Size selection of Antarctic krill (Euphausia superba) in a commercial codend and trawl body

Herrmann, Bent; Krag, Ludvig Ahm; Krafft, Bjørn A.

doi:10.1016/j.fishres.2018.05.028

Cited by 70 publications

(57 citation statements)

References 19 publications

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“…To estimate 95% Efron CIs for each r Combined ( l ), we used the bootstrap sets obtained in Section 2.2 for each original design. Because these bootstrap sets were obtained independently, a new bootstrap set of results for r Combined ( l ) could be created using:

r_{Combined} {(l)}_{i} = r_{Herding} {(l)}_{i} \times r_{Body} {(l)}_{i} \times r_{Extension} {(l)}_{i} \times r_{Codend} {(l)}_{i} i \in [1 \dots 1000],

where i denotes the bootstrap repetition index (Herrmann, Krag, & Krafft, ). In Equation (2), the 1,000 bootstrap sets generated from the original data sets were multiplied to obtain the new bootstrap set for the combined configuration.…”

Section: Methodsmentioning

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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r_{Combined} {(l)}_{i} = r_{Herding} {(l)}_{i} \times r_{Body} {(l)}_{i} \times r_{Extension} {(l)}_{i} \times r_{Codend} {(l)}_{i} i \in [1 \dots 1000],

Section: Methodsmentioning

confidence: 99%

“…where i denotes the bootstrap repetition index (Herrmann, Krag, & Krafft, 2018). In Equation (2), the 1,000 bootstrap sets generated from the original data sets were multiplied to obtain the new bootstrap set for the combined configuration.…”

Section: Prediction Of Combined Selectivitymentioning

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

Self Cite

View full text Add to dashboard Cite

show abstract

“…The 95% CIs for ⌬r(l) were estimated based on the bootstrap population of results for the individual codends compared by the double bootstrap method described above. For details on this procedure, consult Herrmann et al (2018). Significant differences in size selection between codends was determined if the 95% CIs for ⌬r(l) had length classes that did not overlap 0.0.…”

Section: Selectivity Data Analysismentioning

confidence: 99%

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

Cheng

Winger

Bayse

et al. 2020

Can. J. Fish. Aquat. Sci.

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The size selectivity of four codends were compared in the Gulf of St. Lawrence, Canada redfish fishery, 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 is turned 90° to the direction of tow (T90). Results for the regulated codend showed that there was little size selection, catching greater than 97% of redfish over all of the length classes observed. Considering the fished population, the smallest T90 codend would catch 30% fewer redfish under the Minimum Landing Size (MLS) of 22 cm compared with the T0 codend, but would also lose 16% of catch above 22 cm. The T90 codend with 100 mm mesh opening had the same size selectivity as the smallest T90 codend. The 110 mm T90 codend would catch 50% less redfish below MLS but lose 40% of redfish above. Overall, results show that T90 codends improve size selectivity in which large proportions of undersized fish are successfully released.

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“…This was performed by calculating the ratio between the catch ratio curves obtained from the two catch ratio curves against the nylon net using the following equation: The 95% confidence intervals for CR(l,v) 0.60/0.55 were obtained based on the two bootstrap populations of results (1000 bootstrap repetitions in each) from each CR curve estimated for the 0.55 and 0.60 mm biodegradable gillnets against the nylon net. Since both bootstrap populations were obtained independently and the sampling to obtain those populations of results was performed randomly and independently, a new population of results with 1000 bootstrap iterations was created for CR(l,v) 0.60/0.55 following [36,37] Assessment of mechanical properties. Tensile testing were carried out on all the biodegradable and nylon PA gillnets used in the fishing experiments using a H10KT universal tensile testing machine (Tinius Olsen TMC, PA, USA) equipped with a load cell with 5000 Newton (N) rated force.…”

Section: Plos Onementioning

confidence: 99%

Effect of mechanical properties of monofilament twines on the catch efficiency of biodegradable gillnets

et al. 2020

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Gillnets made of the biodegradable resin polybutylene succinate co-adipate-co-terephthalate were tested under commercial fishing conditions to compare their fishing performance with that of conventional nylon polyamide (PA) gillnets. Both types of gillnets were made of 0.55 mm Ø monofilaments. However, since the biodegradable nets are weaker than nylon PA nets when using the same monofilament diameter, we also used biodegradable nets made of 0.60 mm Ø monofilament that had a similar tensile strength to the 0.55 mm Ø nylon PA nets. The relative catch efficiency of the different gillnet types was evaluated over the 2018 autumn fishing season for saithe and cod in northern Norway. For cod, both biodegradable gillnets (0.55 and 0.60 mm) had a significantly lower catch efficiency compared to the traditional nylon PA net (0.55 mm) with estimated catch efficiencies of 62.38% (CI: 50.55-74.04) and 54.96% (CI: 35.42-73.52) compared with the nylon PA net, respectively. Similarly for saithe, both biodegradable gillnets (0.55 and 0.60 mm) had a lower estimated catch efficiency compared to the traditional nylon PA net (0.55 mm) with estimated catch efficiencies of 83.40% (71.34-94.86) and 83.87% (66.36-104.92), compared with the nylon PA net, respectively. Tensile strength does not explain the differences in catch efficiency between the two gillnet types, since increasing the twine diameter of the biodegradable gillnets (to match the strength of nylon PA gillnets) did not yield similar catch efficiencies. However, the elasticity and stiffness of the materials may be responsible for the differences in catch efficiency between the nylon PA and biodegradable gillnets.

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Size selection of Antarctic krill (Euphausia superba) in a commercial codend and trawl body

Cited by 70 publications

References 19 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

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

Effect of mechanical properties of monofilament twines on the catch efficiency of biodegradable gillnets

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