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Each year, the IOTC Secretariat prepares reference size-frequency datasets 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 IOTC Form 4SF, and curated by the Secretariat for dissemination prior to the IOTC working groups.
The document IOTC-2020-WPDCS16-16 describes the processing steps applied to the size-frequency data 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-2023-WPTT25(AS)-DATA13
3- Distribution of the number of fish reported in intervals larger than the standard interval (Size measurement features) into equally spaced smaller intervals
4- Assignment of all standard lengths smaller than the minimum standard length class to the minimum standard length class (Size measurement features)
5- Removal of all standard lengths larger than the maximum standard length class
6- Removal of data reported for areas not in the Indian Ocean
Dataset | Criterion | By species | By gear |
|---|---|---|---|
Size frequencies | Available according to standards | 0 | 0 |
Not available according to standards | 2 | 2 | |
Low coverage (<1 fish per tonne caught) | 4 | ||
Not available | 8 | ||
