Intraspecific Meristic Variation in <i>Gambusia holbrooki</i> from the Middle East and its Implications for Stock Structure and Taxonomic Status

An analysis was conducted on the variation in the counts of seven meristic traits of the eastern mosquito fish, Gambusia holbrooki, using samples collected from ten different sites in the Middle East. These sites are located along the Tigris, Euphrates, and Shatt al-Arab Rivers, spanning across Iraq, Iran,Türkiye, and Syria. The study revealed a northward increase in the average values of these meristic traits, with the highest recorded in Türkiye and the lowest in the southern region of Iraq. The statistical analysis using Boxplots demonstrated that the seven meristic features were distinct across different rivers, with no overlap observed. Furthermore, the meristic counts of the sexes were not substantially different (p ≥ 0.05). Analysis of each meristic trait variable suggested that the variations between samples were likely affected by several surrounding variables, such as ambient temperature, nutrient availability, currents, and genetic isolation patterns in the studied Middle East region. On the other hand, the study discussed the potential for implementing G. holbrooki stock identification.