You need a fisshing "FLEET" to support a fishing industry. You need cold stores, and staff to man them, to export overseas. You have to go and market your product to the Asian countries, like Japan for instance. Your product has to be first class, and supply has to be reliable.
Big tuna are iced down in special containers, and air-freighted to Japan live. Does Manus have an International sized airport to do this? This is the high value end of the fishin,g worth thousands of dollars a fish, for the Sashimi market. The japanese will pay top price for the right product.
Show me your infrastructure, your marketing department, your logistics and administartiv staff. I know some expatriate, uni educated Manuusians, who could probably organise this, but would they want to? I think it would ber too frustratinhg for them.
Last but not least. Where is your funding for this project? You would need about $30M for the infrastructure, plus your fishing fleet. Let's assume the boats are all privately owned, for the exercise. You would need the port faciities then, to handle the catch quickly, and get it to the cold store. Then you would need the transport, and the roads, to do so.