Molecular identification and biometric analysis of Macaronesian archipelago stocks of Beryx splendens

Abstract

The genetic variability shown by geographically distant populations of the alfonsino Beryx splendens off the Macaronesian archipelagos (the Canary Islands, Madeira and the Azores) was surveyed by examining polymorphisms in three mitochondrial DNA regions (cytochrome b, rRNA 16S and control region). Particular DNA polymorphisms were detected in fish specimens from the three archipelagos. Two single nucleotide substitutions in the rRNA 16S region and one in the control region served to identify the Azorean populations, while one cytochrome b substitution was sufficient to discriminate specimens fished off the coast of Madeira. Specimens from the Canary Islands could be identified by a distinct Sau3AI restriction enzyme pattern found in the mitochondrial control region. To test the congruence of these molecular observations with the morphological and meristic discriminatory analyses generally used in fisheries research, a pilot study was conducted to distinguish between two of our sampling areas: Canaries and Madeira. Analyses based on both morphometric and meristic data were more reliable than those based solely on morphometric data. The discriminating factors identified were cephalic length and number of soft rays in the anal fin. The proportions of specimens correctly classified were in the range 67.2–70.7%. Although previous hypotheses suggest genetic homogeneity at the inter-oceanic scale consistent with the long pelagic stage of marine species, discriminatory haplotypes were detected according to the three mitochondrial gene fragments despite the relative geographical closeness of the Macaronesian archipelagos (Canaries, Madeira and Azores). These geographical differences were also supported by biometric data. Discrimination among populations of the three archipelagos suggests limited genetic flow between them, such that they should really be considered as independent stocks for fisheries.