Browsing ICES CM documents authored by IMR scientists (1949-2011) by Author "Engås, Arill"

Now showing items 1-19 of 19

    • A method to reduce survey bottom trawl variability 

      Engås, Arill; Ona, Egil (ICES CM Documents;1991/B:39, Working paper, 1991)
      A technique for limiting the variability of trawl doorspread is described. In addition, modifications of trawling technique which enable the doors to stay upright and maintain constant ground contact under different ...

    • A new radio link telemetry positioning system, experiences from tracking of fish and crustaceans 

      Bjordal, Åsmund; Engås, Arill; Soldal, Aud Vold; Øvredal, Jan Tore (ICES CM Documents;1993/B:23, Working paper, 1993)
      Telemetry positioning systems based on hydrophone arrays have been used for different tracking applications. The main improvement of this new system is the wire-less transmission of signals from hydrophone - radio buoys ...

    • Acoustic abundance estimation of the stock of Norwegian spring spawning herring, winter 1995- 1996 

      Foote, Kenneth G.; Ostrowski, Marek; Røttingen, Ingolf; Engås, Arill; Hansen, Kaare A.; Hauge, Kjellrun Hiis; Skeide, Roar L.; Slotte, Aril; Torgersen, Øyvind (ICES CM Documents;1996/H:33, Working paper, 1996)
      Standard echo integration methodology has been applied to the stock of Norwegian spring spawning herring (Clupea harengus) wintering in the Ofotfjord-Tysfjord-Vestfjord system during late autumn 1995 and early winter ...

    • Avoidance reactions of ultrasonic tagged cod during bottom trawling in shallow water 

      Engås, Arill; Soldal, Aud Vold; Øvredal, Jan Tore (ICES CM Documents;1991/B:41, Working paper, 1991)
      Introduction: Observations made by echo sounder (Ona 1988) have shown that cod (Gadus morhua L.) may avoid an approaching survey vessel horizontally and vertically. However, there has been a lack of information on the ...

    • Catch comparison between rockhoppers and bobbins ground gear on the Norwegian bottom sampling trawl 

      Engås, Arill; Jacobsen, Jan Arge; Soldal, Aud Vold (ICES CM Documents;1988/B:31, Working paper, 1988)
      In a study aimed at improving the reliability of the Norwegian bottom sampling trawl, comparative fishing between standard bobbins gear and rockhopper ground gear were carried out in the Barents Sea. The catch ratios ...

    • Day / night variation in fish directivity in the trawl opening 

      Huse, Ingvar; Aglen, Asgeir; Engås, Arill; Godø, Olav Rune; West, Charles W. (ICES CM Documents;1994/B:18, Working paper, 1994)
      Still photographs of fish in the mouth area of a bottom trawl were taken by a downwards-oriented automated strobe camera mounted near the headrope. Fish angles relative to the towing direction were measured. Fish were ...

    • Density dependent catchability in bottom trawl surveys 

      Aglen, Asgeir; Engås, Arill; Godø, Olav Rune; McCallum, Barry R.; Stansbury, Don; Walsh, Stephen J. (ICES CM Documents;1997/W:16, Working paper, 1997)
      Fish form schools, layer or patches in which the individual fish's behaviour is not independent of its neighbours movements. On the other hand, at low densities fish may have the freedom to act as single individuals ...

    • Development of a species-selective trawl for demersal gadoid fisheries 

      Engås, Arill; West, Charles W. (ICES CM Documents;1995/B+G+H+J+K:1, Working paper, 1995)
      An experiment was carried out to test a prototype species-selective bottom trawl for separating cod from haddock, secondarily saithe, in the Norwegian commercial roundfish fisheries. A sorting system incorporating a ...

    • Diurnal changes in bottom trawl catches and vertical fish distribution 

      Engås, Arill; Jacobsen, Jan Arge; Soldal, Aud Vold (ICES CM Documents;1988/B:32, Working paper, 1988)
      Bottom sampling trawl catches and acoustic abundance estimates of North-East Arctic cod and haddock in the Barents Sea were collected and examined according to time of day. The trawl catches were at average larger by day ...

    • Experiences using the constraint technique on bottom trawl doors 

      Engås, Arill; Ona, Egil (ICES CM Documents;1993/B:18, Working paper, 1993)
      The constraint technique, i.e. using a rope between the warps, has the intention of minimizing the variability in trawl geometry with depth. Experiments with the constraint technique on two different bottom trawls used ...

    • In situ determination of bottom trawl ground gear contact 

      Engås, Arill; Ona, Egil; Ramberg, Kjell (ICES CM documents, Working paper, 2001)
      Exact definition of towed distance with proper ground gear contact is an essential parameter in bottom trawl swept area estimates of fish abundance. Errors in this key parameter may lead to a first order bias in abundance ...

    • Near-bottom sampling with bottom and pelagic trawls 

      Engås, Arill; Godø, Olav Rune (ICES CM Documents;1987/B:15, Working paper, 1987)
      The Institute of Marine Research, Bergen, has carried out combined bottom trawl and acoustic surveys for cod and haddock in the Barents Sea - Svalbard area since 1981. These investigations have demonstrated clearly that ...

    • Preliminary results of investigations on escapement of fish under the fishing line of a Norwegian sampling trawl 

      Engås, Arill; Godø, Olav Rune (ICES CM Documents;1986/B:30, Working paper, 1986)
      The Institute of Marine Research, Bergen, has carried out combined bottom trawl and acoustic surveys for cod and haddock in the Barents Sea and the Svalbard areas since 1981. These investigations have clearly demonstrated ...

    • Scale damage and survival of cod and haddock escaping from a demersal trawl 

      Soldal, Aud Vold; Isaksen, Bjørnar; Marteinsson, Jon Einar; Engås, Arill (ICES CM Documents;1991/B:44, Working paper, 1991)
      Cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus L.) escaping through the meshes of a cod-end (135 mm diamond meshes) or through a metal grid sorting device mounted in the foremost part of the cod-end, were ...

    • Swept area variation with depth and its influence on stratified trawl surveys indices on Arcto-Norwegian cod 

      Engås, Arill; Godø, Olav Rune (ICES CM Documents;1986/D:18, Working paper, 1986)
      Stratified trawl surveys have been carried out in the Barents Sea and the Svalbard areas since 1981. Based on the assumption of a constant area swept by the trawl during a standard trawl haul at any depth, swept area ...

    • The effect of different sweep lengths on length composition of bottom sampling trawl catches 

      Engås, Arill; Godø, Olav Rune (ICES CM Documents;1987/B:16, Working paper, 1987)
      Abundance estimates of North-east Arctic cod and haddock are given annually on the basis of combined bottom trawl and acoustic surveys. Both survey methods use data from bottom trawl catches in the calculations. The ...

    • The probability of cod (Gadus morhua) and ling (Molva molva) to encounter gillnets based on in situ fish movements 

      Engås, Arill; Jørgensen, Terje (ICES CM Documents;1997/W:17, Working paper, 1997)
      The probability of cod (Gadus morhua) and ling (Molva molva) to encounter a fleet of four gillnets (110m) set within a fixed survey area of 600x600 m2 and soaked for a period of 12 h (1800-0600 hrs) is calculated on the ...

    • Vertical distribution of cod, haddock and redfish; Impact on bottom trawl and acoustic surveys in the Barents Sea 

      Aglen, Asgeir; Engås, Arill; Huse, Ingvar; Michalsen, Kathrine; Stensholt, Boonchai K. (ICES CM Documents;1997/Y:16, Working paper, 1997)
      At a selected location in the Barents Sea acoustic observations, bottom- and pelagic trawl catch data were collected over a 10 day period. A large proportion of the fish were in the acoustic dead zone during the sampling ...

    • Vertical entrance into a trawl of Barents Sea gadoids as studied with a two level fish trawl 

      Valdemarsen, John Willy; Engås, Arill; Isaksen, Bjørnar (ICES CM Documents;1985/B:46, Working paper, 1985)
      Catch figures of different demersal species(cod, haddock, saithe etc.) in the cod-ends of a two level trawl were examined using variable height of the separating panel (0.5, 0.75, 1.0 and 1.5 m). Cod enters the trawl ...