Krill Module 1 - Full Model

Displayed unit

Total biomass

Whole-area density

Abundance

Mean krill TL

Swarms

Survey estimate

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Choose the management units and their densities at left, then press Generate field .

Each unit is built, stratified against GEBCO bathymetry and surveyed; the figures are drawn only after that finishes.

Subarea 48.1 candidate krill fishery management units, with GEBCO bathymetry setting the coastal/oceanic split. Biomass is estimated per unit and summed.

Management units

Subarea 48.1 candidate krill fishery management units (CCAMLR CKFMU, WG-EMM-2024).

Set each unit by

Density (g/m2) Total biomass (t) Number of swarms

Mean column density per unit. Defaults are WG-EMM-2022 Table 1; biomass is density x area and the swarm count follows.

Target biomass per unit. Density is biomass / area and the swarm count follows.

How many swarms the unit really holds. Biomass is that count times the typical literature swarm, and density follows. The cap below still limits how many are drawn.

SSIW

EI

BS

JOIN

GS

Biomass is estimated per unit and summed, never by averaging densities across units.

Coastal/oceanic depth (m)

Max swarms drawn per unit

The depth breakpoint splits each unit into coastal and oceanic strata using GEBCO bathymetry, and each stratum draws its own swarm priors. The cap limits how many swarms are drawn: a capped field carries the unit's whole biomass in proportionally larger swarms, so the census total is right but a survey of it samples far fewer, larger targets than the real field holds.

Random seed

Swarm settings

Swarm clustering

Clustering index (daughters per parent)

Cluster radius (m)

Sequential parent/daughter placement. An index of 0 gives uniform random positions; the radius is the scatter SD of daughters about their parent.

Swarm geometry and density

Lognormal means and SDs, by bathymetric stratum. Defaults are the literature priors; the coastal/oceanic split is set by the depth breakpoint above.

Coastal mean

Coastal SD

Oceanic mean

Oceanic SD

Length (m)

Width (m)

Height (m)

Centre depth (m)

Internal density (g/m3)

Krill settings

Krill growth

Growth variant

Von Bertalanffy (basal curve)

Linf (mm)

k

t0 (yr)

Basal curve after Thannassekos et al. 2021 (SC-CAMLR SAM-2021/12, GRYM 48.1). The sex-specific variant uses Kawaguchi et al. 2007 (MEPS 345: 199-210) and is fixed by that source, so its coefficients are not editable here.

Cohort mix

Relative frequency of each age cohort. Renormalised, so only the ratios matter.

Small (1-2 yr)

Medium (3-5 yr)

Old (4-6 yr)

Sex ratio and length-weight

Proportion male

Between-swarm SD

Beta-distributed per swarm. Length-weight is fixed at Skaret et al. 2023: W = 2.236e-6 x TL^3.314 (TL in mm, W in g). A sex-specific length-weight variant is not implemented -- no sex-resolved coefficients have been sourced.

Survey (swath transect)

Swath width (m)

Depth cap (m)

Transect spacing (nm)

Along-track step (m)

The transect sweeps the full length of the area in a band of the chosen width, integrating krill from the surface to the depth cap (or the seabed). Each along-track step is one reported sample: its footprint is width x step, so density is footprint biomass divided by that area (g/m2) and abundance is krill per m2. At a 2 m width and 1 m step the footprint is 2 m2, i.e. density = biomass/2.

Editing any setting above takes effect on the next Generate field.

Analyses

Fills SWARM Tables 2 and 3 and the TRANSECTS spacing results. Runs many paired replicate fields on the displayed unit, so start low.

Replicates

Selected units

Survey design: WG-ASAM-2026/09
Build: 2026-08-07 22:45 UTC