Short communicationOld timers from the Baltic Sea: Revisiting the population structure and maximum recorded age of ide Leuciscus idus

- Population age structure of ide was complex and varied between sites.
- A new maximum age of 29 years was recorded for ide using otolith thin sections.
- Growth in length practically ceased at ca 10 years of age.
- Higher growth rates were recorded compared to historical datasets from the same region.
- Highly positive relationship between age and otolith weight was observed.

Population age structure of ide Leuciscus idus in the eastern Baltic Sea was investigated using samples from three sites in the Väinameri Sea. Using the otolith thin sections for the first time on ide otoliths, a new maximum age of 29 years was observed. It is suggested that otolith thin sections should be preferred to scales if clear-cut and accurate age determinations of ide are desired. The results demonstrated that ide population in the Baltic Sea may consist of individuals with more variable age range than previously reported. There was a significant difference in adult age structure among study sites (spawning stocks), which was also reflected in the overall abundance of ide in the particular site. Higher growth rates were recorded compared to historical datasets collected from the same region. A strong positive relationship between age and otolith weight was observed. Potential factors behind the differences in age structure and abundance among study sites are discussed.