Otolith Sr:Ca Ratios as Natural Mark to Discriminate the Restocked and Naturally Recruited European Eels in Latvia

• Main Author: Lin, Yu-Jia;Shiao, Jen-Chieh;Plikshs, Maris;Minde, Artis;Iizuka, Yoshiyuki;Rashal, Isaak;Tzeng, Wann-Nian
• Format: Conference Object
• Language: English
• Published: 2011
• Subjects: Anguilla anguilla
• Online Access: http://ntur.lib.ntu.edu.tw/handle/246246/258254; http://ntur.lib.ntu.edu.tw/bitstream/246246/258254/2/lin.pdf

The restocking programs of the European eel Anguilla anguilla have been conducted for nearly one century in Latvia. To evaluate the efficiency of the eel restocking program and reveal the migratory life histories of European eels in Latvian waters, a total of 75 individuals were collected from the mouth of River Daugava (Daugavrgriva, brackish), nearby lake (Lake Ķīšezers,freshwater), and a coastal site (Mērsrags, brackish). The naturally-recruited eels consisted of two saltwater type individuals (SW, 0–7%): eels lived in saltwater and did not enter freshwaters, and inter-habitat-shifter (IHS, 60–85%): eels had experienced both freshwater and saltwater. The restocked eels consisted of purely freshwater type (FW, 7–36.7%) that the eels permanently lived in freshwater without saltwater experience. Average otolith Sr:Ca ratios in the edge were different among sites and origins, and corresponded to the salinities of sampling sites. The mean age at first freshwater entry of IHS was 4.8 ± 2.3 years, similar to previous study in Lithuania (p = 0.188). The growth rates of FW eels in the river mouth and coast were significantly slower than that of IHS eels (p < 0.001 and 0.012), but not in the lake (p = 0.372), implying a site-origin interaction on the growth rate. The use of otolith Sr:Ca ratios as a natural mark to distinguish the restocked eels enabled the assessment of restocking efficiency in the future.