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¹ Instituto Tecnológico de Chascomús, INTECH (CONICET-UNSAM), Laboratorio de Ictiofisiología y Acuicultura, Avenida Intendente Marino Km 8.200 (B7130IWA), Chascomús, Buenos Aires, Argentina
² Instituto de Limnología “Dr. Raúl a. Ringuelet” ILPLA-(CONICET-UNLP), Boulevard 120, Casco Urbano, 1900 La Plata, Buenos Aires, Argentina
³ Dirección Provincial de Pesca. Ministerio de Agroindustria de la provincia de Buenos Aires DOI : 10.4194/1303-2712-v21_7_04 Viewed : 1602 - Downloaded : 1370 Cochicó belongs to `Encadenadas del Oeste` system of lakes being a typical water body of the Pampas region. The most abundant fish species in this lake is the pejerrey (Odontesthes bonariensis) valued due to the quality of its flesh and as a game fish. The aim of this study was to compare the gonadal stages of pejerrey during two consecutive spawning seasons (August to December) in relation to sexual steroids and temperature in this lake. In general, pejerrey gonadal development, the Gonadosomatic index and the plasma levels of estradiol and testosterone fluctuated in relation with temperature. In 2014 samplings, females started to ovulating in early August, with a peak during September-October and ending in December with many of them with atretic oocytes. However, in 2015, a marked delay in maturation was observed with ovulated fish only in October and December. This fact may be because the minors mean temperatures recorded in this year. For males, it was possible to find spermiating animals during the whole spawning season and only arrested animals in December. Unexpectedly, histological gonadal analysis revealed for the first time pejerrey with testis-ova, probably due to the intensive use of agrochemicals in this region. Keywords : Atherinopsidae, Climate, Pampas lakes, Reproduction, Sex hormones, Testis-ova