4.—(1) Subject to paragraph (2) below this article applies to any fishing boat other than one to which article 3 above applies and which–
(a)measures more than 20 metres between perpendiculars or more than 24 metres in overall length, and
(b)is within the Scottish zone.
(2) This article does not apply to such a fishing boat which–
(a)operates exclusively within the territorial sea of the state in which it is registered or whose flag it flies, or
(b)which never spends more than 24 hours at sea taken from the time of departure to the time of return to port.
(3) A satellite tracking device shall–
(a)be installed, and
(b)be maintained fully operational,
on a vessel to which this article applies.