Biology of silverside Odontesthes bonariensis (Pisces, Atherinopsidae) in the shallow lake “Los Charos” (Córdoba, Argentina)

Abstract

The silverside Odontesthes bonariensis is the most important species in the fisheries of central Argentina. Capture per unit effort (CPUE), body condition, growth and feeding were studied for O. bonariensis in the Pampean shallow lake “Los Charos” (34º28´S, 64º23´W, 240 ha), located in Córdoba province. Four seasonal sampling procedures were carried out during 2002-2003. Floating gillnets and trawlnets were used to capture the fishes. Specimens captured (n= 2862) were ranged between 38 and 380 mm of standar length (StL). CPUE average was 74.3(±71,0) kg/20 hs/gillnets. The StL–weight relationship showed signifficant differences along the seasons (P< 0,01). The body score indices were within the reffered limits for this species. Growth was calculated by StL(t)= 459,8*[1–exp(-0,3105*(t-0,175))]. The StL–Total length (TL) ratio was TL(mm)= 8,23+StL*1,14 (n= 283; R2= 0,99). For the young fishes the zooplankton constituted a secundary feeding source. In individuals older than 3 years of age, a marked canibalism was observed, which might explain partially their body condition. The shallow lake “Los Charos” shows an elevated production of O. bonariensis.