Development and testing of fish-retention devices for pots: transparent triggers significantly increase catch efficiency for Atlantic cod ( Gadus morhua )

Fish pots have lower catch efficiency than gillnets and trwls and, therefore, are rarely used for catching Atlantic cod ( Gadus morhua ) and similar species. Fish-retention devices (FRDs), non-return devices that permit fish to enter the pot while impending exit, reduce the pot exit rate and therefo...

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Bibliographic Details
Published in:ICES Journal of Marine Science
Main Authors: Chladek, Jérôme, Stepputtis, Daniel, Hermann, Andreas, Ljungberg, Peter, Rodriguez-Tress, Paco, Santos, Juan, Svendsen, Jon Christian
Format: Article in Journal/Newspaper
Language:English
Published: 2021
Subjects:
Catch efficiency
Fish-gear interaction
Fish pots
Fish-retention device
Passive fishing gear
Pot entry-to-exit ratio
atlantic cod
Gadus morhua
Online Access:https://orbit.dtu.dk/en/publications/86d85bc8-7d63-4b0a-8d5b-7da849b18606
https://doi.org/10.1093/icesjms/fsaa214
https://backend.orbit.dtu.dk/ws/files/222795780/ICESJMS_2020_373_Proof_hi.pdf
Description
Summary:Fish pots have lower catch efficiency than gillnets and trwls and, therefore, are rarely used for catching Atlantic cod ( Gadus morhua ) and similar species. Fish-retention devices (FRDs), non-return devices that permit fish to enter the pot while impending exit, reduce the pot exit rate and therefor can increase catches. Conventional FRDs, however, also reduce entry rate and may not improve catches. To increase pot-catch efficiency, we developed and tested a new trigger-type FRD, made of transparent acrylic glass, which we named acrylic fingers (AFs). AFs are almost invisible underwater and offer little resistance to entering cod. We compared AFs with Neptune fingers (NFs), a conventional trigger-type FRD with a distinct visual outline, by observing cod entry and exit rates through both triggertypes rigged to a pot in a net pen. Both trigger types significantly reduced exit rates compared with a funnel without triggers; however, NFs also reduced entry rates by visually deterring od. Specifically, AFs have higher entry-to-exit ratios and therefore improve catch efficiency. Combining AFs with funnels further increased catch efficiency. Thus, transparent acrylic triggers present a promising new approach to increasing pot-catch efficiency and may increase the uptake of the cod pot, an environmentally low-impact gear.

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