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Research article2020Peer reviewedOpen access

Prevalence of stocked whitefish in River Kemijoki, Finland, inferred by micro X-ray fluorescence analysis of otoliths

Finnas, Viktor; Lill, Jan-Olof; Heimbrand, Yvette; Blass, Martina; Saarinen, Timo; Lahaye, Yann; Jokikokko, Erkki; Hagerstrand, Henry

Abstract

Micro X-ray fluorescence (mu-XRF) analysis of otoliths was evaluated as a method to estimate the proportion of stocked one-summer-old whitefish Coregonus lavaretus L. in catches of adult fish (n = 20) ascending the River Kemijoki to spawn. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis was applied as control. Polished otoliths were scanned with mu-XRF to obtain strontium maps that were used to infer visually the provenance of the whitefish. Thirteen of the fish showed signs of being stocked as one-summer-old fingerlings. LA-ICP-MS was applied to determine the elemental composition in a spot outside the core of the otolith. The results were largely consistent with the visual inspection of the mu-XRF mapped otoliths. In conclusion, mu-XRF mapping successfully identified whitefish stocked as one-summer-old fingerlings. The vast majority of whitefish returning to the River Kemijoki to spawn were stocked fish.

Keywords

mu-XRF; Baltic Sea; elemental analysis; LA-ICP-MS; otolith; whitefish

Published in

Fisheries Management and Ecology
2020, Volume: 27, number: 5, pages: 490-497 Publisher: WILEY