Extensive cage culture of pejerrey (Odontesthes bonariensis) in a shallow pampean lake in Argentina

AbstractPejerreyisanimportantzooplanktivorousnative¢shof theArgentinean inland waters. It has been tradi-tionally propagated for stocking purposes by rela-tively costly semi-intensive and intensive methods.Inthis study, we evaluated the implementationof anextensiveculturemethodbyusing£oatingcagesinashallow pampean lake. Four cages were installed inthe Lacombe Lake and stocked with juveniles(16.24 1.69mmlength)at50¢shm 3 density forgrowing until the size of 150mm, which is consid-ered as a suitable size for stocking. Throughout theexperiment, thetemperaturerangedbetween10 and26 1C and the zooplankton biomass ranged between12 and 3269 mgdwL 1 . The growth patterns in thelengthwere similar inthefourcages anddirectly re-latedtothelakethermalconditionsandzooplanktonavailability. The average ¢nal length after 315 dayswas 154.4 8.8mm. The survival rates ranged be-tween 53.5% and 64.7% during the ¢rst 110 daysand 11.1^25.7% at termination. Growth rate for the¢rst2monthswasthehighestdocumentedforpejer-reyculture.This simple technique oiers the possibi-lity to produce juvenile pejerrey at a low cost andprovidesthealternativeofreinforcingthenaturalpo-pulationswith¢shalreadyadaptedtothenaturalen-vironmentalconditions.Keywords: Odontesthes bonariensis,cageculture,pampean lakes, ¢shgrowth, zooplanktivorous ¢shIntroductionThe pejerrey (Odontesthes bonariensis) is consideredas one of the most important commercial and sport¢sh species inhabiting the inland waters of Argenti-na (Bonetto & Castello1985; Grosman1995; Reartes1995; Somoza, Miranda, Berasain, Colautti, RemesLenicov & Strˇssmann 2008). Because of the highqualityof its £esh and sport ¢shing attractiveness, ithasbeenintroducedwitharelativelygoodsuccesstoother South American, European and Asian coun-tries (Loubens & Osorio1992;Toda,Tonami,Yasuda S Strˇssmann & Yasuda 2005).The inter-est in this species stimulated the ¢rst culture at-tempts for stocking at the beginning of the pastcentury. Since then, the techniques of pejerrey pro-ductionhaveimprovedprogressivelyanditispossibleat present to complete the production cycle in tanks(Miranda,Berasain,Velasco,ShirojoSRinguelet, Iriart & Escalante 1980). Because pam-pean lakesareusuallyeutrophic, zooplanktonrepre-sents an important and abundant community(Escalante 2001; Claps, Gabellone & Ben|¤tez 2004).This feature represents a unique opportunity fordeveloping pejerrey culture based on natural zoo-plankton as the source of food.The use of cages is awell-developedtechnologythathasbeenmostlyused