| Summary: | In January 1996 the stock of Norwegian spring-spawning herring (Clupea harengus) was acoustically surveyed in the wintering area. Both immature and mature fish were present. Because of the comparative lateness of the survey, the spawning migration had already begun, and the total survey area extended from the inner reaches of Ofotfjord and Tysfjord to the sea area southwest of Vestfjord, well over 200 nautical miles from end to end. Coverage of the Vestfjord area alone occupied three days, thus also including diurnal vertical migration. The evident complex of dynamics is described in two ways: (1) by acoustic images of herring distribution in vertical sections of Vestfjord, and (2) through variograms computed for strata identified by the visual presentation. Speculation is offered on the use of such an analysis in stratification.
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