Senator Minihan also raised the licensing of tank boats for herring and mackerel. These are large and efficient vessels which can land hundreds of tonnes of fish on each fishing trip. For more than a decade the general policy has been that the boats can be introduced to the fleet only by withdrawing a similar type of boat from the fishing fleet. The policy is a recognition that the available quotas are decreasing and a reflection of the decline of the stocks. If new vessels are introduced, old ones must be taken out. The future policy for licensing these vessels is being reviewed in light of that.