Tuna buyers should not buy immature tuna (especially Skipjack < 1,5 kgs.) at any extend. In West Afrika – mainly Ivory Coast – is a market for small size Skipjack, but this is not the case in other oceans. It will make the boatowners reluctant to let their boats fish on all tuna that moves!
For the boatowners, if you keep landing small Skipjack, the buyers/canners will always find an excuse to pay lower prices too for the other tuna which is mature and more valuable.