5:15 PM - 6:30 PM
[HTT21-P11] Tracing of the freshwater fish movement patterns and water dynamics by strontium stable isotope ratios and the elements concentrations analysis
Keywords:strontium stable isotope ratio, otolith, fish, water
First, we investigated the relationship between the 87Sr/86Sr of three-spined stickleback whole otoliths (ear bone) and the water in isolated water bodies. We confirmed that both water and fish have almost same 87Sr/86Sr.
Second, by analyzing the water of different rivers and tributaries in Otsuchi, we found that, just in one tributary of Kozuchi mainstream, 87Sr/86Sr and many element concentrations (e.g. Ca, Sr) were remarkably different between the upstream and downstream. Using 87Sr/86Sr and Sr concentration values of water, the downstream water was estimated to be mix of the upstream water, mainstream water and seawater (Contribution ratio; upstream: 82.6%, mainstream: 16.7%, seawater: 0.6%).
Then, using 87Sr/86Sr and elemental concentration of otoliths of fish captured in the upstream and downstream, we estimated their past movement patterns. We compared the water 87Sr/86Sr between the upstream and the downstream and the 87Sr/86Sr of otolith. As a result, it was possible to identify that stickleback lived in either upstream or downstream within single tributary; three-spined sticklebacks captured in the upstream (40 individuals in total) were not likely to move from downstream, while the fish caught at downstream (13 individuals in total) were estimated to have moved from the upstream or the mainstream. Furthermore, in the downstream, some fish otoliths showed a larger value of Sr/Ca than the others, which means that those fishes lived in high salinity environment in the past suggesting that the downstream population of three-spined stickleback was able to live in both fresh and brackish water environments.