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Size selection of Antarctic krill (Euphausia superba) in trawls.

Krag LA, Herrmann B, Iversen SA, Engås A, Nordrum S, Krafft BA - PLoS ONE (2014)

Bottom Line: However, our results indicated that size selectivity of krill is a well-defined process in which individuals encounter meshes at an optimal orientation for escapement.The simulation-based results were supported by data from experimental trawl hauls and underwater video images of the mesh geometry during fishing.The methods developed and results described are important tools for selecting optimal trawl designs for krill fishing.

View Article: PubMed Central - PubMed

Affiliation: DTU Aqua, Technical University of Denmark, Hirtshals, Denmark.

ABSTRACT
Trawlers involved in the Antarctic krill (Euphausia superba) fishery use different trawl designs, and very little is known about the size selectivity of the various gears. Size selectivity quantifies a given trawl's ability to catch different sizes of a harvested entity, and this information is crucial for the management of a sustainable fishery. We established a morphological description of krill and used it in a mathematical model (FISHSELECT) to predict the selective potential of diamond meshes measuring 5-40 mm with mesh opening angles (oa) ranging from 10 to 90°. We expected the majority of krill to encounter the trawl netting in random orientations due to high towing speeds and the assumed swimming capabilities of krill. However, our results indicated that size selectivity of krill is a well-defined process in which individuals encounter meshes at an optimal orientation for escapement. The simulation-based results were supported by data from experimental trawl hauls and underwater video images of the mesh geometry during fishing. Herein we present predictions for the size selectivity of a range of netting configurations relevant to the krill fishery. The methods developed and results described are important tools for selecting optimal trawl designs for krill fishing.

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Related in: MedlinePlus

Underwater images captured during fishing indicating escaping krill in the 15.4The escapees are marked with red arrows in the lower photo and clearly demonstrate an optimal orientation of the krill escaping. The photo is taken 10 meters in front of the cod line during commercial fishing.
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pone-0102168-g012: Underwater images captured during fishing indicating escaping krill in the 15.4The escapees are marked with red arrows in the lower photo and clearly demonstrate an optimal orientation of the krill escaping. The photo is taken 10 meters in front of the cod line during commercial fishing.

Mentions: The underwater recordings of escaping krill seem to indicate that they escape at the optimal attack angle perpendicular to the netting and head first (Fig. 12). This result demonstrates that the optimal FISHSELECT mode (i.e., CS1_CS2 with optimal orientation and attack angle) is a good approximation of the escape process. We therefore based our predictions of size selectivity of krill in trawls with other mesh sizes on this approximation and used only the optimal orientation (CS1_CS2).


Size selection of Antarctic krill (Euphausia superba) in trawls.

Krag LA, Herrmann B, Iversen SA, Engås A, Nordrum S, Krafft BA - PLoS ONE (2014)

Underwater images captured during fishing indicating escaping krill in the 15.4The escapees are marked with red arrows in the lower photo and clearly demonstrate an optimal orientation of the krill escaping. The photo is taken 10 meters in front of the cod line during commercial fishing.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126659&req=5

pone-0102168-g012: Underwater images captured during fishing indicating escaping krill in the 15.4The escapees are marked with red arrows in the lower photo and clearly demonstrate an optimal orientation of the krill escaping. The photo is taken 10 meters in front of the cod line during commercial fishing.
Mentions: The underwater recordings of escaping krill seem to indicate that they escape at the optimal attack angle perpendicular to the netting and head first (Fig. 12). This result demonstrates that the optimal FISHSELECT mode (i.e., CS1_CS2 with optimal orientation and attack angle) is a good approximation of the escape process. We therefore based our predictions of size selectivity of krill in trawls with other mesh sizes on this approximation and used only the optimal orientation (CS1_CS2).

Bottom Line: However, our results indicated that size selectivity of krill is a well-defined process in which individuals encounter meshes at an optimal orientation for escapement.The simulation-based results were supported by data from experimental trawl hauls and underwater video images of the mesh geometry during fishing.The methods developed and results described are important tools for selecting optimal trawl designs for krill fishing.

View Article: PubMed Central - PubMed

Affiliation: DTU Aqua, Technical University of Denmark, Hirtshals, Denmark.

ABSTRACT
Trawlers involved in the Antarctic krill (Euphausia superba) fishery use different trawl designs, and very little is known about the size selectivity of the various gears. Size selectivity quantifies a given trawl's ability to catch different sizes of a harvested entity, and this information is crucial for the management of a sustainable fishery. We established a morphological description of krill and used it in a mathematical model (FISHSELECT) to predict the selective potential of diamond meshes measuring 5-40 mm with mesh opening angles (oa) ranging from 10 to 90°. We expected the majority of krill to encounter the trawl netting in random orientations due to high towing speeds and the assumed swimming capabilities of krill. However, our results indicated that size selectivity of krill is a well-defined process in which individuals encounter meshes at an optimal orientation for escapement. The simulation-based results were supported by data from experimental trawl hauls and underwater video images of the mesh geometry during fishing. Herein we present predictions for the size selectivity of a range of netting configurations relevant to the krill fishery. The methods developed and results described are important tools for selecting optimal trawl designs for krill fishing.

Show MeSH
Related in: MedlinePlus