Frontiers in Marine Science (Nov 2015)
First results of mass marking of European eel (Anguilla anguilla) with alizarin red and SrCl2 in Estonia
Abstract
European eel (Anguilla anguilla) has one of the most intriguing life cycles of all fishes. Its larvae drift in the early stages of the species life as well as the spawning run in the maturity stretches to thousands of kilometres, from Europe to Sargasso sea. In between the eel may inhabit both brackish- and freshwater systems. Due to different natural and anthropogenic factors, the eel stocks have been in decline all over Europe for decades. That’s why a thorough research of its origin, migration and growth rate is essential. In Estonia, the freshwater eel stocks derive almost exclusively from a stocked origin. The biggest inland waterbody, L. Võrtsjärv (270km2) has had a restocking program since the 1950s. Since 2002, eels are have been stocked into smaller lakes in the area such as L. Saadjärv (707ha), L. Kuremaa (497ha), L. Kaiavere (250ha) and L. Vagula (519ha). To measure the effectiveness of the stocking, growth rates and the migration of the eels, a mass-marking project was carried out in 2014 and continues in 2015. In the spring of 2014, 135000 glass eels were marked with 0,15 g/L alizarin red (Sigma-aldrich A5533) at ~ 15°C water temperature. 34 of them were analysed for the successfulness of the marking. In the summer of 2014, 193636 elvers (Tw 3.5g-50g) were marked with SrCl2. 30567 of them meant for stocking into smaller lakes were also marked with 0,15g/L alizarin red. 36 specimens have been analysed for the Sr-marking effectiveness and 40 out of these also for alizarin marking effectiveness. Preliminary results from otoliths indicate efficiency of both methods.
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