MEPS 325:181-186 (2006)  -  doi:10.3354/meps325181

Concurrent temporal patterns in light absorbance and fish abundance

Tom A. Sørnes*, Dag L. Aksnes

Department of Biology, University of Bergen, PO Box 7800, 5020 Bergen, Norway

ABSTRACT: The abundance of midwater fishes in fjord basins, as well as the abundance and size of mesozooplankton, have previously been related to optical properties of the basin water. Herein, we report on concurrent temporal changes in light absorbance and fish abundance for Masfjorden and modest changes in both variables for Lurefjorden and Sognefjorden, western Norway. The inverse relationship between fish abundance and absorbance in the temporal data, spanning 9 yr, is consistent with the relationship previously described for spatial data representing different fjords. The combination of salinity and oxygen accounted for 94% of the observed variance in absorbance of the 3 fjords, and we suggest that these variables serve as proxies for regional and local determinants of absorbance in fjord basins, respectively. While salinity indicates basin water origin and its optical properties, oxygen is a measure of turnover time and local degradation of organic matter, presumably affecting absorbance.

KEY WORDS: Light absorbance · Fish abundance · Fjords

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