About biomass estimation

Echoview can apportion integrated backscatter data to individual species and estimate the density of those species within a domain of analysis. This feature is available when exporting analyses from echograms or scenes.

Preparation

Before biomass can be estimated you must define regions, region classes and species to suit your needs. Echoview provides a default region class and a default species with default properties, but it is important that you adjust these to suit your environment.

Species are defined and allocated to region classes on the Classes page of the EV File Properties dialog box.

Region classes are assigned to regions using either:

the Region Browser dialog box,
the (3D Object) Properties dialog box (3D regions only)
the Region Editor dialog box, or
the Region classification tool (2D regions only).

Notes:

Bad data types and no-data may be handled in different ways (for integration). For more information refer to About samples and echo integration.
An line pick can create a bottom line to represent an integration boundary for biomass estimation. Be aware that the accepted Backstep for biomass estimation is -0.50 meters.

Estimating Biomass from single beam data

For single beam data the biomass estimates are exported from echograms.

Two analysis variables for estimating biomass are available for export. Each species within each region (and optionally within each cell) has:

Density_number = The number of individual specimens of this species per unit of water surface area (see units below)

Density_weight = The total weight (mass) of this species per unit of water surface area (see units below)

These are exported only if selected on the Export page of the EV File Properties dialog box and only when exporting integration analyses of regions (Integration by Regions or Integration by Regions by Cells).

Notes:

You can use the Motion correction (Dunford method) operator to improve your biomass estimate. This operator corrects sample values for the effects of pitch and roll. See About motion correction for more information.
Density_number and Density_weight require a species TS value, this may be provided by an in situ TS estimation or a TS estimation from other sources (such as trawl fish-length to TS relationships).

Estimating Biomass from Multibeam data

For multibeam data the biomass estimates are available from scenes.

Four analysis variables for estimating biomass are available for export. Each species within each region has:

Density_number = The number of individual specimens of one species per unit of water volume (see units below)

Density_weight = The total weight (mass) of one species per unit of water volume (see units below)

Fish_number = The number of individual fish of one species in the volume of water contained within a region.

Fish_weight = The total weight of fish of one species in the volume of water contained within a region.

The species to which these four variables apply is identified by the species_name exported along with these variables.

Units

When analyzing single beam data, Echoview makes these analysis variables available per square nautical mile or per hectare. The preferred unit can be set using the Biomass area units box on the Export page of the EV File Properties dialog box.

When analyzing multibeam data these analysis variables are available per cubic meter only.

About biomass estimation

Preparation

Estimating Biomass from single beam data

Estimating Biomass from Multibeam data

Units

See also