Your place, my place…, distribution of Agonostomus monticola and Sicydium multipunctatum in the Acahuapa Watershed

Abstract

Diadromous fish undergo habitat shifts over their life cycles, dwelling between different environments. In the Acahuapa River watershed, the distribution, abundance, and length structure of A. monticola and S. multipunctatum were assessed in its tributary rivers and main channel for 1 year. Fishes were captured using electrofishing devices and nets. Environmental variables, habitat traits, and land use around the sampling points were taken into consideration. A total of 222 A. monticola and 183 S. multipunctatum were recorded during the sampled year. Their distribution was restricted to 8 of the 17 sampling points. Both species co-occurred at 7 of 8 sites, all at elevations between 19 and 325 m asl. Both species were more abundant in lower parts of the watershed and in the tributary rivers than in the main channel. Water temperature, dissolved oxygen, river width and depth, current speed, substrata dominated by rocks and logs, and surroundings of forest and small-scale agriculture favor the presence of these fishes. The smaller individuals of A. monticola occurred at lower elevations of the watershed but fish length differences were not present at the main channel or at the tributaries. For S. multipunctatum, the larger fish were captured also at low elevations and at the main channel of the Acahuapa River watershed.