A fisheries administration must control the compliance with fishing effort regimes in geographical areas where maximum allowable fishing effort applies.

Without prejudice to special rules, where a fishing vessel carrying on board or, where appropriate, deploying a fishing gear or gears subject to a fishing effort regime or operating in a fishery subject to a fishing effort regime crosses during the same day two or more geographical areas subject to that fishing effort regime, the fishing effort deployed shall be counted against the maximum allowable fishing effort related to such fishing gear or such fishery and to the geographical area in which the largest proportion of time was spent during that day.

Where a F2fisheries administration has authorised a fishing vessel in accordance with Article 27(2) to use more than one fishing gear or gears belonging to more than one grouping of fishing gears subject to a fishing effort regime during a certain fishing trip in a geographical area subject to that fishing effort regime, the fishing effort deployed during that trip shall be counted simultaneously against the maximum allowable fishing effort available F3... and related to each of such gears or groupings of fishing gears and to such geographical area.

Where fishing gears belong to the same grouping of fishing gears subject to the fishing effort regime, the fishing effort deployed in a geographical area by fishing vessels when carrying those gears on board shall be counted only once against the maximum allowable fishing effort related to such grouping of fishing gears and to such geographical area.

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A day present within an area shall be any continuous period of 24 hours or part thereof during which a fishing vessel is present within the geographical area and absent from port or where appropriate deploying its fishing gear. The time from which the continuous period of a day present in the area is measured is at the discretion of F5a fisheries administration. A day absent from port shall be any continuous period of 24 hours or part thereof during which the fishing vessel is absent from port.