Population structure of Chelidonichthys lucerna in Portugal mainland using otolith shape and elemental signatures

The tub gurnard, Chelidonichthys lucerna, is considered the most important commercial fish species of the family Triglidae captured by the Portuguese traditional fisheries. However, the data available about its population structure, movement patterns and habitat connectivity is, at present, scarce. In this study, otolith chemistry and shape analyses of 90 individuals captured, between March and June 2016, in the three main fishing grounds of the Portuguese mainland coast (Matosinhos, Aveiro and Peniche) were investigated. Otolith morphological (shape indices and elliptic Fourier descriptors) and elemental (Ba:Ca, Fe:Ca, Mg:Ca, Mn:Ca, Sr:Ca and Zn:Ca) signatures of individuals with similar length range were assessed through uni and multivariate statistical tests. The overall combination of otolith elemental chemistry and morphology techniques revealed the highest re-classification success (74%) of samples to their original location and the existence of significant differences among sampling regions. However, linear discrimination function analyses and canonical analyses of principal coordinates did not fully discriminate C. lucerna individuals from the three sampling regions of Portugal. Moreover, the hereby data revealed a partial overlap among individuals from the different sampling regions. The obtained shape and chemical signatures suggest that C. lucerna is apparently a unique, although not necessarily homogenous, single population-unit in Portugal mainland, and that these fish populations should not be managed separately for fisheries purposes.