Tighter restrictions are to be introduced next month.
From 1 September the minimum catch-size for both lobsters and crabs will increases by 10mm to "ensure the long-term future of the industry".
In 2018, the brown crab fishery was worth about £1.18m to the island, while the lobster fishery brought in £600,000.
The changes are being introduced after Tynwald backed proposals put forward by the environment department last July.
Other changes will also see commercial licences restricted to those who can demonstrate a track record within the fishery.
Recreational licenses will be reviewed, with an annual cost of £10 being introduced from next July.
Environment minister, Geoffrey Boot said: "Unused licences were highlighted by the industry working group as being the single greatest barrier to developing effective long-term management, so we have developed a policy to address this.
"We have also created an industry forum for this sector. It is hoped that, like the Scallop Management Board, it will be effective in developing and recommending further measures that secure the future for this industry and the stocks they depend upon".
Full details of the changes can be seen here.
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