L. C. Gomes and L. E. Miranda, Mississippi Cooperative
Fish and Wildlife Research Unit, P.O. Box 9691, Mississippi State, Mississippi 39762;
Voice 601-325-3217; FAX 601-325-8726; E-Mail smiranda@cfr.msstate.edu
or lgomes@magnolia.cfr.msstate.edu
Keywords: reservoirs, South America, primary production,
chlorophyll-a, hydrology
Fishery yields in reservoirs of the Upper Paraná River are generally
low relative to other South American basins or those in other continents. However,
artisanal and commercial fisheries in these reservoirs are very important for local
inhabitants, as a source of food and income. The objective of this study was to
investigate if primary production is a factor limiting fishery yield in reservoirs of the
Upper Parana River, and to identify abiotic conditions potentially stifling primary
production. We used a comparative approach wherein various characteristics of 13
reservoirs in the Upper Parana River were compared statistically against 58 reservoirs in
the south-central United States. Fishery yield in the 71 study reservoirs was
directly related to chlorophyll-a (r2 = 0.50), and the relation was consistent
between Upper Parana River and south-central U.S. reservoirs. In turn, chlorophyll-a was
directly related to phosphorus levels, retention time, and reservoir volume, but the
relation differed between data sets (R2 = 0.75). Reservoirs in the Upper Parana
River had nutrient concentrations similar or higher than U.S. reservoirs, but lower
retention time and larger volume leading to reduced in-reservoir primary production and
fishery yield. This is the first time limited fishery yield in the Upper Parana River is
shown to be linked to low primary productivity and reservoir hydrological characteristics.
