as an important complement method to successfully evaluate the purse seine performance at sea. © Published by Central Fisheries Research Institute (CFRI) Trabzon, Turkey in cooperation with Japan International Cooperation Agency (JICA), Japan.


Zhou C.,Shanghai Ocean University | Xu L.,Shanghai Ocean University | Xu L.,National Engineering Research Center for Oceanic Fisheries | Xu L.,Shanghai Collaborative Innovation Center for Oceanic Fisheries | And 2 more authors.
Fisheries Research | Year: 2015

Vessel position and shooting direction relative to current direction can potentially affect the movement and spatial geometry of purse seine during fishing operations. This study developed an image measurement algorithm to obtain kinetic transformation of a model net when setting in different patterns (shooting with current, front set in shorthand: shooting against current, back set; and shooting lateral to current, cross set) in a specialized purse seine test tank. The results showed some differences in the pattern of deformation in the leadline and floatline. Front set produced the greatest encircled volume by minimizing the area contraction with the open area for floatline in real operation of 0.259km2 in cross set, 0.266km2 in front set, and 0.257km2 in back set, respectively. Different sinking curves were observed in the vertical configuration of middle part of leadline among shooting patterns. Back set is considered as the optimal strategy of setting the net judged from the sinking behavior, as it provides the greatest sinking depth in the middle part of the net. The seiner moved the greatest distance downstream in back set, while the greatest drifting distance inward the circle occurred in front set where it is likely to lead to the seiner drifting over the net. Purse line tension increased continuously until the conclusion of pursing and the bunt was subjected to greater tension force than that at the wing end. © 2015 Elsevier B.V.


Zhou C.,Shanghai Ocean University | Xu L.,Shanghai Ocean University | Xu L.,National Engineering Research Center for Oceanic Fisheries | Xu L.,Shanghai Collaborative Innovation Center for Oceanic Fisheries | And 4 more authors.
Fisheries Science | Year: 2015

One of the greatest concerns for a successful catch in tuna fishing operations is the diving behavior of the purse seine. To analyze the integrated effect of fishing methods and sea currents on purse seine sinking depth, a multiple regression model was used. This improved model shows current speeds, shooting duration, the included angle between a two-layer current, and net mouth orientation relative to current direction (shooting angle) have an influence on maximum sinking depth. The current in the mid-layer is considered to significantly resist the seine’s vertical dive by a quadratic relation, but an increased shooting duration and shooting angle can be enhance the sinking. An obvious difference in terms of sinking depth is found between free-swimming school fishing and floating objects fishing, two common methods in tuna purse seine fisheries. It has been suggested that seine sinking dynamics respond to gear manipulation and, therefore, the model provides useful guidance in implementing net casting for an effective capture. © 2015, Japanese Society of Fisheries Science.


Zhou C.,Shanghai Ocean University | Xu L.,Shanghai Ocean University | Xu L.,National Engineering Research Center for Oceanic Fisheries | Xu L.,Shanghai Collaborative Innovation Center for Oceanic Fisheries | And 2 more authors.
Ocean Engineering | Year: 2015

Nylon fiber is the dominant material for net panels in purse seine tackle. Nets of a knotless nylon weave called "Ultra Cross" benefit from higher strength and attrition-resistant properties over conventional twisted netting. This study reports the hydrodynamic characteristics of knotless nylon netting with various solidity ratio in their normal, parallel, and angle of incline to free stream. Normal drag coefficient is considered to be dependent on the cooperative domination of Reynolds number (Re) and solidity ratio. Net solidity has a positive effect on the normal coefficient, while it is contrary in the dependence of the drag coefficient of net panel parallel to flow on the solidity. A dual effect of solidity on drag coefficient for inclined nets was observed, which is described as a positive correlation in upper attack angle and a negative correlation in lower angle of attack. The drag coefficients at different angles of attack can be expressed by incorporating both normal coefficient and coefficient in parallel orientation. © 2015 Elsevier Ltd.


Zhou C.,Shanghai Ocean University | Xu L.,Shanghai Ocean University | Xu L.,National Engineering Research Center for Oceanic Fisheries | Xu L.,Shanghai Collaborative Innovation Center for Oceanic Fisheries | And 6 more authors.
Journal of Ocean University of China | Year: 2014

This study applies the mass-spring system to model the dynamic behavior of a submerged net panel similar to the shooting process in actual purse seine fishing operation. Modeling indicates that there is insufficient stretching with the net panel under the floatline in the prophase of the shooting process. Sinkers at different locations along the leadline descend successively after submergence, and the sinking speed decreases gradually with elapsed time until attainment of a stable state. Designs with different current speeds and sinker weights are executed to determine the dimensional shape and sinking characteristics of the net. The net rigged with greater sinker weight gains significantly greater sinking depth without water flow. Compared with the vertical spread of the net wall in static water, the middle part of the netting presents a larger displacement along the direction of current under flow condition. It follows that considerable deformation of the netting occurs with higher current speed as the sinkers affected by hydrodynamic force drift in the direction of current. The numerical model is verified by a comparison between simulated results and sea measurements. The calculated values generally coincide with the observed ones, with the former being slightly higher than the latter. This study provides an implicit algorithm which saves computational loads for enormous systems such as purse seines, and ensures the accuracy and stability of numerical solutions in a repetitious iteration process. © 2015, Science Press, Ocean University of China and Springer-Verlag Berlin Heidelberg.

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