A second site is expected to be operational in 2021 and will provide a further four jobs on the island, which is currently home to around 350 people.
Both farms were unanimously supported by Stronsay community council, following a public consultation.
More than 165 people out of Orkney's 22,100 population directly work in the salmon farming sector with hundreds more jobs supported through the supply chain.
Four of the five new roles at Cooke's new Mill Bay site have gone to local recruits, allowing people like teenager Johnny Smith to stay on the island where he has grown up.
Johnny's currently a pupil at Kirkwall Grammar School and is being supported by Cooke to finish his studies before starting his full-time career as a fish farmer later this year.
Johnny said: "I'm staring as a casual worker until the summer and then I'll become a full-time member of the team.
"There are not that many career opportunities on the island so it's great to know that I have a long-term career which lets me stay on Stronsay before I've left school.
"Cooke has got a really good reputation on the island. I've already done some maritime skills course through the NAFC Centre and have qualifications in sea survival and first aid. Salmon farming is totally new to me but I'm keen to get stuck in."
Other new recruits include former creel fishermen who bring a wealth of knowledge and experience in working at sea.
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