Evaluation of some growth and geometric morpometric parameters of endemic pseudophoxinus antalyae (Teleostei: Leuciscidae) Bogutskaya, 1992 populations in the Düden stream basin

Organisms with particularly wide ranges of distribution, such as fish, often exhibit local ecological specializations based on resource and habitat use. Therefore, the body morphology of populations living in different environmental conditions (or different habitat types) can differ significantly. Besides, large dams with reservoirs may cause different selections in fish morphology; however, the impact of the isolation caused by hydroelectric power plants (HPP) and waterfalls is largely unknown. The Düden Stream basin, where this study was conducted, has been under threat for a long time due to intense anthropogenic pressures (domestic and industrial wastes, agricultural activities, 2 HPP, non-native fish introduction, etc.). Düden Stream is home to an endemic and threatened fish species, Pseudophoxinus antalyae Bogutskaya, 1992 (Cypriniformes: Leuciscidae). It is aimed to evaluate the population status and body morphology of P. antalyae depending on habitat types and isolation in an ecosystem under such intense anthropogenic pressure. In this study, which was prepared in this direction, the life history characteristics of P. antalyae subpopulations i) through population demographics, and ii) to identify patterns of morphological variation (body size and shape). For this purpose, population abundance, biomass and condition, and length-weight relationships were calculated to compare the population characteristics of a total of 172 individuals caught from three sites (Kaynak, upper and lower Düden) along the Kırkgöz Spring-Düden Stream basin. In addition, 13 landmarks were created on a total of 120 individuals, and variations in body shape were evaluated by geometric morphometry analysis. Some univariate (ANOVA) and multivariate statistical analyzes (MANOVA, PCA, and DFA) were used to reveal shape differences/similarities between populations depending on habitat type and isolation. The abundance and biomass of the Kaynak population were found to be significantly higher than the other two populations. Condition values of the populations also differed significantly from each other in all three locations. It was determined that the Kaynak and Lower Düden populations showed positive allometric growth, whereas the individuals belonging to the Upper Düden population showed negative allometric growth. ANOVA results revealed that body size (centroid size) varied significantly depending on locations. While the individuals in the Kaynak population have the largest body, the Lower Düden population has the smallest body. Multivariate statistical analysis results revealed significant morphological differences in body shape among the subpopulation of P. antalyae along the Düden Stream. Especially between the lentic and lotic populations, the shape differences arising from the habitat type and the isolation caused by the HPP and waterfall are quite evident. As a result, differences in body shape, especially among interconnected populations, can be explained by phenotypic flexibility, the variation in body shape resulting from isolation caused by HPP and waterfall may arise from genetic differentiation, phenotypic flexibility, or a combination of both.