Geographic variation and juvenile migration in Atlantic redfish inferred from otolith microchemistry

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Abstract
Golden redfish (Sebastes marinus) and deep-sea redfish (S. mentella) are heavily exploited fish resources in the North Atlantic, but their stock delineation remains unresolved. The present study examined the use of otolith microchemistry as a stock separation tool for redfish. By determining minor and trace elements in redfish otoliths from various areas in the North Atlantic, geographic and temporal variations in otolith microchemistry were investigated. Relatively high temporal stability in otolith elemental composition was found for juvenile redfish from nursery areas off East Greenland. Elemental concentrations in the nucleus, juvenile and marginal otolith zones differed significantly between areas and showed consistent longitudinal trends for some elements. Multivariate analysis of element constituents by area, however, revealed poor geographic separation (< 50% cross-validated classification) for both species. Otoliths of juvenile S. mentella from demersal nursery grounds and adjacent pelagic habitats showed no significant differences between areas. The results are in accordance with the recently observed low morphometric and genetic heterogeneity of redfish across the North Atlantic. It is, however, unclear if the lack of clear spatial separation by natal signatures is due to a common origin of the investigated fish or due to limited variability of the chemical composition of their ambient environment.

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