• Tuna purse seiners are large purse seiners, normally over 45 metres, equipped to handle large and heavy purse seines for tuna. They have the same general arrangement as the American seiner, with the bridge and accommodation placed forward. A crows nest or tuna tower is positioned at the top of the mast, outfitted with the control and manoeuvre devices. A very heavy boom which carries the power block is fitted at the mast. They often carry a helicopter to search for tuna schools. On the deck are three drum purse seine winches and a power block, with other specific winches to handle the heavy boom and net. They are usually equipped with a skiff.