Concurrent recruitment failure in gadoids and changes in the plankton community along the Norwegian Skagerrak coast after 2002

• Published in: ICES Journal of Marine Science
• Main Authors: Johannessen, Tore, Dahl, Einar, Falkenhaug, Tone, Naustvoll, Lars J.
• Format: Text
• Language: English
• Published: Oxford University Press 2012
• Subjects: The Mid-Northeast Atlantic and North Sea; Johannessen; Northeast Atlantic
• Online Access: http://icesjms.oxfordjournals.org/cgi/content/short/69/5/795; https://doi.org/10.1093/icesjms/fsr194

<qd> Johannessen, T., Dahl, E., Falkenhaug, T., and Naustvoll, L. J. 2012. Concurrent recruitment failure in gadoids and changes in the plankton community of the Norwegian Skagerrak coast after 2002. – ICES Journal of Marine Science, 69: 795–801. </qd>Since 1919, annual beach-seine sampling has been carried out along the Norwegian Skagerrak coast with the main objective of measuring the abundance of 0-group gadoids. Repeated incidents of abrupt and persistent recruitment collapses in gadoid populations have been observed locally. These collapses have been linked to gradual eutrophication, which has resulted in abrupt changes in the plankton community and deprivation of adequate prey for 0-group fish. Since 2002, the recruitment of 0-group gadoids has been very poor along the Skagerrak coast on a regional scale. At the same time, major changes in the plankton community have been observed. A regular and pronounced autumn bloom dominated by red-tide forming dinoflagellates such as large Ceratium spp. and the toxic Karenia mikimotoi has practically vanished, and a linear decrease in oxygen concentration at intermediate depths (30 m) that has been evident since the 1960s, was reversed around 2002. These changes would normally indicate improved environmental conditions. However, the recruitment failure in gadoids does not support this perception. Rather, the evidence points towards a potential shift in the plankton community that has resulted in gadoid recruitment failure.