Population structure of Atlantic swordfish (Xiphias gladius L. 1758) (Teleostea, Xiphiidae) using mitochondrial DNA analysis: implications for fisheries management

Abstract

Recent studies on Atlantic swordfish (Xiphias gladius L. 1758) genetic structure have demonstrated significant heterogeneity but the precise boundary between populations remains to be identified. In this context, genetic diversity was investigated by PCR–RFLP analysis at the control region of mitochondrial DNA (D–loop) from 274 swordfish specimens collected from five different areas of the Atlantic Ocean. The analysis of molecular variance (AMOVA) showed that genetic variation was mainly due to differences within rather than between the studied areas. Additionally, the phylogenetic analysis did not show evident relationships among haplotypes from all areas. However, low but significant FST values were recorded when comparing Equatorial samples with those from the north central and north tropical Atlantic. These results do not support a need for changing the current management boundary for the Atlantic fishery. Key words: Xiphiidae, Swordfish, Xiphias gladius, Mitochondrial DNA, Genetic variability, Atlantic Ocean.Estudios recientes sobre la estructura genética del pez espada del Atlántico (Xiphias gladius L. 1758) han demostrado una heterogeneidad significativa, pero los límites precisos entre poblaciones no han sido identificados. En este contexto, la diversidad genética se ha investigado mediante análisis PCR–RFLP en la región control de ADN mitocondrial (bucle D) de 274 peces espada recolectados en cinco zonas diferentes del océano Atlántico. El análisis de la varianza molecular (AMOVA) mostró que la variación genética se debía a diferencias en cada zona y no entre las zonas estudiadas. Además, los análisis filogenéticos no muestran relaciones evidentes entre los haplotipos de todas las zonas. A pesar de ello, al comparar las muestras ecuatoriales con las de zonas más al norte, se obtienen valores de FST bajos pero significativos. Estos resultados indican que no es necesario cambiar los límites de las zonas de gestión para la pesquería del Atlántico. Palabras clave: Xiphiidae, Pez espada, Xiphias gladius, ADN mitocondrial, Variabilidad genética, Océano Atlántico.Recent studies on Atlantic swordfish (Xiphias gladius L. 1758) genetic structure have demonstrated significant heterogeneity but the precise boundary between populations remains to be identified. In this context, genetic diversity was investigated by PCR–RFLP analysis at the control region of mitochondrial DNA (D–loop) from 274 swordfish specimens collected from five different areas of the Atlantic Ocean. The analysis of molecular variance (AMOVA) showed that genetic variation was mainly due to differences within rather than between the studied areas. Additionally, the phylogenetic analysis did not show evident relationships among haplotypes from all areas. However, low but significant FST values were recorded when comparing Equatorial samples with those from the north central and north tropical Atlantic. These results do not support a need for changing the current management boundary for the Atlantic fishery. Key words: Xiphiidae, Swordfish, Xiphias gladius, Mitochondrial DNA, Genetic variability, Atlantic Ocea