GENETIC POPULATION STRUCTURE OF ATLANTIC SWORDFISH: CURRENT STATUS AND FUTURE DIRECTIONS

• Main Authors: J. R. Alvarado Bremer, J. Mejuto, J. Gómez-márquez, C. Pla-zanuy, J. Viñas, C. Marques, F. Hazín, M. Griffiths, B. Ely, B. García-cortés, T. W. Greig
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Indian; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.572.2966; http://www.iccat.int/Documents/CVSP/CV061_2007/no_1/cv061010107.pdf

The genetic population structure of Atlantic swordfish has been studied with mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) data using a variety of laboratory methodologies and analytical approaches. In here, we compare preliminary data for the nuclear genes ldhA and Calmodulin (Cam) from the South Atlantic against published data from other regions. Results from Cam, but not ldhA, confirm the partitioning of NW Atlantic and South Atlantic swordfish populations. The distribution Cam alleles and CR-I haplotypes is homogeneous throughout the entire South Atlantic (South of 5°N) and comparisons with the Indian Ocean confirm the genetic differentiation of these two basins. However, the boundary that separates the North Atlantic from the South Atlantic cannot be delineated with the present data, and additional temporal-spatial sampling is necessary to resolve this issue. It is important to note that the North Atlantic has been characterized primarily using NW Atlantic and Caribbean samples, with very limited sampling coverage of the NE Atlantic. However, because mixing with the Mediterranean swordfish may occur in the NE Atlantic, it is important to delineate the area of contact between these two regions prior to comparing NE and NW Atlantic samples. Using CR-I data, we show that the mixing zone of NE Atlantic and the Mediterranean is restricted to a small zone west of Gibraltar that extends west to 10°W. Future studies of population structure in the North Atlantic should consider this evidence to avoid Type I errors. This paper also underlines other areas of research necessary to clarify the entire population structure of Atlantic swordfish.