The Shetland Islands Regulated Fishery (Scotland) Order (also known as a Regulating Order) came into force in 1999. The Shetland Shellfish Management Organisation (SSMO) was set up in 2000 and was granted the legal right to manage the Regulating Order. There have since been another two Regulating Orders with the current one being conferred on SSMO until 2028.

SSMO, therefore, manages the commercial shellfish fisheries between tide line and the 6 mile limit around the coast of Shetland. These fisheries are for lobsters, crabs, scallops, queens, whelks, clams, razorshells, cockles, mussels and oysters. Amongst other things, the Regulating Order give the SSMO the power to impose restrictions and regulations, to issue licences and the right to set tolls.

The SSMO is a partnership of organisations with an interest in the future of Shetland's shellfish fisheries. The organisation is legally constituted as a company limited by guarantee and is run by a board of directors, most of whom are active fishermen. The SSMO Board membership has been restructured over the years and currently comprises 12 directors as follows:

2 members from the Association of Shetland Community Councils (nominated by the association) - currently Lindsay Laurenson and Alastair Cooper, who is also the new chair. A third independent director is Sam Laurenson, a mussel farm workboat skipper, selected in December 2023 following an open recruitment process.

2 shellfish processors - currently Robert Williamson, who is vice-chair, and George Hirbakis.

2 Shetland Fishermen's Association (SFA) members (nominated by the SFA Small Boat Committee) - currently Richard Gray and James John Shearer.

5 SSMO licencees (nominated and voted for by SSMO members) - currently Sydney Johnson, Billy Reid, Richard Grains, Karl Dalziel and Jerry Pottinger.

The SSMO Board meet 6 times a year and there is also a SSMO Advisory Group which meets on a regular basis and advises the SSMO Board.

Since 2012 the SSMO has held Marine Stewardship Council (MSC) Accreditation for its sustainable fisheries for king scallops and brown crab.

The SSMO is considered nationally to be a leader in inshore fisheries management.