Inshore migration and otolith microstructure/microchemistry of anguillid glass eels recruited to Iceland |
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Authors: | Mari Kuroki Momoko Kawai Bjarni Jónsson Jun Aoyama Michael J Miller David L G Noakes Katsumi Tsukamoto |
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Institution: | (1) Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo 164-8639, Japan;(2) Institute of Freshwater Fisheries, Northern Division, 550, Saudárkrókur, Iceland;(3) Department of Zoology and Axelrod Institute of Ichthyology, University of Guelph, Guelph, ON, NIG 2WI, Canada;(4) Present address: Department of Fisheries and Wildlife, Oregon Hatchery Research Center, Oregon State, University, Corvallis, OR 97331-3803, USA |
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Abstract: | The timing of catches of anguillid glass eels and their otolith microstructure and microchemistry were studied in southwest
Iceland, where the European eel, Anguilla anguilla and American eel, A. rostrata have been thought to live sympatrically, to learn about their early life history and the possible mechanism of the separation
between these two species ranges. Catches at the site studied suggest that glass eels may have started upstream migration
as the river temperature warmed in late June and early July. The glass eels were mitochondrially identified into two species,
A. anguilla and A. rostrata, although the latter were likely hybrids between the two species based on a different study. Otolith analyses showed no sharp
increases in otolith increment width or sharp decrease of otolith Sr:Ca ratio in either species, which are the characteristic
changes corresponding to the onset of metamorphosis in many anguillid species including A. rostrata collected in North America and A. anguilla in Europe. The mean age at recruitment determined for the glass eels in Iceland were similar between the two species (336.6 ± 41.7
and 319.3 ± 36.0 days for A. anguilla and A. rostrata, respectively), as were their total lengths (range 58.0–78.5 mm and 58.5–73.0 mm). In addition, mean age at metamorphosis
(278.0 ± 36.8 and 254.0 ± 47.7 days) and total age (372.3 ± 50.8 and 352.9 ± 42.6 days) were also similar between the two
species. However, these ages of A. rostrata in Iceland were older than those in North America, and those of A. anguilla collected in Iceland were roughly intermediate between the rest of Europe and North Africa. These findings support the hypothesis
that the timing of metamorphosis is a key factor for determining the place of recruitment of glass eels and maintaining the
geographic separation between the two species. |
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Keywords: | Freshwater eel Recruitment Metamorphosis Otolith microstructure Otolith microchemistry Iceland |
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