Sex identification of animal species is a critical piece of information to derive parameters for population
dynamic models. In the context of stock assessment (SA) for marine population, sex identification
provides information about the sex-ratio of the population which is subsequently used to calculate the
stock spawning biomass. In these SA models, sex-ratio can be set to an constant value throughout the
lives of individuals (e.g. 0.5) or age-structured to account for changes linked to the physiology of
individuals (e.g. females may live longer and represent a larger proportion of the population) or the
selectivity of the fishery (e.g. a gender may be more accessible to the fishery at specific stages). The
most common methods to identify sex are derived from direct observation of gonads. However,
scientists must access the whole fish, which is rarely the case for large pelagic species in the IOTC fishery
as fish that are landed have been gutted. Here we show the preliminary results of sex identification of
swordfish (Xiphias gladius) using a genetic method: Amplified Fragment Length Polymorphism (AFLP).
This polymerase chain reaction (PCR)-based genetic tool is a highly sensitive method for detecting
polymorphisms in DNA. We tested the hypothesis that male and female swordfish present a genetic
polymorphism linked to sex. Using a multiplexing technique (i.e. a combination of different restriction
enzymes and PCR primers), we identified potential locations in the swordfish genome where
polymorphism could occur. Comparing results between 3 males and 3 females of swordfish, we were
able to identify 3 couples of restriction enzymes and primers over 64 combinations that led to potential
sex-specific polymorphism identification. Higher sampling (40 males and 40 females) will be performed
to confirm these results. This method has the advantage of being low cost (XX$ per sample), simple to
develop, requires few genetic laboratory analysis or preparation (DNA extraction, PCR,electrophoresis
and a capillary sequencer for DNA fragment analysis) and the genetic material required is minimal and
can be taken from a living or dead animal.