ResearchResearch at Tokai

Research ExcellenceThe Ecology of Marine Biology Using DNA Analysis

A part-time job during his student days led to him researching the DNA of tuna and sharks

The field of molecular ecology in which Junior Associate Professor Kenji Nohara specializes is a comparatively new field of learning that uses such molecular biology methods as DNA analysis in the observation that is central to ecological research to elucidate previously unclear areas. Nohara is using DNA analysis to carry out various research projects on the ecology and evolution of marine biology ranging from basic research to application.

Nohara, who said, "When I was young I felt close to the ocean and liked living creatures," entered the Tokai University School of Marine Science and Technology after graduating from high school.

"When I was a student I belonged to the Aquatic Animal Applied Ecology Research Group and frequently dived in the ocean catching fish. Actually I am still serving as the advisor to this club."

He also worked part time at the lower-branch organization of the Japanese Fisheries Agency known as the Ocean Fisheries Research Center (currently National Research Institute of Far Seas Fisheries), which is adjacent to the Tokai University Shimizu Campus.

"At the National Research Institute of Far Seas Fisheries I experienced DNA analysis on tuna and sharks. That was very interesting to me and I took half a year off from university to experience a trip around the world on a deep sea tuna survey vessel of the Fisheries Agency."

He said his experience at this time relates to his current research.

DNA analysis is one step toward controlling illegal tuna fishing

Tuna is a fish Japanese people love. However, the decline of tuna due to overfishing is currently an international issue. The amount of tuna that can be caught in one year in each region and by each country is set, but in many cases those limits are not obeyed. For example, because it is difficult to tell just by looking where a tuna was caught, some fishing boat crews lie about the provenance of tuna when unloading them.

However, according to Nohara, "A tuna's DNA differs depending on the area of the ocean in which it lives, so by checking DNA it is possible to specify where a tuna was caught with a certain degree of accuracy."

Nohara is doing joint research with the Japanese Fisheries Agency and the National Research Institute of Far Seas Fisheries on exposing illegal tuna fishing using such DNA analysis.

Nohara is also approaching the breeding ecology of sharks, many aspects of which are not well understood, from the perspective of DNA analysis.

"Some 60 percent of shark species are viviparous, meaning their young are born from the mother's womb just like with humans. Some sharks have more than 100 babies in their womb at a time. However, for some species not all those baby sharks necessarily share the same father. So by analyzing the DNA of mother sharks and baby sharks, we can understand how many male sharks that mother shark mated with to create the baby sharks in her womb."

Surprisingly, the shark's breeding ecology is polyandrous. The overfishing of sharks needed to make the luxury dish shark fin soup is also a major issue. Nohara is using DNA analysis to identify females that should be given priority in conservation from the standpoint of conserving sharks, which have a long breeding cycle and are easily influenced by the fishing industry.

Clarifying the process of evolution of marine life in the coastal waters of Japan

Nohara is most interested in small fish found on rocky shores that migrate little, such as the goby and the Japanese fluvial sculpin. He said there are cases in which differences in DNA can be seen in the same species between the Sea of Japan and the Pacific Ocean.

"In the glacial period Korea and Kyushu shared a land border and the Sea of Japan was enclosed like a lake. There is said to be a lot of diversity in the marine life around the long Japanese archipelago that runs north to south and it is possible that one cause is the special environment of having had the Sea of Japan closed off. Species whose DNA differs greatly in the Sea of Japan from what is found in the Pacific Ocean can be said to be in the process of becoming a new species. Through DNA analysis I would like to clarify the process of the evolution of life in Japan's coastal waters," Nohara said excitedly.

"The important thing in researching living things is engaging in both field work and lab work. While stuck in the lab, you cannot see the development of the research," Nohara emphasized.

The question of how to use DNA analysis to clarify puzzles and issues actually observed in the behavior and ecology of living creatures is a matter of the researcher's sense. Nohara reportedly encourages students on a daily basis to "get out in the field and acquire a research sense," just as he did when he was a student.

Molecular biology has been developing dramatically in recent years and now anyone can easily read a nucleic acid sequence. However, that alone is nothing beyond data. Thinking about how this data can be put to use in research is the important question.

When asked about the future direction of his research, Nohara said, “I want to continue developing my research on the ecology and evolution of various living creatures by skillfully combining it with DNA analysis and ecological expertise gained from field work.".

Junior Associate Professor Kenji Nohara

Born in 1976 in Kochi Prefecture. After graduating from the Fisheries Department of the School of Marine Science and Technology, Tokai University, he completed a doctoral program specializing in marine bio resources in the Department of Bioscience, the Faculty of Biotechnology, Fukui Prefectural University.

Doctorate (biotechnology). After working as a supporting research staff member at the Japan Fisheries Research and Education Agency, he assumed his current post in 2011.