However, since then the dynamic fisherman, who is as comfortable in the circles of power in Adelaide as he is on a fishing boat, has surprised the market and even himself with the growth of a Clean Seas sideline business - kingfish farming.
The kingfish success has helped the Clean Seas share price rise from the float price of 50c to $1.81 last night, while the serious business of attempting to breed tuna continues.
While academics have for years described aquaculture as an industry of the future, Mr Stehr is gaining widespread respect for his ability to achieve progress.
The kingfish harvest has grown from a weekly 300kg to 50 tonnes worth $500,000 a week and is marching towards 200 tonnes a week in the next few years.
Kingfish Farming Nets Profit
AUSTRALIA - When Port Lincoln seafood magnate Hagen Stehr floated Clean Seas Tuna in late 2005, the market was sceptical. Fish farming, breeding tuna and a Port Lincoln tuna fisherman were all fairly new to the stock market.