Size Composition Data Format

Size composition datasets describe the length and weight frequency distributions of fish sampled from various fisheries.
They provide important biological information used in stock assessments, growth studies, and species composition analyses.
Each record summarizes the number of fish observed within a defined length or weight class, by gear, flag, species, and spatial cell.

Most size data reported to the Commission originate from observer programs and port sampling activities.
This section focuses exclusively on aggregate size data submitted as part of the annual data submission, and does not include observer data already submitted through standard observer reports — this avoids double counting of information.

Two dedicated templates are used for reporting:

• Length Composition Template
• Weight Composition Template

Both templates share common data fields describing the year, month, gear, flag, fleet, and location (latitude and longitude of the southwest corner of the spatial cell).

Preferred resolution:

• Temporal: Monthly (for all gears)
• Spatial:
  • Longline and Troll → 5° × 5°
  • Purse Seine, Pole-and-Line, and other gears (e.g., ringnet, handline, gillnet) → 1° × 1°

Units:

• Length → reported in centimetres (cm)
• Weight → reported in kilograms (kg)

Each record must also specify the measurement type, which allows the SPC Scientific Services Provider (SSP) to standardize and convert between length and weight measures for analysis.
A full list of valid measurement types is available in the reference tables.

Field formatting details

• Lengths must be reported in centimetres (cm); weights must be in kilograms (kg).
• Coordinates (latitude and longitude) must represent the southwest corner of the spatial cell.
• Spatial resolution must follow the gear-specific grid (5°×5° for longline/troll, 1°×1° for other gears).
• Indicate whether measurements are rounded up or down to the nearest unit.
• Clearly describe sampling and statistical methods, including:
  • Whether sampling occurred during fishing operations or at unloading.
  • Details of the sampling protocol.
  • Any adjustments made to the raw size data and the rationale for these.
• Report any operational changes in the fishery that could affect data interpretation but are not captured as data attributes.
• Ensure all measurement-type codes follow the approved reference table in Annex A.2.
• When citing methods, refer to the Brogan et al. (2002) Port Sampling Manual for detailed sampling procedures, species handling protocols, and estimation approaches commonly applied in SPC port sampling programmes.

Documents structure and data fields format

Size composition data are organized into two distinct categories — Length and Weight — each with its own template and documentation files.
This separation ensures clarity, consistent units, and traceability of updates.

CSV Data Templates

• Length Frequency Data Template
• Weight Frequency Data Template

Two templates are provided:

• Length Frequency Template
• Weight Frequency Template

These datasets form part of the annual data submissions to the Commission and must exclude any observer data already reported separately through observer programmes.

Length Frequency Data

This dataset contains aggregate length composition (frequency) data, summarizing the number of fish observed in each length class by gear, flag, species, and spatial cell.
Each record represents a unique combination of year, month, gear type, species, and spatial cell.

Example document – Length frequency

Field descriptions – Length frequency

Notes:

• Lengths (length_cm) must be reported in centimetres (cm) and represent the midpoint of each length class.
• The freq field records the number of fish within that class bin.
• Coordinate values (lat, lon) define the southwest corner of the spatial cell.
• The meas_type code identifies the type of measurement taken (e.g., Fork, Total, Lower Jaw Fork).
• Exclude any data already submitted through observer datasets.

Weight Frequency Data

This dataset contains aggregate weight composition (frequency) data, summarizing the number of fish by weight class for each fishery, species, and spatial cell.
Each record represents a unique combination of year, month, gear, flag, species, and spatial cell.

Example document – Weight frequency

Field descriptions – Weight frequency

Notes:

• Weights (sp_kg) must be reported in kilograms (kg) and represent the midpoint of each weight class.
• The freq field indicates how many fish fall within that weight class.
• Coordinate values (lat, lon) define the southwest corner of the spatial cell.
• The meas_type code specifies the type of weight measurement (e.g., Whole, Gutted, Dressed).
• Do not include observer data already reported separately through observer submissions.

References

Reference Table 1: Measurement codes, descriptions, and size data types (i.e., length or weight) for size data.

The commonly used types are in bold.

Reference Table 2: Vessel gear listing

Reference Table 3: List of Fleets