Browsing ICES CM documents authored by IMR scientists (1949-2011) by Author "Johnsen, Espen"
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Diurnal variation models of bottom trawl survey catches parameterised by using commercial CPUE data
Johnsen, Espen (ICES CM Documents;2004/R:41, Working paper, 2004)Introduction: Diurnal variation is observed in almost all marine surveys and can cause biased abundance and length frequency estimates. Symmetric logistic models developed by Hjellvik et al. (2001) were utilized to ... -
When acoustics is not enough – towards a measurement of sandeel availability
Johnsen, Espen; Harbitz, Alf (ICES CM documents;2009/I:16, Working paper, 2009)Experimental surveys in the peak feeding season of sandeel (April-May) show that the abundance and geographical distribution of schooling lesser sandeels (Ammodytes marinus) can be acoustically measured, but the density ...