Standard protocols for the analysis of school based data from echo sounder surveys

This paper presents a set of standard extraction parameters and protocols for the use of image analysis techniques in the processing of echo sounder data. The paper includes parameters at the school, elementary distance sampling unit (EDSU) and regional levels. The school level parameters, which are mainly derived from the image analysis, fall into four main categories: positional, morphometric, energetic and environmental. At the sampling unit level (i.e. standard integration units, commonly 1 or 2.5 nautical miles), parameters used include: school structures, protocols for including layers and general scatter plus ancillary (e.g. environmental) variables. These variables are derived mostly from visual examination of the echogram and from ancillary data collected underway. Regional level parameters include those mapped from point samples (e.g. trawls) or which are available as maps. Each school thus has its own unique parameters and is associated with an EDSU and through that to regional data. We discuss the application of such databases to the analysis of echo surveys at a school level in relation to aggregation patterns (school, school cluster and population) and to changes in those aggregation patterns with stock biomass and exploitation pattern.

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