A meta-analysis of vertical stratification in demersal trawl gears

Fryer, R. J.; Summerbell, K.; O’Neill, Fiona

doi:10.1139/cjfas-2016-0391

Cited by 16 publications

(14 citation statements)

References 53 publications

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“…In contrast, even though the BRD combinations identified here would reduce commercial catches of some species (e.g. haddock), they are likely to allow the retention of others, such as monkfish ( Lophius piscatorius ) and flatfish species, less affected by these types of BRDs (Fryer et al, ; Krag et al, ; Melli, Karlsen, et al, ).…”

Section: Application To a Case‐study Fisherymentioning

confidence: 89%

“…http://www.discardless.eu/selectivity_manual; http://www.seafish.org/geardb/; https://tool.gearingup.eu/; O'Neill et al, ; O'Neill & Mutch, ). Moreover, results from different studies have been combined through meta‐analyses to extrapolate common patterns useful in designing future gear modifications (Fryer, O'Neill, & Edridge, ; Fryer, Summerbell, & O'Neill, ; ICES, ; Madsen, ). Ideally, both scientists and fishermen could use this information to choose the most appropriate gear design with respect to their specific catch goals (O'Neill et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Predicting optimal combinations of by‐catch reduction devices in trawl gears: A meta‐analytical approach

Melli¹,

Herrmann

Karlsen³

et al. 2019

Fish and Fisheries

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Global efforts to reduce unwanted catches have led to the development of a vast array of by‐catch reduction devices (BRDs), in particular for mixed trawl fisheries. Some of these BRDs could likely benefit from being combined. However, the number of possible combinations would be prohibitive to be tested experimentally. Therefore, in this study we propose a meta‐analytical approach that combines the data available on BRDs tested independently in a fishery and predict the theoretical selectivity of all possible combinations of those devices. This allows to identify promising BRD combinations, worth experimental investigation and flexible trawl configurations, where the selectivity can be substantially modified by adding or removing one BRD, thus aiding fishermen in adapting to high variability in catch composition and quota availability. To illustrate the approach, we used BRDs developed for the well‐studied Nephrops (Nephrops norvegicus, Nephropidae) directed mixed trawl fishery in the Skagerrak and Kattegat seas. We predicted the selectivity of 100 BRD combinations for Nephrops, cod (Gadus morhua, Gadidae) and haddock (Melanogrammus aeglefinus, Gadidae), compared them in terms of absolute selectivity and performance under realistic catch scenarios, from both single‐ and multispecies perspectives, and identified 15 BRD combinations that could be worth future experimental investigation. The meta‐analytical approach makes best use of existing knowledge and leads to new insights about the potential for improvement and flexibility in trawl selectivity. This could benefit a variety of mixed trawl fisheries and help developing a new generation of more flexible gears, with multiple BRDs integrated in their structure.

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Section: Application To a Case‐study Fisherymentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Predicting optimal combinations of by‐catch reduction devices in trawl gears: A meta‐analytical approach

Melli¹,

Herrmann

Karlsen³

et al. 2019

Fish and Fisheries

View full text Add to dashboard Cite

show abstract

“…Madsen (2007) carried out such an analysis for cod (Gadus morhua), Perez Comas and Pikitch (1994) for a range of gadoid species and ICES (2007) for Norway lobster (Nephrops norvegicus). Another study estimated the proportion of several species that enter a trawl above or below a given height, which will be very useful in designing species selective gears such as low headline or raised footrope trawls (Fryer et al 2017) (Fig. 14.3).…”

Section: Making Best Use Of Existing Informationmentioning

confidence: 99%

“…14.3 The proportion of fish that will enter a trawl gear above a given height. The vertical red lines indicate the proportion of each species that would enter above a height of 1 m (Fryer et al 2017). The trawl gears on the right illustrate how net makers can make use of this type of information to influence the species profile entering a gear by altering the height and position of the headline.…”

Section: Making Best Use Of Existing Informationmentioning

confidence: 99%

Discard Avoidance by Improving Fishing Gear Selectivity: Helping the Fishing Industry Help Itself

O’Neill

Feekings

Fryer

et al. 2018

The European Landing Obligation

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To address the challenges of the Landing Obligation, fishers need to be able to adjust the selective performance of each fishing operation in response to what they observe on the fishing grounds and to what they bring on board. This will include strategies on where and when to fish but also on how to fish, which we examine here. In particular, we focus on ways to encourage and support fishers to design, develop and test selective gears that will avoid unwanted catches in the first place. To this end, we highlight the necessity to increase awareness of existing solutions, the importance of understanding the capture process and how fish react to fishing gears, and the need to evaluate the economic implications of new gears. We examine the success of science-industry collaborations and emphasise the benefits of a flexible regulatory environment. Looking ahead, the fishing industry needs to keep up-to-date with new technologies that can be used to observe the interaction of fish and their gears and with new approaches to modifying selectivity.

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“…Making changes to the selectivity of fishing gear is an approach often investigated to reduce discards but avoiding unwanted catches through changes in spatio-temporal fishing strategies is another important strategy which has, however, received less attention. Sea trials of selective gear have been performed throughout Europe with additional meta-analysis (Fryer et al 2016(Fryer et al , 2017 and resources, which collate and summarise how different modifications may influence the escape of different species. These resources aim to make fishermen, net makers and fisheries managers aware of the possible modifications that can be made to fishing gears, and so develop gears with a selective performance suitable for their particular fishery (GearingUp, 2017;O'Neill and Mutch, 2017;SeaFish, 2018).…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of discards in mixed fisheries: species trade-offs, potential spatial avoidance and national contrasts

Robert

Calderwood

Radford

et al. 2019

Rev Fish Biol Fisheries

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Since 2015, the European Union gradually implemented the landing obligation (LO). This prohibits at-sea discarding of species under total allowable catch management. Spatiotemporal avoidance strategies and increasing fishing gear selectivity are two complementary levers that could help fishers in reducing the amount of discards. The objective of this paper is to analyse discarding practices of demersal mixed fisheries in the central part of the Celtic Sea to inform on potential spatial avoidance strategies of unwanted catches in a multi-species context. This study provides the first international and fine scale discard maps based on combined observer at-sea data from Ireland, France and the UK, the main countries fishing in the area. Using a suite of multivariate analyses, we identified areas with similar discard profiles, accounting for the multi-species nature of the fisheries. The maps were also derived separately for the three countries to examine national versus general patterns. Strong spatial segregation in effort between the countries, combined with nationally distinct quotas constraints, fisheries targets and market preferences, resulted in limited differences in the species composition of discards, but considerable differences in spatial discard patterns between countries. In theory, the maps based on discards below and above the minimum conservation reference size could inform fishers on areas to avoid but in practice, the spatial ubiquity of some species involved and strong technical interactions between fishing gears limit the possibility of avoiding discards. Some species trade-offs could be identified that might help to minimize adverse impacts of the implementation of the LO.

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A meta-analysis of vertical stratification in demersal trawl gears

Cited by 16 publications

References 53 publications

Predicting optimal combinations of by‐catch reduction devices in trawl gears: A meta‐analytical approach

Predicting optimal combinations of by‐catch reduction devices in trawl gears: A meta‐analytical approach

Discard Avoidance by Improving Fishing Gear Selectivity: Helping the Fishing Industry Help Itself

Spatial distribution of discards in mixed fisheries: species trade-offs, potential spatial avoidance and national contrasts

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