Biodiversity is very high around Japan, with more than 4,000 fish species. Of these, hundreds of fish species are sold in the market. Japan’s diet and food culture are supported by a wide variety of marine life, including not only fish but also shellfish, crustaceans, and algae. This diversity is the most important point of the fishing industry that is not found in the agriculture and livestock industries.
For the sustainable use of these diverse and abundant marine resources in the future, it is important to properly manage the abundance. Because any marine organism is a member of the ecosystem, the management requires not only resource information, such as the amount, distribution, age, and size composition of the single resource species but also information on the environments and the organisms surrounding them. However, it is very difficult for us to know where and how many organisms live in the water. Current marine product surveys often use nets to capture target organisms and estimate the amount (concentration) based on the amount obtained, the hauling speed, and the size of the net mouth. When investigating marine organisms in coastal areas, we sometimes dive in the water and visually count the number of target organisms. Fishermen, on the other hand, use a fish sonar to confirm the presence of the fish. However, research using these methods requires not only a great deal of time and energy but also specialized knowledge for fish classification, as well as special equipment and techniques for capturing the fish. Thus, survey opportunities and the data obtained from the surveys are limited. In addition, the results of the surveys may vary depending on the investigator, investigation equipment, and investigation method, and the results often lack credibility. Environmental DNA analyses have attracted attention in recent years as a new research method to overcome these problems.