Analysis of fluvial migration of the irish pollan Coregonus autumnalis, using Sr:Ca ratios of otolith

Abstract

The Irish pollan Coregonus autumnalis pollan (Pallas, 1776) is a unique and an endangered fish species endemic to the island of Ireland. However, there is little information available regarding the life history and migration of the species. The migratory history of the C. autumnalis pollan was examined for the first time in terms of strontium (Sr) and calcium (Ca) uptake in the otolith, by means of wavelength dispersive X-ray spectrometry on an electron microprobe. The Sr:Ca ratios measured along a transect from the core to the otolith edge showed consistently low Sr:Ca values, averaging from 1.0 × 10−3 to 1.4 × 10−3. The results suggested the non-anadromous (fluvial) life history styles of the Irish pollan C. autumnalis pollan, although the Arctic cisco C. autumnalis is typically an anadromous fish in low productivity river and coastal systems.