Otolith geochemistry indicates life-long spatial population structuring in a deep-sea fish, Coryphaenoides rupestris

Abstract

Little is understood about connectivity of deep-sea fish populations. Analysis of the geo- chemical properties of fish otoliths is one way to draw inferences regarding their movements and habitat use in the marine environment. Trace element and stable isotope analyses of otoliths were undertaken to assess patterns of spatial and temporal population structure of a wide-ranging deep- water fish, the roundnose grenadier Coryphaenoides rupestris. Fish were sampled from 4 locations across the distribution range of the species in the northeast Atlantic. Multivariate analyses of elemen- tal ratios (Li/Ca, Mn/Ca, Ba/Ca, Zn/Ca, Cu/Ca) revealed strong geographic separation at each life stage, and an overall significant difference between life stages. Otolith oxygen (δ 18 O) and carbon (δ 13 C) stable isotope analysis indicated a depth migration (and reduction in metabolic activity) from relatively shallow in the juvenile phase to much deeper in the adult phase at all locations. The results suggest that roundnose grenadier are comprised of geographically distinct population units that persist throughout their life-history, migrating deeper as they get older.