The reviewer is right. The first sector is a macro conception of agriculture. It indeed includes fishery. However, the data of output and employment are both collected on this level - the first sector. Hence, we assume the quotient of the two variables is a proxy to agriculture labor productivity. Meanwhile, they are the only available data on the prefectural level to calculate agricultural labor productivity. Therefore, we think this calculation is still helpful.
Labor productivity needs to be measured using real value of agricultural output.