It means that improvements, which are often short-lived, cannot be used by policymakers to increase fishing opportunities beyond reasonable levels.
Más rud é gur dearadh, gur cuireadh i bhfeidhm agus gur cloíodh leis an bplean i gceart, ní mór go bhfanfadh leibhéal na bithmhaise cobhsaí, ar a laghad, nó níos fearr arís dul chun cinn a dhéanamh ó bhliain go chéile.