Intraspecific variability in otoliths of Helicolenus dactylopterus from the NE Atlantic and Mediterranean Sea

Abstract

Accurate population identification is essential for effective fisheries management, providing a foundation for models assessing population health and sustainability. This study explores phenotypic plasticity in the otolith contour shapes of blackbelly rosefish (Helicolenus dactylopterus), a species with a poorly understood population structure despite its vulnerability to overfishing. A total of 391 otoliths were analyzed from five regions (mainland Portugal, the Canary Islands, Mauritania, Morocco and the Catalan coast in the northwestern Mediterranean) using wavelet functions, revealing significant regional differentiation, with classification rates above 94%. Two distinct clusters emerged, clearly separation African from European populations. Shape variability was most pronounced in the anterior region, height and posterior ventral margin, with morphotypes distributed unevenly across regions. In particular, European populations showed thinner and more elongated otoliths, while African populations exhibited wider and more elliptical shapes. These findings highlight the critical role of phenotypic diversity in fisheries management, underscoring how phenotypic plasticity shapes population structure and enables geographic expansion in response to environmental gradients. Integrating phenotypic variation into assessments will enhance sustainable management of blackbelly rosefish populations.