Potential distribution of endangered Mexican golden trout (Oncorhynchus chrysogaster) in the Rio Sinaloa and Rio Culiacan basins (Sierra Madre Occidental) based on landscape characterization and species distribution models

The Mexican Golden Trout (Oncorhynchus chrysogaster) is a threatened native species inhabiting three river basins in the Sierra Madre Occidental. Despite some efforts from science groups to obtain information about this trout, the Rio Sinaloa and Rio Culiacan basins, to the south, remain the least studied area, compared to the Rio Fuerte basin. To overcome this gap, a survey (2014 to 2015) was undertaken to obtain new records and confirm the presence for historic records in both watersheds. After filtering records for this species, eighteen locations were used to model potential distribution, using the GARP and MaxEnt, including landscape characterization based on hydrologic analysis and satellite imagery classification. Coincidence between models was >85% for a potential distribution area of 4300 km(2), defined by six bioclimatic and physiographic variables, with the hydrologic network covering 3000 km. To avoid overestimation, the final distribution area included only the 100 m fringe surrounding the drainage network and its associated landscape features. Jackknife resampling was used to validate both the models, successfully predicting more than 80% of the locations (p < 0.001). The estimated area covers 275 km2, mainly defined by second- and third-order streams, at altitudes >2000 m, high water quality (transparent, dissolved oxygen >5 mg L-1; temperature < 26 degrees C), and was part of amatrix of undisturbed forests. This study provides new findings about this endangered species and new elements for designing appropriate monitoring programs supporting trout conservation and management.