title: Do otolith annular structures correspond to the first freshwater entry for yellow European eels Anguilla anguilla in the Baltic countries?
abstract: To examine the relationship between freshwater entry and otolith annular structures, a total of 113 naturally recruited European eels Anguilla anguilla from Lithuania and Latvia that entered fresh water at least once were collected. In some individuals (8.3-11.3%), the first freshwater entry coincided with a dark check that was distinctly different from neighbouring annuli. In most individuals (81.7-84.9%), the first freshwater entry occurred on rings and increments indistinguishable from other annuli. For the remaining individuals (3.8-10%), the first freshwater entry did not correspond to any otolith ring, band or annulus. According to recent evidence, the observed high correspondence between the first freshwater entry and otolith annuli was more likely due to the movement into fresh water during winter when the annulus was deposited, rather than stress resulting from habitat change. Consequently, the age estimation based on otoliths might be less influenced by this habitat change during the yellow eel stage.
authors.affiliation: Institute of Fisheries Science, National Taiwan University, Taipei, 10617, Taiwan, ROC.
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Lin
authors.forename: J-C
authors.initials: JC
authors.lastname: Shiao
authors.forename: L
authors.initials: L
authors.lastname: Lozys
authors.forename: M
authors.initials: M
authors.lastname: Plikss
authors.forename: A
authors.initials: A
authors.lastname: Minde
authors.forename: Y
authors.initials: Y
authors.lastname: Iizuka
authors.forename: I
authors.initials: I
authors.lastname: Rasals
authors.forename: W-N
authors.initials: WN
authors.lastname: Tzeng
mesh_terms: D000811:Anguilla / Q000033:anatomy & histology*; D025041:Animal Migration; D000818:Animals; D017753:Ecosystem; D005260:Female; D005618:Fresh Water; D007844:Latvia; D008097:Lithuania; D008297:Male; D010037:Otolithic Membrane / Q000033:anatomy & histology*; D012621:Seasons