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AB 2:171-178 (2008)  -  DOI:

Prevalence and intensity of occurrence of vaterite inclusions in aragonite otoliths of American eels Anguilla rostrata

B. M. Jessop1,*, J. C. Shiao2, Y. Iizuka3, W. N. Tzeng4,5

1Department of Fisheries and Oceans, Bedford Institute of Oceanography, PO Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada
2Institute of Oceanography, 4Department of Life Science and 5Institute of Fisheries Sciences, College of Science, National Taiwan University, Taipei, Taiwan 10617, ROC
3Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, Taiwan 11529, ROC

ABSTRACT: The presence of vaterite mosaic in the aragonite otoliths of anguillid eel otoliths is readily determined by reflected light microscopy after etching with EDTA. The prevalence and intensity of vaterite inclusions in sagittal otoliths of 165 American eels Anguilla rostrata were examined in relation to latitude and migratory history. Prevalence varied significantly (range: 21.3 to 58.8%) among 3 rivers in Atlantic Canada and increased non-linearly with latitude. Habitat differences among sites may confound the relation because most (48%) vateritic otoliths came from eels with a history of estuarine residence and inter-habitat migration. The limited number of sites, restricted geographic range and modest otolith sample sizes makes premature any conclusion that the prevalence of vateritic otoliths in American eels increases with latitude. The frequency of vaterite inclusions in otoliths (n = 63) was low (1 to 6) and did not vary among sites. Vaterite intensity was low (<5%, median = 0.21%, over all sites after excluding 7 outliers [11.1% of vaterite group] ranging to 37% vaterite content). Mean intensity varied significantly among sites, but the means are trivially low and of no practical consequence. Mean Sr:Ca concentration ratios were much lower (10 to 17%) in vaterite than in aragonite, leading to possible misidentification of habitat residence and migratory history, particularly for eels resident in saline waters. The presence of vaterite in anguillid eel otoliths is not an impediment to the use of microchemical analysis methods provided that vaterite inclusions are identified and avoided so as to prevent potentially serious misidentification of habitat residence and inter-habitat migratory history.

KEY WORDS: American eel · Otoliths · Vaterite · Prevalence · Intensity

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Cite this article as: Jessop BM, Shiao JC, Iizuka Y, Tzeng WN (2008) Prevalence and intensity of occurrence of vaterite inclusions in aragonite otoliths of American eels Anguilla rostrata. Aquat Biol 2:171-178.

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