Dynamics of wintering Norwegian spring-spawning herring at the entrance to Tysfjorden, December 1996

Abstract

The entrance region to Tysfjorden was acoustically surveyed a total of eleven times during the December 1996 abundance survey of the spawning stock of Norwegian spring-spawning herring (Clupea harengus). The observations are summarized through maps of the distribution, vertical sections, and statistical measures of acoustic density in each of two strata. Experimental variograms are modeled, yielding parameter values that summarize the major properties of aggregation. The collective measures of density and aggregation portray a highly dynamic situation with strong diel variation but a general persistence of the fish distribution over the eleven days of its repeated observation.