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Bouwmeester, René, 2018. Shedding light on alternative shrimp fishing : development of shrimp pots with a focus on selection, attraction and behaviour. Second cycle, A2E. Lysekil: SLU, Dept. Of Aquatic Resources

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Abstract

In search of a less destructive alternative to current shrimp fishing methods, both in terms of bycatch reduction and increasing shrimp-catch in pots, this study aims to analyse the catches and bycatches of different pot designs and alternative attractants for pot fishing on Northern shrimps (Pandalus bore-alis). There are three main objectives: (1. describe how the different pot de-signs and attractants affects shrimp catch and bycatch in abundance and composition, (2. describe how the different pot designs and attractants af-fects the shrimp size distribution of the catch, (3. Describe how the different pot designs and attractants affect the behaviour of shrimps and bycatch in-side the pot by means of underwater video recordings. These objectives were met by conducting an experimental fishing study in Gullmarsfjord, Sweden. As alternative attractant lights in the colours green, white and ultra violet (UV) were tested together with four different pot design. The pots with the larger oval entrances caught significantly more shrimp in CPUE in comparison to the pots with the plastic funnel entrances. In terms of bycatch no significant difference was found between pot designs. The use of lights as an alternative to herring as attractant resulted into a 3.1 times higher shrimp CPUE. However the attractants also effected the bycatch. Especially green light resulted in many gadoids in the bycatch, white light resulted in fewer gadoids than green light, but UV light was found to be the most selec-tive light with the best shrimp catch/bycatch ratio. The results from this study contributes to the development of fishing shrimps with pots by pre-senting how the tested methods increased shrimp catches and affected by-catches.

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Studien syftar till att utvärdera räkburar som ett mindre destruktivt alternativ till nuvarande räkfiskemetoder efter nordhavsräka ( Pandalus borealis ) i svenska vatten. Studien hade tre huvudmål: 1. att analysera fångst och bifångst i förhållande till burdesign och typ av attraktion; 2. att analysera storleksfördelning av räkor i förhållande till burdesign och attraktion; 3. att utföra beteendeanalys av fångst och bifångst genom medel av videoinspelningar under vatten från insidan av burar. Bur ett och tre hade den högsta räkfångsten, troligen på grund av de större, ovala, ingångarna. Användningen av ljus som ett alternativ till sill som attraktion resulterade i en 3,1 gånger högre räkfångst. I jämförelse visade sig att typ av attraktion ha större inverkan än burdesign när det kom till mängden fångad räka. Kombinationen av vitt ljus och sill gav det bästa resultatet, följt av vitt ljus och UV-ljus. Däremot påverkade varje kombination av attraktorer fångs-kompositionen av framför allt bifångstarter på eget sätt.

Main title:Shedding light on alternative shrimp fishing
Subtitle:development of shrimp pots with a focus on selection, attraction and behaviour
Authors:Bouwmeester, René
Supervisor:Ljungberg, Peter
Examiner:Bartolino, Valerio
Series:UNSPECIFIED
Volume/Sequential designation:UNSPECIFIED
Year of Publication:2018
Level and depth descriptor:Second cycle, A2E
Student's programme affiliation:None
Supervising department:(NL, NJ) > Dept. Of Aquatic Resources
Keywords:Northern shrimp, Pandalus borealis, shrimp pot, fishing, bycatch, gadoid, attract, green light, white light, UV light, LED light, underwater camera, video recording, behviour
URN:NBN:urn:nbn:se:slu:epsilon-s-9269
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-s-9269
Subjects:Aquatic ecology
Language:English
Deposited On:02 Mar 2018 12:26
Metadata Last Modified:22 Jan 2019 02:02

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