In collaboration with Hokkaido University, Ehime University discovered fossil fish scales of sardines that have reached the past 2800 years from the seafloor sediments of Beppu Bay.It was the longest record of continuous fish population fluctuations in the world.
One-sixth of the world's catch is sardines.In the world's leading fishing grounds, when the number of sardines decreases, the catch of anchovy increases, and when the number of anchovy decreases, the number of sardines increases.The world's food supply is stable due to the change of fish species every few decades.However, due to the collapse of the anchovy stock off the coast of Peru, which has the largest catch in the world, the recovery of the catch of Japanese anchovy, which was the highest in the world in the past (fish species change off the coast of Japan is about every 6 years), is the world's food resource. It is said to have a great influence on the future of the world.
To predict the dynamics of sardines, it is necessary to confirm the stability of long-term fish species change by investigating seafloor sediments.In the waters around Japan, fish species change appears most clearly in the world, but there is no record of seafloor sediments so far, and its stability is unknown.
This time, the research team discovered scales of sardines and anchovy in the seafloor sediments of Beppu Bay, Oita Prefecture.Long-term fluctuations in fish populations have been clarified from the annual sedimentation records of fish scales over the past 2800 years.It is the longest record in the world for continuous fish population fluctuation records.
The records often showed decades of sardine and anchovy variability, but the time to indicate fish species change was short.Rather, long-term records show 100-year fluctuations and long-term declining trends, and there are various fluctuation patterns other than the fish species changes observed in the 20th century, and the stock of sardines is not stable. rice field.
The cause of the instability is unknown at this stage, but further understanding of the response of sardines to past climate change is expected to provide a solid future forecast for fish stocks.
