Size frequency data - neritic tunas and seerfish

Each year, the IOTC Secretariat prepares a reference size data set for each IOTC species to provide information on the size composition of their catch in the IOTC area of competence. The data are collected on land by enumerators during unloading and transshipments and at sea by fishers and scientific observers from the IOTC Contracting Parties and Cooperating Non-Contracting Parties (CPCs) as per IOTC data requirements (IOTC Resolution 15/02). The data are submitted on an annual basis, mostly with the forms 4SF, and curated by the Secretariat for dissemination prior to the IOTC working groups. The most recent versions of the standardised size-frequency data sets are available for each individual species from the main IOTC data set webpage.

All code lists and a description of the contents are provided in the document "Size frequency data - Reference file" (IOTC-2023-WPNT13-DATA10).

Data processing

The document IOTC-2020-WPDCS16-16 describes the processing steps applied to the size data sets managed at the IOTC Secretariat:

1- Removal of all sizes reported with an interval larger than the maximum interval value (Size measurement features)

2- Conversion of all sizes into standard measurement type with reference to conversion methods available in IOTC-2022-WPNT12-DATA11

3- Distribution of the number of fish reported in intervals larger than the standard interval into equally spaced smaller intervals

4- Assignment of all standard lengths smaller than the minimum standard length class to the minimum standard length class

5- Removal of all standard lengths larger than the maximum standard length class.