Elemental composition of illicia and otoliths and their potential application to age validation in white anglerfish (Lophius piscatorius linnaeus, 1758)

Deirdre Brophy,Maria Ching Villanueva,Beatriz Morales-Nin,Sílvia Pérez-Mayol,Hans D Gerritsen,Roxanne Duncan,Karin Hüssy,Audrey J Geffen

doi:10.1016/j.ecss.2021.107557

Abstract

The incorporation of trace elements into the calcified structures of fish can vary seasonally. Interpretation of these seasonal signals can provide information about fish age. This approach offers great promise for objectively estimating age and corroborating other methods of age estimation for fish stock assessment. This study investigated seasonal variation in trace element composition of otoliths and illicia from white anglerfish (Lophius piscatorius L.), a species that is very difficult to age using visual interpretation of growth bands in their calcified structures. A suite of trace elements (Na, Mg, Zn, Sr, Ba in illicia and Na, Mg, K, Sr, Ba in otoliths) was measured with LA-ICPMS using discrete ablations and continuous line scans. A method is presented to obtain reliable measurements of microchemical composition from illicia. Variation in elemental concentrations at the edge of the illicium was primarily related to fish length and no differences were detected between fish collected at different times of the year. In otoliths, Sr concentrations at the edge (0–100 μm) were highest in anglerfish collected during wintertime (quarter 1). Seasonal differences in Sr were statistically significant but small; a larger proportion of the explained variance was attributed to length and individual variability. Nonetheless, the seasonal pattern was consistently detected across all size classes, indicating that the analysis of cycles in otolith Sr could potentially provide a tool to support age estimation in white anglerfish.

Highlights

A robust understanding of life history strategies and growth dy namics supports the effective management of fishes in marine, coastal and freshwater systems worldwide
Trace element concentrations in calcified structures often vary across life history transects due to fluctuations in metabolism or environmental conditions (Kalish, 1991; Morales-Nin et al, 2012)
This study investigated trace element concentrations at the edge of white anglerfish otoliths and illicia as an important first step in the development of microchemistry-based age determination methods for the species

Summary

Introduction

A robust understanding of life history strategies and growth dy namics supports the effective management of fishes in marine, coastal and freshwater systems worldwide Calcified structures such as otoliths, bones and scales, register the individual history of each fish, with the daily and seasonal growth patterns recorded in the structure of the organic and inorganic matrix as visual growth marks. Clearly defined minima and maxima in the concentrations of some ele ments and isotopes have been shown to correspond to age (Heimbrand et al, 2020; Hüssy et al, 2015; Kastelle et al, 2017; Siskey et al, 2016) These patterns provide a tool to validate the periodicity of growth marks in calcified structures. The approach is useful for stocks without clearly defined, annually recurring growth marks in their calcified structures, an issue that can hamper age estimation and age-based assessment and challenge the implementation of Maximum Sustainable Yield (MSY)-based management, as is required under the common fisheries policy (CFP) (Maunder and Piner, 2014)

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