Migratory patterns and contribution of stocking to the population of European eel in Lithuanian waters as indicated by otolith Sr: Ca ratios

• Main Author: Shiao, J.-C.; Ložys, L.; Iizuka, Y.; Tzeng, W.-N.
• Language: English
• Published: 2006
• Subjects: Anguilla anguilla;European eel;migratory history;otolith microchemistry;stocking; Anguilla anguilla
• Online Access: http://ntur.lib.ntu.edu.tw/handle/246246/192781; http://ntur.lib.ntu.edu.tw/bitstream/246246/192781/-1/10.pdf

Otolith Sr:Ca ratios were examined to evaluate the contribution of the stocked eel Anguilla anguilla elvers, which have been stocked in Lithuanian waters and mixed with naturally recruited eels for several decades, to the native eel population. Stocked eels were identified by the freshwater signature (Sr:Ca ratios <2·24 × 10−3) on the otolith after the glass eel stage. Naturally recruited eels, that had migrated through the North and Baltic Seas, were characterized by an extended seawater and brackish-water signature (Sr:Ca ratios >3·23 × 10−3) after the glass eel stage. Of 108 eels analysed, 21 eels had otolith Sr:Ca ratio profiles consistent with stocking while 87 showed patterns of natural recruitment. The ages of naturally recruited eels arriving in Lithuanian fresh waters varied from 1 to 10 years, with a mean ± s.d. age of 5·2 ± 2·1 years. Eels from the inland Lake Baluošai were all freshwater residents of stocked origin. Stocked eels, however, accounted for only 20% of the eels from the Curonian Lagoon and 2% of eels sampled in Baltic coastal waters. This finding does not support the hypothesis that the eel fishery in the Curonian Lagoon depends mostly on stocking.