Shanghai Collaborative Innovation Center for Oceanic Fisheries

Shanghai, China

Shanghai Collaborative Innovation Center for Oceanic Fisheries

Shanghai, China

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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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