Out with the old and in with the new: T90 codends improve size selectivity in the Canadian redfish (<i>Sebastes mentella</i>) trawl fishery

In many trawl fisheries, codend size selectivity is supplemented by adding selection devices to the gear. In the Barents Sea gadoid fishery, combining diamond mesh codends with sorting grids is compulsory. However, the use of grids increases the costs and complexity of the gear, causing discontent among fishermen and prompting researchers to seek alternative solutions. Lastridge ropes are ropes attached to the selvedges of the codend. In this study, we tested the effect of shortening the lastridge ropes of two diamond mesh codends with different mesh sizes on the size selectivity of cod (Gadus morhua), haddock (Melanogramus aeglefinnus), and redfish (Sebastes spp.). Shortening the lastridge ropes by 15% increased the mesh opening during the fishing process, which significantly improved the size-selective properties of the codends. Further, the L50 values were always higher for the codends in the short lastridge configuration. Therefore, codends with shortened lastridge ropes may be a simpler alternative to sorting grids in this fishery, and they may be applicable to many other fisheries in which additional selection devices are used.

mentioning

confidence: 99%

Potential for codends with shortened lastridge ropes to replace mandated selection devices in demersal trawl fisheries

Sistiaga

Brinkhof²,

Herrmann³

et al. 2022

“…The 110 mm T90 codend would catch 50% less redfish below MLS but lose 40% of redfish above MLS. Overall, the results showed that T90 codends improve size selectivity in which large proportions of undersized fish can be successfully released (Cheng et al 2020).…”

Section: Fish Capturementioning

confidence: 88%

“…They compared the size selectivity of four codends in Unit 1, including the regulated diamond mesh codend with a mesh opening of 90 mm (T0) and three experimental codends of different mesh openings (90, 100, 110 mm) in which the netting was turned 90 • to the direction of tow (referred to as T90). Results for the regulated codend showed that there was little size selection, catching greater than 97% of redfish over all the length classes observed (Cheng et al 2020). Considering the fished population, the smallest T90 codend would catch 30% fewer redfish under the minimum landing size (MLS) of For personal use only.…”

Section: Fish Capturementioning

confidence: 97%

“…More recently, Cheng et al (2020) investigated the effect of mesh orientation on the size selectivity of redfish (S. mentella). They compared the size selectivity of four codends in Unit 1, including the regulated diamond mesh codend with a mesh opening of 90 mm (T0) and three experimental codends of different mesh openings (90, 100, 110 mm) in which the netting was turned 90 • to the direction of tow (referred to as T90).…”

Section: Fish Capturementioning

confidence: 99%

See 1 more Smart Citation

Northwest Atlantic redfish science priorities for managing an enigmatic species complex

Cadigan

Duplisea²,

Senay

et al. 2022

Redfish (Sebastes spp.) in the Northwest Atlantic (NWA) extend from Baffin Island in the north to the Gulf of Maine in the south. The two most abundant species are S. mentella and S. fasciatus, which are morphometrically similar and difficult to visually distinguish. Redfish are long-lived, slow-growing, late-maturing, tend to produce large year classes episodically, and have complex population structure. Intraspecific genetic groups are abundant in the NWA. They are often semi-pelagic and patchily distributed, which makes them difficult to survey. These are all characteristics that cause difficulties for stock assessment and for sustainable fisheries management. This was the focus of The Ocean Frontier Institute Northwest Atlantic Redfish Symposium in 2018. In this paper we synthesize the information known about NWA redfish. To improve the scientific basis for sustainable harvest strategies, key research recommendations involve: 1) improved biological sampling including species and ecotype; 2) develop integrated stock assessment models; 3) develop harvest strategies with management reference points that are appropriate for redfish; 4) improve fishing technology and practices to avoid capture of small non-marketable redfish and other species.

“…This study sought to alleviate the consequences that arise in deep-water shrimp fisheries as a result of insufficient codend mesh openings (Cheng et al 2020). In order to increase codend mesh openness and thus enabling an increase in escape of deep-water shrimp below the MS and juvenile fish, two approaches were taken.…”

mentioning

confidence: 99%

Bycatch reduction in the deep-water shrimp (Pandalus borealis) trawl fishery by increasing codend mesh openness

Jacques¹,

Pettersen²,

Cerbule³

et al. 2022

In most trawl fisheries, drag forces tend to close the meshes in large areas of diamond mesh codends, negatively affecting their selective potential. In the Barents Sea deep-water shrimp (Pandalus borealis) trawl fishery, selectivity is based on a sorting grid followed by a diamond mesh codend. However, the retention of juvenile fish as well as undersized shrimp is still a problem. In this study, we estimated the effect of applying different codend modifications, each aimed at affecting codend mesh openness and thereby selectivity. Changing from a 4-panel to a 2-panel construction of the codend did not affect size selectivity. Shortening the lastridge ropes of a 4-panel codend by 20% resulted in minor reductions for juvenile fish bycatch, but a 45% reduction of undersized shrimp was observed. Target-size catches of shrimp were nearly unaffected. When the codend mesh circumference was reduced while simultaneously shortening the lastridge ropes, the effect on catch efficiency for shrimp or juvenile fish bycatch was marginal compared to a 4-panel codend design with shortened lastridge ropes.