Perhaps a player could choose the type of fishing.
Longline,
Trolling,
Seine netting
Drift netting
Each could come at a different cost and would be equipped by fleet or ship, each would perform differently, and possibly favor different ports or conditions.
Perhaphs the cost could be the equipment, or maybe you would need to buy a licence or permit to used the method in each port.
For example.
Lvl 1 permit allows you to troll
Lvl 2 permit allows you to troll or seine
Lvl 3 permit allows you to troll, seine, or longline,
Lvl 4 permit allows you to troll, seine, longline or drift net.
Permits must be purchased by port