A research group led by Associate Professor Takeshi Tomiyama of Hiroshima University and Senior Researcher Michio Yoneda of the Fisheries Research and Education Agency Setonaikaiku Suisan Research Institute has found that the reproductive power of Ikanago is directly affected by the feeding conditions more than half a year ago. Proven experimentally.
Sand lance is a fish that is popular as a nail boiled in the eastern part of the Seto Inland Sea in the spring.Ammodytes lanceolata born in winter accumulates nutrients while growing from spring to summer, and lays eggs after summer-winter dormancy (aestivation).In recent years, the catch in the Seto Inland Sea has decreased significantly, but the cause has not been clarified.
The research group investigated the effects of nutrient accumulation up to aestivation on maturity and spawning.Ammodytes lanceolata caught in the Seto Inland Sea are bred from May to July under two feeding conditions (satiated amount and 2% of it are fed daily).After a container containing sand was placed in the water tank to put the sand lance to aestivation, it was collected regularly from November to January, and the body size, maturity, and number of eggs were investigated.
As a result, when the amount of food is 25% of the amount of satiety, the average size is reduced by about 22%, and about 2% of unmature individuals appear.In addition, it was found that the number of eggs increases according to the body length under the satiety condition, but the number of eggs hardly increases even if the body length increases under the condition of 25%.
Until now, in the fishing industry, the idea that the amount of eggs laid can be secured by leaving a certain amount of parent fish has been used for resource management.However, from the above results, it was clarified that whether or not sand lance can accumulate sufficient nutrients by summer affects the rate of participation in spawning as a parent in winter and the amount of spawning when becoming a parent.
This result is expected to be an important achievement for understanding the resource change mechanism of sand lance, and to contribute to the study of new resource management measures to secure the spawning volume of sand lance.
Paper information:[PLOS ONE] Food availability before aestivation governs growth and winterreproductive potential in the capital breeding fish, Ammodytes japonicus
