Around £20 million (€29.4 million / $35.4 million) was lost after the failures of local fish-farming consortium SSG Seafoods, fish processors Shetland SeaFish and drill cuttings processor Shetland Offshore Environmental Services, the report said.
The Standards Commission for Scotland said Sandy Cluness had not broken the councillors' code of conduct after an investigation which was launched last year, according to the report.
An independent inquiry was launched after a petition containing 2,000 signatures was received demanding the investments into aquaculture, fish processing and oil service companies be scrutinized.
