Astthorsson, O. S., Valdimarsson, H., Gudmundsdottir, A., and Óskarsson, G. J. 2012. Climate-related variations in the occurrence and distribution of mackerel (Scomber scombrus) in Icelandic waters. – ICES Journal of Marine Science, 69: . Based on long-term investigations on sea temperature in Icelandic waters, five climatic periods are defined from the mid-1880s until today. These are a cold period between 1880 and 1920, a warm period between 1921 and 1964, a cold period between 1965 and 1971, one of intermediate conditions (alternating warm and cold) between 1972 and 1995, and finally a warm period from 1996 until today. Mackerel were first reported from Icelandic waters in 1895, were then found intermittently until 1996, and from then appeared almost every year and since 2007 in large numbers in many areas around Iceland. The occurrence of mackerel appears to be confined mainly to warm periods in the North Atlantic Ocean and around Iceland. The unprecedented occurrence and extended distribution of the species began at the onset of the recent warm period during the mid-1990s and, in recent years, 0-group and age 1 mackerel have also been observed in Icelandic waters. This expansion in distribution resulted initially in a bycatch fishery, which then developed into a direct fishery within the Icelandic Exclusive Economic Zone, increasing from ∼1700 t in 2006 to ∼120 000 t in 2009 and 2010.
Harvest control rules have become an important tool in modern fisheries management, and are increasingly adopted to provide continuity in management practices, to deal with uncertainty and ecosystem considerations, and to relieve management decisions from short-term political pressure. We provide the conceptual and institutional background for harvest control rules, a discussion of the structure of fisheries management, and brief introductions to harvest control rules in a selection of present day cases. The cases demonstrate that harvest control rules take different forms in different settings, yet cover only a subset of the full policy space. We conclude with views on harvest control rules in future fisheries management, both in terms of ideal and realistic developments. One major challenge for future fisheries management is closing the gap between ideas and practice.
Jensen, A. J., Ó Maoiléidigh, N., Thomas, K., Einarsson, S. M., Haugland, M., Erkinaro, J., Fiske, P., Friedland, K. D., Gudmundsdottir, A. K., Haantie, J., Holm, M., Holst, J. C., Jacobsen, J. A., Jensås, J. G., Kuusela, J., Melle, W., Mork, K. A., Wennevik, V., and Østborg, G. M. 2012. Age and fine-scale marine growth of Atlantic salmon post-smolts in the Northeast Atlantic. – ICES Journal of Marine Science, 69: 1668–1677. Surface trawls were conducted over a large area of the Northeast Atlantic in 2002, 2003, 2008, and 2009 to collect samples of Atlantic salmon (Salmo salar) post-smolts during their marine feeding migration (n = 2242). The dominant smolt age of wild post-smolts was 2 years, followed by 1- and 3-year-old fish, and a few 4-year-old fish. The average rate of circulus formation in the marine zone of scales was estimated to be 6.3 d circulus−1. Both the age structure and the number of marine circuli in the scales suggest that the majority of the post-smolts originated in rivers in southern Europe. Applying intercirculi distances in scales as a proxy variable of growth rate suggests that putative marine growth rates varied among years, with the fastest growth rates in 2002 and the slowest growth rates in 2008. Further, the first marine intercirculi distances were narrowest in 1-year-old smolts, successively increasing with smolt age, indicating that growth rates during the first period at sea were lowest for salmon of southernmost origin. Growth indices are linked to prevailing environmental and biological conditions.
Óskarsson, G. J., Gudmundsdottir, A., and Sigurdsson, T. 2009. Variation in spatial distribution and migration of Icelandic summer-spawning herring. – ICES Journal of Marine Science, 66: 1762–1767. The distribution of the fishable stock of Icelandic summer-spawning herring (Clupea harengus L.) and the overwintering grounds have changed with fishing seasons from 1978/1979 through 2006/2007. The possible causes investigated include variation in sea temperatures, stock size, and annual recruitment. The stock collapsed as a result of overfishing and environmental changes during the late 1960s, since when the spawning stock has gradually increased, from 11 kt in 1972 to 800 kt in 2006. These changes coincided with geographic variation in its distribution. We identify five phases, based on a graphic analysis and the centre of gravity of the fishery. Investigations on a large geographic scale gave no clear indication that sea temperature has affected the distribution. Changes were also not clearly related to stock size or year-class strength. The distribution change in the late 1990s may be partly explained by year classes adopting a new migration pattern when entering the fishable stock.
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