The tuna fishery of the Western and Central Pacific Ocean occurs for the greater part in waters under the sovereignty or jurisdiction of coastal States which qualify as small island developing States (sids); this fishery is managed by the Western and Central Pacific Fisheries Commission (wcpfc). On account of the majority they represent, the sids strive for the adoption of measures which would benefit them. This article discusses the effect of these measures which may give the impression that the delicate balance reached with the adoption of the losc between the rights of coastal States and other States is being upset; this can be regarded as a kind of ‘creeping jurisdiction’. Three issues are considered: the quasi-exemption of application of many rules by the sids, the issue of the application of the Convention in the various areas under national jurisdiction and the requirements for the exercise of navigational rights.