Variation in acoustically measured abundance from repeated surveys of herring

A large concentration of wintering herring was surveys continuously with acoustics over 37 hours in a fjord in Northern Norway. 16 surveys of the same area were conducted. Total abundance and statistics were computed for each survey. Distribution graphs showd a clear diel variation, with deep daytim...

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Bibliographic Details
Main Authors: Huse, Ingvar, Ostrowski, Marek
Format: Report
Language:English
Published: 1998
Subjects:
VDP::Mathematics and natural science: 400::Zoology and botany: 480::Marine biology: 497
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920
Norway
Northern Norway
Online Access:http://hdl.handle.net/11250/100145
Description
Summary:A large concentration of wintering herring was surveys continuously with acoustics over 37 hours in a fjord in Northern Norway. 16 surveys of the same area were conducted. Total abundance and statistics were computed for each survey. Distribution graphs showd a clear diel variation, with deep daytime layers and more shallow night time distribution. Acoustically measured abundance at night was 50% of the daytime values. The results are discussed in terms of behaviour induced diel variation in acoustic backscattering, and potential influence on acoustic abundance measurements.

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