Trace metals in four structures of fish and their use for estimates of stock structure

Abstract

Trace elements in calcified tissues have been suggested as one of the most powerful means for stock discrimination yet developed. The structure of choice for determining elemental composition or fingerprints is the otolith, although other structures also incorporate trace elements into their matrix. The aim of this study was to compare the elemental fingerprints of four structures (otoliths, scales, eye lenses, and spines) of a territorial reef fish to determine whether there were correlations between otoliths and each of the other structures. Elemental fingerprints of juvenile ([is less than] 3 years of age) and adult fish (which may reach a maximum age of 37 years) were also compared for each structure to determine whether there may be differences between size classes of fish. All structures were analyzed by solution-based inductively coupled plasma-mass spectrometry (ICP-MS). Otoliths, scales, spines, and eye lenses differed in composition. Calcium dominated otoliths, scales, and spines but was not detected in eye lenses. Some elements, for example barium, showed significant correlations between the otolith data and that of scales and spines of both juvenile and adult fish. A multivariate test of matrix correspondence (Mantel's test) detected significant relationships between the otolith data and the data matrices for each of scales and spines of both juvenile and adult fish. Significant relationships between the otolith data and the eye lens data were detected only for juvenile fish. Significant differences were also found between juvenile and adult fish for all structures. The BIOENV multivariate analyses showed that the highest rank correlation was found between the otolith data and the scale or spine data for both juvenile and adult fish. These data suggest that the use of scales and spines may provide a nonlethal alternative to the use of otoliths for future stock discrimination studies.