Application of genetic programming and River2D to assess the habitat preference of riverine fish: A case of Sicyopterus japonicus in Datuan stream

The river ecological conservation concept became important, the living right and diversity maintenance were main topics on river engineering and water resources development. The relationship between fishes and environmental factors had been quantified to assess the efficiency of the conservation projects. Some studies concluded that habitat suitability curves (HSC) can’t describe fish occurrence appropriately. This failure would be ascribed to non-linear and complex interactions between environmental factors affecting the habitat selection and to uncertainty in ecology. Therefore, it was important to find a new method to improved.
The study validated the HSC built by linear regression and genetic programming (GP) respectively, and then the accuracy of Sicyopterus Japonicus habitat preference in Datuan stream was predicted. Sensitivity analysis was applied for the relationship between the frequency of fish occurrence, current velocity and depth. River2D was considered as an efficient tool for simulating the flow condition of constant discharge here and then used to calculate the weighted usable area (WUA) for assessing the fish habitat distributions. Finally, discussed with flow conditions and compared the result with various of literatures.
The results showed that the best fish habitat condition described by the GP HSC and the traditional one were different. The traditional HSC was accurate and reliable to predict the frequency of occurrence of fish. Two type HSC reacted differently in sensitive analysis. In the best state, current velocity was so sensitive for traditional HSC as to be unsuitable for ecological engineering planning. For the result obtained from River2D, the WUA of downstream habitat from two type HSC were divergent. Furthermore, discussing with flow conditions and found out the results of GP habitat suitability curve were more in line with literatures.
This study showed up an improved method for the traditional fish habitat suitability estimation and also makes the prediction of Sicyopterus Japonicus more convincible. This confirms the fact that suitability could not be constructed through a linear process, which means the fish habitat preference could not be described through a simple linear trend. The nonlinear genetic programming could be a better tool for searching the relationship for suitability curve construction. All the consequences showd that the consideration for habitat factors frequency distribution was essential in a study of habitat suitability for fishes. This study aimed to apply the hydraulic simulation and habitat assessment measurement in reality and could provide information for ecological engineering design in the future.