Catch Rates Of Shrimp Research Articles

Shorter trawls improve size selection of northern shrimp

Discards of small northern shrimp (Pandalus borealis) are a problem in the Skagerrak northern shrimp trawl fishery. To reduce catches of small shrimp, we studied the effect of trawl belly length on size selectivity in November 2017 and June 2018 onboard 15 and 27 m double-rigged shrimp trawlers. The selectivity of the vessels’ standard trawl was compared with a trawl differing only in the belly length, being 37% shorter. The trawls had 40 mm bottom panels and cod ends of 35 mm mesh sizes. Eleven and 14 hauls were made, respectively, in 2017 aboard the 15 m vessel and in 2018 aboard the 27 m vessel. The trawls fished shrimp above 19 mm carapace length equally, while catch rates of shrimp below 15.5–16 mm carapace length in the shorter trawl were more than halved. The results were consistent between the two vessels. In short, modifying trawl length is a simple design modification that can reduce catches of small shrimp. Bycatch of Norway pout (Trisopterus esmarkii) was slightly reduced in the shorter trawl, unrelated to fish length.

Improving Size Selectivity of Shrimp Trawls in the Gulf of Maine with a Modified Dual‐Grid Size‐Sorting System

AbstractFinfish bycatch has been drastically reduced since the Nordmøre grid became mandatory in 1992 in the Gulf of Maine trawl fishery for northern shrimp Pandalus borealis. However, the Nordmøre grid does not improve northern shrimp size selection, catching large numbers of small shrimp when they are mixed with large mature shrimp. To reduce the catch of small northern shrimp, a new dual‐grid shrimp size‐sorting system was developed and tested in a flume tank and at sea to evaluate its potential for reducing catch of juvenile and male shrimp in the Gulf of Maine northern shrimp fishery and to optimize rigging. These tests used a trouser trawl system consisting of one trawl leading to two separate cod ends, which compared a cod end with a dual‐grid size‐sorting system with another identical cod end without a size‐sorting grid. The size‐sorting grid had 11‐mm bar spacing. The dual‐grid size‐sorting system significantly reduced the number of small northern shrimp with a carapace length of 22 mm or less and slightly increased catch of large shrimp with a carapace length of 23 mm or larger, when compared with the Nordmøre grid without a size‐sorting grid. There was a slight reduction of northern shrimp catch rates due to the release of smaller shrimp but with no significant differences in the number or quantity of major bycatch species between the regular grid and the size‐sorting grid. The new dual‐grid system was practical to operate and a significant improvement over an earlier version of the size‐sorting grid in design, rigging, and handling. The application may reduce small shrimp in other northern shrimp fisheries and other shrimp and prawn fisheries with suitable modification to the design.Received July 15, 2011; accepted August 2, 2012

Catch rates as indicators of ecosystem health and exploitation status in the shrimp fishery in the South China sea

Based on catch and effort data analyses covering the period 1996–2002, time series of catch rates in the trawl fisheries in the South China Sea along the coasts of Bac Lieu and Ca Mau in South East Vietnam were estimated. The indicators include catch rates for total shrimp catch, five major shrimp catch groups and 15 commercial shrimp groups estimated as quarterly averages for trawlers divided into five size groups. The analyses indicated that despite a reduction in catch rates, shrimp is still the principal resource for the trawl fleets in South Vietnam. Seasonality in the shrimp catch rates that might reflect seasonality in shrimp recruitment was found, making this resource potentially suitable for a fishery management system based on closed seasons. Further, the data indicate that the major part of the catches are comprised of low value species belonging to the genera Parapenaeopsis; whereas the most valuable species, i.e. the Penaeus and Metapenaeus catch groups have been significantly depleted during the period investigated. Based on the experiences from the present analysis, recommendations are presented with regard to adjustments of the enumerator data collection programme to fulfil the requirement of a dynamic fishery management system.

The rise and fall of electrical beam trawling for shrimp in the East China Sea: technology, fishery, and conservation implications

Abstract Yu, C., Chen, Z., Chen, L., and He, P. 2007. The rise and fall of electrical shrimp beam trawling in the East China Sea: technology, fishery, and conservation implications. – ICES Journal of Marine Science, 64: 1592–1597. Since the 1980s, shrimp beam trawling has flourished in inshore waters of the East China Sea (ECS) off Zhejiang Province. By 2000, there were more than 10 000 beam trawlers operating in the area. The fishery targets several species of shrimp, including Parapenaeopsis hardwickii, Solenocera crassicornis, Parapenaeus fissuroides, and Trachypenaeus curvirostris. In the early 1990s, electrical beam trawls using pulse generators, powered either from the vessel or from underwater battery packs, became popular in the fishery. As a result of this new technology, the catch rates of shrimp, especially the burrowing shrimp species, increased. At its peak usage, there were more than 3000 vessels using electrical beam trawls in Zhejiang Province and another 500 or more in the adjacent provinces of Jiangsu and Fujian. This technology was also widespread along the Chinese coast, but a lack of regulation resulted in the misuse of electrical pulse parameters that caused damage to juvenile shrimps and other benthic species. In 2001, this fishing method was banned from the waters off Zhejiang Province, and subsequently in other parts of the ECS. This paper reviews the research on electrical beam trawls, the fishery, and fishery-management issues associated with this new technology.

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

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.

Variabilidad circadiana de la tasa de captura y la estructura de tallas en camarones e ictiofauna acompañante en la pesquería de arrastre del Mar Caribe de Colombia

Diel-associated changes of catch rates and size-structure of shrimp (Farfantepenaeus notialis and F. bra- siliensis), incidental catches, discards and the twelve most caught fish species of each of the two shrimp trawling fishing zones (northern and southern) of the Colombian Caribbean Sea were examined. Data were obtained by on board observers between July and September 2004. Although individuals shrimps in daytime catches were larger in size, shrimp catch rates were significantly higher at nightime, wich confirm the nocturnal activity of the shimps (Penaeidae).Higher catch rates and few large individuals of predator fish species were observed during daytime. The total catch (mostly discarded, small-sized species) was significantly higher at night. Observed circadian variability in catch rates and size composition suggests diel rhythms in activity of examined species and indicates that the abundance indexes can be biased if sampling is not randomised by time of day. High amounts of discarded small sized individuals reveal a heavy fishing pressure in the region and indicate the urgent need for management measures to mitigate impacts of trawling.

Characterisation and standardisation of a red shrimp <i>Aristeus antennatus</i>, (Risso, 1816) fishery off the Alicante gulf (SE Spain)

SUMMARY: The red shrimp (Aristeus antennatus) is a target species of a deep trawl fishery in the Gulf of Alicante. This paper describes the fishery by following the activity of this trawl fleet between 1992 and 1999. Principal Components Analysis (PCA) of specific catch compositions identified five main components that explained 92% of the variability, and the catches were grouped into three main species: red shrimp, hake and blue whiting. Hierarchical Clustering Grouping of the percentage species catch composition allowed the fleet to be considered as two main groups, according to monthly landings and by differentiating the origin of the catches (slope or shelf). The species composition of the catch and the red shrimp catch rates (CPUE) differed between the two fleet groups. The application of Generalised Linear Modelling (GLM) to the CPUE series gave consistent indices of abundance. The fleet group, year and season had significant effects on shrimp catch rates, with the fleet group being the most important, and these models explained up to 62% of the total deviance. The abundance indices showed little variation from 1992, although 1994 had the highest value and 1997-1998 the lowest. Comparison with survey indices showed similar trends, while mean uncorrected CPUE differed. Monthly variations of shrimp indices showed a lower abundance in summer, which was attributed to the reproductive patterns of the species. As a result, the use of some fleet grouping techniques is recommended before standardising CPUEs to obtain trends or to calibrate assessment in a fishery.

Results of an Experimental Shrimp Fishery in Chaleur Bay, Southern Gulf of St. Lawrence

Abstract Five surveys of coastal shrimp abundance and distribution were conducted aboard a commercial shrimp trawler between 25 Aug and 4 Nov 1997 to evaluate the potential for a commercial shrimp fishery in Chaleur Bay, southern Gulf of St. Lawrence. The net was equipped with a fish exclusion grate (25-mm bar spacing) to reduce fish bycatch. The initial target species was sevenspine bay shrimp Crangon Sepemspinosa, but very few were captured in the depths fished (20–82 m). The principal shrimp species captured were Aesop shrimp Pandalus montagui and Arctic argid Argis dentata. The catch rates of shrimp were too low to support a commercial shrimp fishery in Chaleur Bay. Average catch rates for Aesop shrimp ranged between 0.5 and 3.2 kg/h (whole animals, wet weight), and catch rates for Arctic argid ranged between 0.5 and 9.3 kg/h. Bycatch of fish was low (usually <10 kg/h) from late Aug to Oct but were excessive during early Nov when an average of 102 kg/h of Atlantic herring Clupea harengus and rainbow s...