This dataset lists fishing efforts targetting tuna and tuna-like species from the Indian Ocean Tuna Commission (IOTC) by longliners from 1952 to 2015. Efforts are stratified by year, month, fishing gear, vessel flag reporting country, unit of effort, area (mainly 5° squares). It corresponds to the effort part of the IOTC catch-and-effort (task2) dataset.

Efforts are expressed in several units : Number of days at sea, number of fishing days, number of hooks, number of sets. The unit of effort depends on the stratum (i.e. association of the year, fishing gear, vessel flag reporting country). Only one single unit of effort is available for a given stratum.

This dataset was downloaded on the IOTC website. It was then restructured to be in line with the Sardara database structure (columns normalization, names, etc.). However the content of data and the code lists were kept exactly as their are available in the source dataset.

The description below (caracteristics, specific issues and problems that need to be taken into account) is extracted from the IOTC web page where the dataset has been downloaded.

Caracteristics, specific issues and problems that need to be taken into account :

Catches and effort are not available for all Nominal catches strata. When recorded, the catches in these datasets might represent the total catches of the species in the year for the fleet and gear concerned or represent simply a sample of those. These data are considered to be in the public domain, provided that the catch of no individual vessel can be identified within a time/area stratum. In cases when an individual vessel can be identified, the data are aggregated prior to release by time, area or flag to preclude such identification, and will then be in the public domain. Catch-and-effort and length-frequency data grouped at a finer level of time-area stratification are only released with written authorization from the sources of the data and are subject to a number of constraints destined to preserve confidentiality.