Blar i forfatter Artikler, rapporter og annet (Norges fiskerihøgskole) "Santos, Juan"

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    • Broadening the horizon of size selectivity in trawl gears 

      Stepputtis, Daniel; Herrmann, Bent; Mieske, Bernd; Santos, Juan (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-12)
      The discussion of alternative harvest patterns in commercial fisheries has been raised by stock assessment and fishery modelers, especially in the wider context of balanced harvesting. But often, these theoretical approaches propose alternative exploitation patterns that are difficult to achieve within the current limitations in the selectivity characteristics of fishing gears, such as trawl gears. ...

    • The capability of square-meshes and fixed-shape meshes to control codend size selection 

      Bak-Jensen, Zita; Santos, Juan; Melli, Valentina; Stepputtis, Daniel; Feekings, Jordan P.; Herrmann, Bent (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-11)
      Trawl codends are commonly made of diamond-mesh netting. However, diamond-mesh codends vary in mesh geometry along its length and during fishing due to catch build up. This introduces variability in the size selection process. This phenomenon compromises the rationality of regulating exploitation patterns in trawl fisheries through adjustments in codend mesh size. One technical solution often ...

    • Catch and release patterns for target and bycatch species in the Northeast Atlantic deep-water shrimp fishery: Effect of using a sieve panel and a Nordmøre grid 

      Larsen, Roger B.; Herrmann, Bent; Sistiaga, Manu Berrondo; Brinkhof, Jesse; Santos, Juan (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-21)
      The Nordmøre grid and the sieve panel are two of the main devices used to reduce fish bycatch in trawl fisheries targeting shrimp species. However, even when using such devices, some small-sized fish enter the codend of the trawl together with the targeted shrimp. Therefore, bycatch reduction remains a problem in some shrimp fisheries. One such fishery is the Northeast Atlantic deep-water shrimp ...

    • Catch pattern and size selectivity for a gear designed to prevent fish injuries during the capture process in a North-East Atlantic demersal trawl fishery 

      Herrmann, Bent; Sistiaga, Manu; Larsen, Roger B.; Brinkhof, Jesse; Gjøsund, Svein Helge; Jacques, Nadine; Santos, Juan (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-04)
      In the North-East Atlantic demersal trawl fishery targeting cod and haddock, the interest on fishing gear designs that preserve fish quality and welfare has grown. However, the gear configurations tested so far imply practical challenges, therefore, more user-friendly designs are still sought by the industry. For a new design to be considered, it needs to have size selective properties that are at ...

    • The effect of Nordmøre grid length and angle on codend entry of bycatch fish species and shrimp catches 

      Larsen, Roger B.; Sistiaga, Manu Berrondo; Herrmann, Bent; Brinkhof, Jesse; Tatone, Ivan; Santos, Juan (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-18)
      The Nordmøre grid is regarded as an efficient bycatch reducing device and is used in various shrimp trawl fisheries globally. However, in some shrimp fisheries bycatch remains a problem that seriously impacts commercial trawl activities. This study tested and compared the performance of two versions of the Nordmøre grid in the Northeast Arctic Deepwater Shrimp (Pandalus borealis) fishery; a standard ...

    • The efficiency of sieve-panels for bycatch separation in Nephrops trawls 

      Santos, Juan; Herrmann, Bent; Mieske, Bernd; Krag, Ludvig Ahm; Haase, Stefanie; Stepputtis, Daniel (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-11)
      This study investigated the efficiency of a sieve‐panel concept, intended to separate bycatch species from <i>Nephrops</i> (Norway lobster) in a trawl gear via mechanical and behavioural means. Four different designs of varying panel mesh size or inclination were tested in experimental fishing. For each design, the length‐dependent sieving efficiency, defined as the fraction of <i>Nephrops</i> or ...

    • How many fish need to be measured to effectively evaluate trawl selectivity? 

      Herrmann, Bent; Sistiaga, Manu Berrondo; Santos, Juan; Sala, Antonello (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      The aim of this study was to provide practitioners working with trawl selectivity with general and easily understandable guidelines regarding the fish sampling effort necessary during sea trials. In particular, we focused on how many fish would need to be caught and length measured in a trawl haul in order to assess the selectivity parameters of the trawl at a designated uncertainty level. We also ...

    • Is there a limit to the potential effects of shortening lastridge ropes on the size selectivity of diamond mesh codends? 

      Sistiaga, Manu; Herrmann, Bent; Brinkhof, Jesse; Larsen, Roger B.; Santos, Juan; Stepputtis, Daniel; Brinkhof, Ilmar; Jacques, Nadine; Cerbule, Kristine; Petetta, Andrea; Cuende, Elsa; Kvalvik, Liz Beate Kolstad (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-21)
      Shortening codend lastridge ropes can be an effective fishing gear modification to improve the size selection properties in diamond mesh codends. Lastridge ropes attached to codend selvedges withstand the longitudinal forces created by the catch building up and therefore, prevent the codend meshes from closing. However, the extent to which the lastridge ropes should be shortened to maximize the ...

    • Predictive framework for codend size selection of brown shrimp (Crangon crangon) in the North Sea beam-trawl fishery 

      Santos, Juan; Herrmann, Bent; Stepputtis, Daniel; Gunther, Claudia; Limmer, Bente; Mieske, Bernd; Schultz, Sebastian; Neudecker, Thomas; Temming, Axel; Hufnagl, Marc; Bethke, Eckhard; Kraus, Gerd (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-16)
      The brown shrimp (<i>Crangon crangon</i>) fishery is of great socio-economic importance to coastal communities on the North Sea. The fishery is exploited by beam trawlers often using codends with very small mesh sizes, leading to concerns about catch rates of undersized shrimp. However, little information is available on codend size selection, making it difficult to provide scientifically based ...

    • Quantification of gear inflicted damages on trawl-caught haddock in the Northeast Atlantic fishery 

      Sistiaga, Manu; Herrmann, Bent; Brinkhof, Jesse; Larsen, Roger B.; Jacques, Nadine; Santos, Juan; Gjøsund, Svein Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-12)
      External damages are indicators of the overall quality of fish and fish welfare. Haddock is an important commercial species widespread in the North Atlantic, but few studies related to quality have been carried out on this species. We studied the levels of external damages on haddock captured with a demersal trawl in the Northeast Atlantic. Further, we investigated to what extent the compulsory ...

    • Quantifying the performance of selective devices by combining analysis of catch data and fish behaviour observations: methodology and case study on a flatfish excluder 

      Santos, Juan; Herrmann, Bent; Stepputtis, Daniel; Kraak, Sarah B. M.; Gökce, Gökhan; Mieske, Bernd (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-06)
      This article describes a method for the quantitative analysis of fish behaviour relative to selection devices in trawl gears. Based on video observations, the method estimates probabilities for a given event to happen and establishes behavioural tree diagrams representing and quantifying behavioural patterns in relation to the selection device under assessment. Double bootstrapping is used to account ...