Danilo Araujo Soares Pereira

This study aimed to identify geographical distribution patterns of the giant short‐tailed river stingray Potamotrygon brachyura and the motoro stingray Potamotrygon motoro in the Uruguay River basin. Data on presence/absence of stingrays were based on fishers' knowledge accessed by interviews through expeditions in Brazil, Argentina and Uruguay. The significance in independent variables (environmental descriptors) of elevation ( p = 0.00 for both species), upstream distance ( p = 0.02 for P. brachyura and 0.03 for P. motoro ) and downstream distance ( p = 0.00 for both species) explained the presence of stingrays in the main water bodies of lower Uruguay and their absence throughout upper Uruguay more than the biogeographical barrier of the Salto de Yucumã ( p = 0.99 for both species) and basin area ( p = 0.42 for P. brachyura and p = 0.43 for P. motoro ) in the last steps. The construction of logistic models also provided high sensitivity (96.3%–97.5% for P. brachyura and 62.3%–71.7% for P. motoro ) and specificity (86.8% for P. brachyura and 85.4%–86.5% for P. motoro ) results between observed and presumed distribution for both species, with values of false positive and false negative varying between 1.3%–14.1% and 6.4%–9.2%, respectively. Further studies are still necessary not only in the Uruguay River basin or the La Plata basin complex, but for all South America, considering potential changes in the state of knowledge of freshwater biodiversity and its geographical distribution, including the possibility of undescribed species.

The L46 (Hypancistrus zebra) stands out as one of the most valuable Amazonian species in the international market for ornamental fish and faces a notable problem: the risk of extinction versus the demand for new specimens for aquariums. Considering that breeding in captivity can be a conservational tool for aquatic species and an alternative source for generating income, the objective of the present paper was to verify the economic feasibility of producing H. zebra in recirculation aquaculture systems (RAS), in different scenarios of rearing: residential breeding (S1), mid-size store production (S2) and large-scale production as a supplier (S3). The main profitability indicators used were: net present value (NPV), internal rate of return (IRR) and payback period (PP). The selling price per unit was fixed in US$260.15 (S1/S2) and US$156.09 (S3). The largest investments were made with the acquisition of broodstocks (S1/S2) and property (S3), while the highest costs were with labor (S2/S3) and taxes (S1). Only S1 demonstrated economic profitability (NPV 8.50% = US$28,187.85; IRR = 74.71%; PP = 1.80 years). Conclusion: the production in this study appeared to be profitable on smaller scales, however the profitability of large-scale production depends upon reducing expenses and increasing the selling price.