Limnology and ichtyofauna of José María shallow lake (Córdoba, Argentina), with special focus on silverside (ODONTESTHES BONARIENSIS -VALENCIENNES, 1835-)

Abstract

In the southern region of Córdoba province there are many shallow lakes whose originsand salinity vary considerably. Most of these environments are used for recreational fishing of silverside (Odontesthes bonariensis). In this study, we characterize water quality and determine the diversity of zooplankton and ichthyofauna specially refering to O. bonariensis, in José María shallow lake (34º50'17''S, 63º37'23''W). This ecosystem is located in the basin of “Quinto” river (Córdoba, Argentina). Water quality variables were measured. Besides, water and zooplankton samples were taken to be analyzed in the laboratory. Fish were caught using different active and passive gears. The average values of pH, oxygen concentration, temperature, water transparency (Secchi disk) and depth were 8.51, 9.03 mg/L, 24.3 ºC, 44 cm and 1.99 m respectively. The shallow lake was classified as “turbid”. The water was oligohaline (4.09 g/L), sulfated sodium and very hard(484 ppm Ca CO3). A total of three crustacean and seven rotifer species were recorded. Metacyclops mendocinus(crustacean) and Brachionus plicatilis(rotifer) presented the highest densities (162 ind/L and 482 ind/L) respectively. A total of twelve species of fish, belonging to five orders and nine families, were captured (Shannon index = 2.23 bits). Odontesthes bonariensis was the most abundant species (50.8%) and, together with Cyphocharax vogaand Cyprinus carpio,they accounted for 85% of total biomass of fish caught. The population parameters of O. bonariensiswere: Weight= 0.0000047081*Lst3.178(R2=0.99, n=116); total length= 5.854+ Lst*1.168 (R2= 0.99, n= 117); Lst(t)= 489.02 (1-e-0.225(t-0.46)) and W(t)= 1647.5 (1-e-0.225(t-0.46))3.18.