Researchers at the Japan Agency for Marine-Earth Science and Technology, the University of Tokyo, and the Fisheries Research and Education Agency have developed a method for unraveling the "life history of fish" by analyzing the nitrogen isotope ratio of the crystalline body in the eyeballs of fish.
It is not easy to grasp "when and in which sea" a fish that travels three-dimensionally over a long distance in a vast ocean space.On the other hand, the amino acid phenylalanine cannot be synthesized in the body of fish and can only be obtained by feeding, so analysis of its nitrogen isotope ratio is useful for estimating the foraging history.In addition, since each sea area has a unique nitrogen isotope ratio, it is also useful for identifying the sea area where fish are distributed.
In particular, the crystalline lens in the eyeball of a fish begins to form when the fish is in the egg, and as it grows, it forms an additional layer like the annual ring of a tree, which is retained throughout life.In this study, we thought that the life history of fish could be clarified in chronological order by peeling the crystalline lens like an onion skin, collecting it for each growth layer, and analyzing the nitrogen isotope ratio of accumulated phenylalanine. Is.
This time, using this method, we tried to decipher the life history of the 1-year-old chub mackerel collected off the coast of Sanriku from the fry stage.As a result, a total of 34 layers of samples were obtained, and by time-series nitrogen isotope ratio analysis, the larvae were spent in the subtropical waters (near the offshore of the Izu Peninsula) where the nitrogen isotope ratio was low, and the nitrogen isotope ratio was high as they grew. It is said that it was possible to restore the typical excursion route of Masaba, which is said to move to the subcold waters (toward off Sanriku).
This method is expected to be an epoch-making tool that can obtain ecological information such as fish movement and foraging history at the highest time resolution in the world.Since it can be applied to many marine organisms with a crystalline lens, it is expected to play an important role in future marine ecological research and fishery resource management.