The effect of grid spacing on size selectivity of shrimps in a pink shrimp trawl with a dual-grid size-sorting system

Abstract During the afternoon of 28 April 2015, a multicellular convective system swept southward through much of Jiangsu Province, China, over about 7 h, producing egg-sized hailstones on the ground. The hailstorm event is simulated using the Advanced Regional Prediction System (ARPS) at 1-km grid spacing. Different configurations of the Milbrandt–Yau microphysics scheme are used, predicting one, two, and three moments of the hydrometeor particle size distributions (PSDs). Simulated reflectivity and maximum estimated size of hail (MESH) derived from the simulations are verified against reflectivity observed by operational S-band Doppler radars and radar-derived MESH, respectively. Comparisons suggest that the general evolution of the hailstorm is better predicted by the three-moment scheme, and neighborhood-based MESH evaluation further confirms the advantage of the three-moment scheme in hail size prediction. Surface accumulated hail mass, number, and hail distribution characteristics within simulated storms are examined across sensitivity experiments. Results suggest that multimoment schemes produce more realistic hail distribution characteristics, with the three-moment scheme performing the best. Size sorting is found to play a significant role in determining hail distribution within the storms. Detailed microphysical budget analyses are conducted for each experiment, and results indicate that the differences in hail growth processes among the experiments can be mainly ascribed to the different treatments of the shape parameter within different microphysics schemes. Both the differences in size sorting and hail growth processes contribute to the simulated hail distribution differences within storms and at the surface.

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Reducing the catch of small shrimps in the Gulf of Maine pink shrimp fishery with a size-sorting grid device

ICES Journal of Marine Science ◽

10.1093/icesjms/fsm098 ◽

2007 ◽

Vol 64 (8) ◽

pp. 1551-1557 ◽

Cited By ~ 25

Author(s):

Pingguo He ◽

Vincent Balzano

Keyword(s):

Gulf Of Maine ◽

Marine Science ◽

Grid System ◽

Pink Shrimp ◽

Pandalus Borealis ◽

Shrimp Fishery ◽

Trawl Fishery ◽

Size Sorting ◽

Catch Rates

Abstract He, P., and Balzano, V. 2007. Reducing the catch of small shrimps in the Gulf of Maine pink shrimp fishery with a size-sorting grid device. – ICES Journal of Marine Science, 64: 1551–1557. Since implementation of the Nordmøre grid in the Gulf of Maine pink shrimp (Pandalus borealis) trawl fishery in the early 1990s, fish bycatch has been reduced drastically. However, the Nordmøre grid does not reduce the amount of small shrimps landed when the shrimps are on the fishing grounds. This paper reports on two designs of a new size-sorting grid system, one with a funnel and one without. The designs' main feature is the size-sorting grid's position, installed in front of the main Nordmøre grid. They were tested in the flume tank and at sea. Parallel tows involving two vessels and alternating tows using one vessel were made to compare the size-sorting grid system. Both size-sorting designs reduced the number of small shrimps in the catch significantly, by 38 and 45 kg−1 of catch, respectively. There was some reduction in shrimp catch rates, presumably from the release of small shrimps. There were no significant differences in the number or quantity of major bycatch species for the commercial grid and the two experimental grid designs. The designs were practical to operate and easy to install. Their application could reduce the catch of small shrimps in the pink shrimp fishery in the Gulf of Maine and in other areas.

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Size-Sorting and Measurement System of Safety Belt Pin Based on Machine Vision

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.741.709 ◽

2015 ◽

Vol 741 ◽

pp. 709-713 ◽

Cited By ~ 2

Author(s):

Li Gang Cao ◽

Ming Xiang ◽

Hao Feng ◽

Yong Yu Wang

Keyword(s):

Machine Vision ◽

Measurement Accuracy ◽

Image Process ◽

Control Logic ◽

Safety Belt ◽

Repeatability Error ◽

Improve Measurement ◽

Size Sorting ◽

Sorting System ◽

Telecentric Lens

To improve measurement accuracy of safety belt pin, the size-sorting system which mainly includes a machine vision subsystem and a driving subsystem, is researched. The machine vision subsystem includes a industry camera, a double telecentric lens and a backlight. Image process steps that have sub-pixel accuracy are presented. The driving subsystem is designed with Atmega128L MCU. The state machine is designed for safety pin control logic. The two sub systems communicate with RS232 serial port. The test shows that the system has a maximum accuracy error of 0.05mm, repeatability error of 0.013mm.

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Aspects of the biology of the Atlantic Midshipman, Porichthys porosissimus (Teleostei, Batrachoididae): an important by-catch species of shrimp trawling off southern Brazil

Revista Brasileira de Oceanografia ◽

10.1590/s1413-77392000000200004 ◽

2000 ◽

Vol 48 (2) ◽

pp. 131-140 ◽

Cited By ~ 6

Author(s):

Marcelo Vianna ◽

Acácio R. G. Tomas ◽

José R. Verani

Keyword(s):

Growth Parameters ◽

Northern Coast ◽

Pink Shrimp ◽

Stock Management ◽

Spawning Period ◽

Management Measures ◽

Shrimp Trawl ◽

Trawl Fishing ◽

By Catch ◽

The Impact

Trawl fishing for pink shrimp (Farfantepenaeus brasiliensis and F. paulensis) catches large quantities of by-catch fish, discarded due to their having no commercial va)ue. As these species have rarely been studied, the impact of fisheries on these populations is not known. This contribution studies the biology of a species of no commercial value, the Atlantic midshipman Porichthys porosissimus. The last haul /Tom a commercial trawler, operating on the northern coast of São Paulo State and the southern coast of Rio de Janeiro State, was preserved (/Tom being discarded) and identified at the species leveI. It was observed that this fishery affects the juvenile population which is intluenced by the seasonal variation of the water masses. Growth parameters were estimated: L∞ = 37.0 cm, K = 0.285 year-1. Instantaneous mortality coefficients were estimated: 2=2.14, M=0.63, F= 1.51, S= 11.8 and E=0.71. Considering the intensive activity of the shrimp trawl tleet operating in this area, the deleterious action of trawling is considered as of high impact. The stock management measures applied for pink shrimp are without effect regarding P. porosissimus. which has its spawning period before the closed season and its recruitment peak after it. The results show overfishing and the need to apply measures to reduce trawling action, such as adequate policies, introduction of selectivity devices and the creation of exclusion zones for trawl fishing.

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