Determination of Habitat Preference Curves of Cryphiops caementarius in the Rio Tambo, Arequipa, Perú

Abstract:

In water-scarce regions, competing water demands and multiple withdrawals can put additional stress on aquatic communities in rivers. One common method for minimizing these impacts is to calculate ecological flow requirements, which requires knowing both river bathymetry and the habitat preference curve of an indicator species. In the case of the coastal rivers of southern Peru, the river shrimp Cryphiops caementarius is not only ecologically important, but also holds economic and social value. Thus, C. caementarius was used to determine the habitat preference index and subsequently build habitat preference curves for the Tambo River, in the Arequipa Department of Southern Peru. To create habitat use indices, 1810 individuals of C. caementarius were captured, and depth, total stream velocity, focal velocity, and type of substrate were determined at capture points. In the same river reach, cross-sectional measurements were recorded at 45 representative transects (including riffles, runs, pools, etc), and total velocity and substrate were measured at a total of 349 points in these transects. These values were compiled to determine the habitat availability index. A relationship was created between these two indices (use index / availability index) to create the habitat preference index, which was in turn used to construct preference curves. Results show that C. caementarius individuals most frequently prefer depths between 0.20 and 0.40 m and a substrate of "cobbles" (between 64- 256 mm). The highest frequency of total velocity preference was observed at 0.11 m/s, though a uniform preference distribution was observed between 0.4 and 1.5 m/s. These results can be used to inform ecological flow requirements and water withdrawal limitations, as well as to protect a species of social and economic significance in Arequipa, Peru.