Residents or visitors?
Old data can yield new insights when approached from a new angle. Data from Masfjorden are elucidating the population ecology of coastal cod, saithe and pollack.
Masfjorden is one of better studied fjords in Norway, thanks to a project in 1980s-1990s run by Institute of Marine Research and University of Bergen. The goal was to understand the potential for sea-ranching of cod in western Norway. This involved extensive gill-netting in the fjord over several years. In the new paper published in the ICES Journal of Marine Science, we use these data to show that the role Masfjorden plays is very different for cod, pollack and saithe populations. Saithe use the fjord as a nursery ground, and mature saithe vanish from the fjord. Pollack, on the other hand, seem to be permanent residents of the fjord. Cod show an intermediate pattern, and may contain more stationary and more migratory components. Find out more — the paper is freely available through this free-access link!
Reference: Heino, M., T. Svåsand, J. T. Nordeide, and H. Otterå. 2012. Seasonal dynamics of growth and mortality suggest contrasting population structure and ecology for cod, pollack and saithe in a Norwegian fjord. ICES Journal of Marine Science 69:537-546. doi: 10.1093/icesjms/fss043.