Abstract

Colombia is home to a rich diversity of freshwater species, including Schizodon fasciatus, an important fish in the Catatumbo sub-basin that serves as a critical resource for local food security. However, agricultural activities and ecosystem alterations threaten its populations. This study examines the morphological variability of S. fasciatus from two tributaries of the Catatumbo sub-basin, the Grita and El Zulia rivers, using geometric morphometrics to assess how habitat conditions influence body shape. The results showed significant shape variation between populations. Specimens from Puerto Santander (Grita River) revealed longer pectoral fins, while those from El Zulia showed more compact bodies. These differences were influenced by environmental parameters such as conductivity, pH, salinity, temperature, and dissolved oxygen. The Grita River, with better-conserved riparian zones, provided conditions supporting more hydrodynamically adapted shapes, whereas the El Zulia River, heavily impacted by deforestation and agricultural runoff, was associated with compact body shapes and higher phenotypic variability. This research highlights the importance of habitat quality in shaping the morphology of S. fasciatus. By linking environmental stressors to morphological adaptations, the findings contribute to understanding the ecomorphological behavior of S. fasciatus, providing a foundation for its conservation and sustainable management in the Catatumbo sub-basin.