Modelling habitat requirements of Alburnus atropatena in the Jajroud protected River

Finding habitat requirements for fish in fluvial water ecosystems is a key factor in conservation and decision making for their management, which unfortunately does not have enough scientific information in this field. The purpose of this study is to identify the optimal range of habitat variables for Alburnus atropatenae in the Jajroud protected river and compare different composite approaches in the modeling of this species.

In this study, the habitat of A. atropatenae sampled in the form of 71 points in the Jajroud river. Physical variables of habitat measured including depth, water velocity and substrate type. After sampling the fish by electrofishing, the total length of the fish measured. Habitat suitability curves developed by univariate method then combined habitat suitability calculated by multiplication, minimum, arithmetic mean and geometric mean methods. To validate the results, two statistical metrics of mean absolute error (MAE) and root mean square error (RMSE) used.

Overall, 235 individual of A. atropatenae caught including 221 adults and 14 juveniles whose total body length varied from 23 mm to 148 mm. Physical habitat variables included a depth of 6-56 cm, a flow velocity of 4-29 cm / s, and a riverbed with a particle size of "very fine gravel" to "small cobble". The preferred and optimal range habitat for this species included a depth of 16-25 cm, a flow velocity of 5-10 cm / s and a bed with small cobble structure. Among univariate models, the riverbed-based model had the lowest error. Among the models of combined habitat suitability, multiplication method had the lowest values ​​of MAE and RMSE measures, and was low-error model. The arithmetic mean method had the highest values ​​of these measures and had detected as the high-error model.

This is the first study related to the ecology of A. atropatenae in Iran, which has identified the optimal habitat of this species. The variable of bed structure is determinative more than two variables of depth and flow velocity in habitat selection by this species. Also in combined habitat suitability modeling, the multiplication method has priority and importance.