A simplified model of the interaction of the trawl warps, the otterboards and netting drag

Prat, Josep; Antonijuan, J.; Folch, Arnau; Sala, Antonello; Lucchetti, Alessandro; Sardà, Francisco; Mànuel, A.

doi:10.1016/j.fishres.2008.07.007

Cited by 39 publications

(22 citation statements)

References 17 publications

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“…Interaction effects were evaluated between variables for each regression, either in physical modeling or in dynamic simulation, and effects found were not considered significant (p < 0.05). In specific terms, the total drag (TD) and net drag (ND) can be explained by the speed (S) and the wing-end spread (WS), as reported by Fiorentini et al (2004) and Prat et al (2008) who relates net drag with the squared speed:…”

Section: Discussionmentioning

confidence: 99%

“…One can clearly examine the effects of alterations to the design and rigging, effect of towing speed on geometry and orientation, and measuring forces acting on the gear and to measure motions of fishing gear. Although, computational modeling is a valuable complementary tool to assess behavior of bottom trawl fishing gears (Prat et al, 2008), and it can estimate net shape configurations and loads (Niedzwiedz and Hopp, 1998), design defects are clearly visible in flume tank and do not require more questioning, while viewing the results of the simulation is much more complex. This was demonstrated in the evaluation stages of the model in the flume tank, where it was possible to observe deficiencies in the estimation of riblines lengths that were corrected.…”

Section: Discussionmentioning

confidence: 99%

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Comparison between dynamic simulation and physical model testing of new trawl design for Chilean crustacean fisheries

2009

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Comparison between dynamic simulation and physical model testing of new trawl design for Chilean crustacean fisheries

2009

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“…Gear performance (i.e., door spread, horizontal and vertical net openings) was measured on all hauls using the SCANBAS SGM-15 system (SCANMAR, Norway). A laptop, with customized software, automatically controlled data acquisition and provided real-time information about the correct functioning of the system (Prat et al 2008;Sala et al 2009). The main goal of these measurements was to obtain detailed real time data on gear performance for each haul, in order to determine possible influences of the TED on net behaviour and to calculate vessel speed and tow duration.…”

Section: Sea Trials and Gear Behaviour Performancementioning

confidence: 99%

Effects of Turtle Excluder Devices on bycatch and discard reduction in the demersal fisheries of Mediterranean Sea

Sala

Lucchetti

Affronte

2011

Aquat. Living Resour.

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-The Central Mediterranean provides important neritic habitats for loggerhead turtles (Caretta caretta), but Mediterranean bottom trawlers catch an estimated 30 000 turtles a year, with 25% mortality. Mortality by trawling is mainly due to enforced apnoea during towing activity. In order to reduce the submergence time and consequent turtle mortality, a specific technical modification was developed in the early 1980s: the Turtle Excluder Device (TED). In this paper, we field-tested a typical Supershooter TED and three new types of low-cost TED, built with different designs and materials, incorporating aspects of US and Australian TEDs, as well as design features to improve handling and catch rates. The performance of the TEDs was investigated under commercial fishing conditions in diverse trawling grounds in the Adriatic Sea (Mediterranean). All TEDs were easy to operate and did not require changes to normal fishing operations. Due to lack of entry of turtles it was not possible to evaluate the ability of the different TEDs to release turtles, but one large loggerhead turtle (C. caretta) was captured during the experimental tows and was successfully excluded by the Supershooter. The TEDs reduced anthropogenic debris and, consequently, sorting operations on board. Among the four TEDs tested, both the semi-rigid TED and the Supershooter performed in accordance with the design objectives: total discards were reduced but total commercial catches were not significantly reduced. With the Supershooter, all European hake (Merluccius merluccius) individuals equal to or above 16 cm were found in the codend and 10-15% of those between 5.0 and 15.5 cm were released. In general, the total discard rate of the TED-equipped nets was reduced to around 20-60%. Since the Council Regulation (EC) No. 1967/2006 called for a discard reduction policy in waters under the jurisdiction of the European Union, TEDs may have some broader value in this context.

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“…There also exist studies that compare flume tank results with full-scale sea trial data for both isolated nets and full gear [50,13,18]. In addition, a number of numerical models to simulate net dynamics have been developed [3,23,27,49,34,44,20], and also some models of complete gears, including a crude [19] or somewhat fair [14,33] description of trawl door behaviour, have been devised. A careful literature search shows that the first and only full trawl gear simulation embodying thorough modelling of the otter boards was undertaken by [35].…”

Section: Introductionmentioning

confidence: 99%

Testing otter board hydrodynamic performances in wind tunnel facilities

et al. 2015

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The feasibility and potential advantages of wind tunnel testing of otter board designs is assessed. Traditional flume tank tests incur high operational costs and present some limitations in terms of flexibility and accuracy. Modern flume tanks, despite more flexible and accurate, are still expensive to operate or hire. Wind tunnel facilities are widespread, with a potential for low budget tests, and allow for an accurate control of velocity, angle of attack and sideslip as well as precise measurement of forces and moments in all three axes. A complete description of otter board hydrodynamics is paramount to optimising design and rigging and for the design of active control strategies that allow for stable trawling at a target speed and depth. We describe in detail the methodology of wind tunnel tests applied to general otter board designs, exemplify it with a commercial pelagic otter board and provide a comparison with existing flume tank results for the same design.

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A simplified model of the interaction of the trawl warps, the otterboards and netting drag

Cited by 39 publications

References 17 publications

Comparison between dynamic simulation and physical model testing of new trawl design for Chilean crustacean fisheries

Comparison between dynamic simulation and physical model testing of new trawl design for Chilean crustacean fisheries

Effects of Turtle Excluder Devices on bycatch and discard reduction in the demersal fisheries of Mediterranean Sea

Testing otter board hydrodynamic performances in wind tunnel facilities

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