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dc.contributor.authorSteingrund, Petureng
dc.date.accessioned2009-12-18T09:09:38Z
dc.date.available2009-12-18T09:09:38Z
dc.date.issued2009-10-02eng
dc.identifier.isbn978-82-308-797-2 (print version)en_US
dc.identifier.urihttp://hdl.handle.net/1956/3697
dc.description.abstract1. This thesis aims to explain why there was a near-collapse of the Faroe Plateau cod stock in the 1990s and why it recovered so quickly. Contrary to what local people on the Faroes believe, these fluctuations were not explained by large-scale migrations between, e.g., Icelandic and Faroese fishing grounds, but rather by local processes on the Faroe Plateau. When cod were in poor condition they moved towards land and hampered the survival of 1-year-old cod, probably by displacing 1-year-old cod to normal cod-depths where they were cannibalised. The survival of 2- year-old cod was, however, positively correlated with the total contemporary biomass of age 3+ cod, probably caused by reduced predation mortality or enhanced foraging, up to an abundance of around 100 thousand tonnes of age 3+ cod, above which there was a sharp decline. 2. There was no negative correlation between the stock size of cod and the individual growth rate. Cod seemed to be reluctant to enter the food-rich deep waters (> 150 m) indicating that the shallower areas had to be ‘filled up’ first before cod moved to deep waters. Cod in shallow waters fed on sandeels, juvenile Norway pout and benthic crustaceans, whereas cod in deep waters mostly fed on adult Norway pout and Blue whiting. Cod in good condition tended to have a larger stomach content than slim cod, and, in deep waters, there was a positive correlation between feeding success and local cod density. 3. Cod tended to be caught on longlines when in poor condition, coinciding with a low feeding on natural prey organisms and a more pronounced feeding migration. Hence, the total fishing mortality, which was overall very high, tended to vary negatively with the individual growth rate. 4. The information in 1-3 indicated that a low ecosystem productivity during the late 1980s combined with a high fishing mortality were the main reasons why the cod fishery nearly collapsed in the 1990s. The recovery was likely caused by favorable environmental conditions and a low fishing mortality. A simulation study strongly suggested that the cod fishery on the Faroe Plateau is not sustainable and that the stock will probably collapse in the future. An immediate reduction of the fishing mortality of 40-60% could reverse the negative trend and result in an optimal harvesting. However, the common belief among Faroese fishermen / local people in the existence of large-scale migrations of fish, and a reluctance to accept short-term reductions in catch rates, may represent major obstacles in rebuilding the Faroe Plateau cod stock.en_US
dc.language.isoengeng
dc.publisherThe University of Bergenen_US
dc.relation.haspartPaper I: Steingrund, P.; Hansen, B.; Gaard, E., 2005, Cod in Faroese waters, pp. 50-55. In: Brander, K (ed.), Spawning and life history information for North Atlantic cod stocks, ICES Cooperative Research Report, No. 274. Copyright 2005 International Council for the Exploration of the Sea. Used with the kind permission of the International Council for the Exploration of the Sea. Published version. The published version is also available at: <a href="http://www.ices.dk/products/cooperative.asp" target="_blank"> http://www.ices.dk/products/cooperative.asp</a>en_US
dc.relation.haspartPaper II: Steingrund, P.; Reinert, J.; Henriksen, A.; Pedersen, M.; Reinert, R., 2009, Diet and habitat use of cod (Gadus morhua) at the Faroes influenced by prey density, cod density, size, and condition. Full text not available in BORA.en_US
dc.relation.haspartPaper III: Fróðskaparrit (Annales Societatis Scientarum Færoensis) 53, Joensen, J. S.; Steingrund, P.; Henriksen, A.; Mouritsen, R., Migration of cod (Gadus morhua): tagging experiments at the Faroes 1952-1965, pp. 100-135. Copyright 2005 Fróðskapur – Faroe University Press. Reproduced with permission. Published version.en_US
dc.relation.haspartPaper IV: Steingrund, P.; Mouritsen, R., 2009, Faroe Plateau cod (Gadus morhua L.) distribution and migration during 1997-2006. Full text not available in BORA.en_US
dc.relation.haspartPaper V: ICES Journal of Marine Science 2010 67(1), Steingrund, P.; Mouritsen, R.; Reinert, J.; Gaard, E.; Hátún, H., Total stock size and cannibalism regulate recruitment in cod (Gadus morhua) on the Faroe Plateau, pp. 111-124. Copyright 2009 International Council for the Exploration of the Sea. Published by Oxford Journals. Full text not available in BORA due to publisher restrictions. The published version is available at: <a href="http://dx.doi.org/10.1093/icesjms/fsp240" target="_blank"> http://dx.doi.org/10.1093/icesjms/fsp240</a>en_US
dc.relation.haspartPaper VI: ICES Journal of Marine Science 62(2), Steingrund, P.; Gaard, E., Relationship between phytoplankton production and cod production on the Faroe shelf, pp. 163-176. Copyright 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. Full text not available in BORA due to publisher restrictions. The published version is available at: <a href="http://dx.doi.org/10.1016/j.icesjms.2004.08.019" target="_blank">http://dx.doi.org/10.1016/j.icesjms.2004.08.019</a>en_US
dc.relation.haspartPaper VII: ICES Journal of Marine Science 67(1), Steingrund, P.; Ofstad, L. H., Density-dependent distribution of Atlantic cod (Gadus morhua) into deep waters on the Faroe Plateau, pp. 102-110. Copyright 2009 International Council for the Exploration of the Sea. Published by Oxford Journals. Full text not available in BORA due to publisher restrictions. The published version is available at: <a href="http://dx.doi.org/10.1093/icesjms/fsp230" target="_blank"> http://dx.doi.org/10.1093/icesjms/fsp230</a>en_US
dc.relation.haspartPaper VIII: Fisheries Research 100(3), Steingrund, P.; Clementsen, D. H.; Mouritsen, R., Higher food abundance reduces the catchability of cod (Gadus morhua) to longlines on the Faroe Plateau, pp. 230-239. Copyright 2009 Elsevier B.V. Full text not available in BORA due to publisher restrictions. The published version is available at: <a href="http://dx.doi.org/10.1016/j.fishres.2009.08.002" target="_blank"> http://dx.doi.org/10.1016/j.fishres.2009.08.002</a>en_US
dc.relation.haspartPaper IX: Steingrund, P.; Ofstad, L. H.; Olsen, D., 2003, Effect of recruitment, individual weights, fishing effort, and fluctuating longline catchability on the catch of the Faroe Plateau cod (Gadus morhua L.) in the period 1989-1999, pp. 418-420. In: Turell, W.; Lavin, A.; Drinkwater, K. F.; St. John, M.; Watson, J., Hydrobiological variability in the ICES area, 1990-1999, ICES Marine Science Symposia, No. 219. Used with the kind permission of the International Council for the Exploration of the Sea. Published version.en_US
dc.relation.haspartPaper X: Jákupsstovu, S. H. í; Reinert, J.; Steingrund, P., 2004, Cod in Faroese Waters, pp. 40-53. In: Bjordal, Å.; Gjøsæter, H.; Mehl, S. (eds.), Management strategies for commercial marine species in northern ecosystems, IMR/PINRO Joint Report Series, No. 1. Reproduced with permission. Published version. The published version is also available at: <a href="http://www.imr.no/filarkiv/2004/12/Imr-Pinro-1-2004.pdf/nb-no" target="_blank">http://www.imr.no/filarkiv/2004/12/Imr-Pinro-1-2004.pdf/nb-no</a>en_US
dc.relation.haspartPaper XI: Journal of Marine Science 2008 65(1), Pampoulie, C.; Steingrund, P.; Stefánsson, M. Ö.; Daníelsdóttir, A. K., Genetic divergence among East Icelandic and Faroese populations of Atlantic cod provides evidence for historical imprints at neutral and non-neutral markers, pp. 65-71. Copyright 2007 International Council for the Exploration of the Sea. Published by Oxford Journals. Full text not available in BORA due to publisher restrictions. The published version is available at: <a href="http://dx.doi.org/10.1093/icesjms/fsm181" target="_blank">http://dx.doi.org/10.1093/icesjms/fsm181</a>en_US
dc.titleThe near-collapse of the Faroe Plateau cod (Gadus morhua L.) stock in the 1990s: The effect of food availability on spatial distribution, recruitment, natural production and fisheryen_US
dc.typeDoctoral thesis
dc.rights.holderPetur Steingrunden_US
dc.subject.nsiVDP::Landbruks- og Fiskerifag: 900::Fiskerifag: 920nob


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