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The bluemouth, Helicolenus dactylopterus, is a deep-sea scorpionfish widely distributed in the Atlantic Ocean and the Mediterranean. It is a common by-catch associated to many demersal fisheries. However, there is little information about the stock structure, stock dynamics and life history parameters of the bluemouth. From the perspective of stock identification, it is important to study growth in fish populations to better understand the possible morphological differences among populations and when and why do they arise. Thus, the aim of this study was to determine the growth (allometric) trajectories of shape for several bluemouth populations in Northeast Atlantic and Mediterranean using landmark-based geometric morphometric techniques. In this study, ontogenetic allometry was present in all of the bluemouth samples. Ontogenetic shape changes were most evident in the head and pectoral area, affecting the position of the snout, preopercular spines and pectoral fins, but changes in body depth and length were also important. However, the degree to which these ontogenetic shape changes were present in bluemouth from each of the studied areas was different, indicating that their growth trajectories are not homogeneous. The importance of this finding for size-correction of the shape variables in morphometric studies for stock identification is also discussed. [ABSTRACT FROM AUTHOR]

Abstract The bluemouth, Helicolenus dactylopterus (Delaroche 1809), is a marine demersal fish that is widely distributed in the Atlantic and the Mediterranean. It is targeted by longline fisheries around the Iberian Peninsula and it is a common by-catch associated with many demersal fisheries. However, limited information exists about the population structure in the NE Atlantic and Mediterranean. Thus, the bluemouth population structure in these regions was studied using a landmark-based geometric morphometric analysis. The purpose was to assess body shape variation among bluemouth and determine putative populations and their relationships. Three populations were identified in the western Mediterranean: two populations in the Alboran basin and another in the north-western basin (Balearic Sea and Catalonian coast). The population from the central Mediterranean did not seem to be effectively connected to the populations in the western Mediterranean. In the NE Atlantic, our results showed that at least four different bluemouth populations exist in the following areas: Galicia-Cantabrian Sea, Peniche (Portugal), the Gulf of Cadiz and the Porcupine Bank. A connection between bluemouth from the NE Atlantic and Mediterranean was observed, making unlikely that the Strait of Gibraltar acts as a barrier isolating Atlantic and Mediterranean bluemouth populations. The results of this study provide evidence that different bluemouth populations exist, which is relevant for stock assessment and management of this species. [ABSTRACT FROM AUTHOR]