As most fisheries managed by RFMOs are fully subscribed, there is little room for carrying out new incremental activities in established fisheries within such structures. As a result, existing or new idle capacity may become engaged in IUU activities8 unless prevented through domestic and international legal and fisheries policy frameworks. To ensure sustainable fisheries on the high seas it is therefore important that states co-operate both with respect to managing fish stocks on the high seas and to ensure that idle domestic fishing capacity is not being inappropriately transferred to the high seas or to other states.