World Aquaculture December 2020

70 DECEMBER 2020 • WORLD AQUACULTURE • WWW.WA S.ORG this variable. The low density used in our study (1.5 crayfish/m 2 ) may have fostered greater survival. Feed Conversion Ratio Feed conversion ratio (FCR) for polyculture, where only tilapia were fed, was 1.42, while for monoculture it was 1.49. The values obtained in this study are lower than those reported in the literature. Wicki et al . (2008) reported FCRs of 3.45 and 3.74 after 240 days. Metts et al. (2007) reported FCR values of 2.72 and 2.79 using alfalfa hay and supplemental feed, but FCR was not available for the use of alfalfa hay as fertilizer. Metts et al . (2009) reported FCR of 3.25 and 4.13 using diets with different protein levels. Tilapia in polyculture had a mean FCR of 1.41, while Martin et al. (2007) reported FCR of 1.30 and Tidwell et al . (2007) had FCR values between 1.66 and 2.07 for polyculture. Even though this variable must be reduced further, the values obtained are within the range reported by those studies. Production Crayfish yield was about 600 kg/ha for both culture systems. The average red claw production was 585 kg/ha for the polyculture system and 665 kg/ha for monoculture, without statistical significant differences. Wicki et al. (2008) obtained 809 kg/ha at 2 crayfish/m 2 . Metts et al . (2007) reported yields of 617 kg/ha for culture with alfalfa hay as fertilizer and 882 and 968 kg/ha for those with supplemental feed at 3/m 2 density. Mean global crop for polyculture was of 2,083 kg/ha and 2,161 kg/ha, resulting in an average overall production of 2,121 kg/ha with statistically significant difference regarding monoculture. Rodgers et al . (2006) showed yield differences among all-male tilapia culture (1,452 kg/ha) and female and mixed-sex culture (1,180 and 1,150 kg/ha) related to better growth of males. Tilapia grows better at low densities (1-3/m 2 ) although production increases at higher densities. The overall tilapia production reached in polyculture (2,120 kg/ha) did not affect red claw growth until the final sizes obtained. Polyculture allows similar red claw yield than monoculture without feeding the species. Rouse and Kahn (1998) obtained total production of 2,163 and 3,445 kg/ha in red claw-tilapia polyculture stocked at 0.5 and 1 crayfish-tilapia/m 2 . They observed high red clawmortality (76 and 81 percent) resulting in poor crayfish yield (225 and 182 kg/ha). The low crayfish growth and high mortality is related to the feeding behavior of tilapia. Barki et al . (2001) and Rouse and Kahn (1998) suggested that red claw is affected by tilapia in polyculture but the magnitude of this effect is related to fish size. In the presence of large fish, survival and growth of red claw is reduced (Barki et al. 2001). In the present study, no negative aspects related to red claw mortality or lower growth were revealed in the two systems tested. Further studies are necessary to achieve larger sizes of tilapia and desired crayfish sizes. Notes GustavoWicki and Rolando Hernández Centro Nacional de Desarrollo Acuícola (CENADAC) Ministerio de Agricultura Ganadería y Pesca- Subsecretaría de Pesca y Acuicultura. Paseo Colón 982- 1063- CABA- Argentina. Corresponding author: guswicki@gmail.com References Barki, A., N. Gur and I. Karplus. 2001. Management of interspecific food competition in fish-crayfish communal culture: the effects of the spatial and temporal separation of feed. Aquaculture 201:343- 354. Boyd, C. 1998. Water and bottom soil quality management in freshwater aquaculture ponds. Annais do Aquaculture 1:303-312. Jones, C.M. 1997. The biology and aquaculture potential of the tropical freshwater crayfish, Cherax quadricarinatus . Available: http://www. researchgate.net/profile/Clive_Jones3/ Martin, S., G. Wicki and F. Rossi. 2007. Engorde de tilapia del nilo ( Oreochromis niloticus ) en jaulas de pequeño volumen con dos alimentos de diferente composición. In: Desarrollo y utilización de ensilado ácido como componente de alimento para peces. SAGPYA -FAO, 31-43. Metts, L., K.R. Thompson, Y. Xiong, B. Kong, C.D. Webster and Y. Brady. 2007. Use of alfalfa hay, compared to feeding practical diets containing two protein levels, on growth, survival, body composition, and processing traits of Australian red claw crayfish, Cherax quadricarinatus , grown in ponds. Journal of the World Aquaculture Society 38(2):218-230. Metts, L.S., K. Thompson, L. Muzinic and C. Webster, 2009. Effect of feeding practical diets containing different protein levels to Australian red claw ( Cherax quadricarinatus ). World Aquaculture 40(1):16-18. Rodgers, L.J, P. Saoud and D. Rouse. 2006. The effect of monosex culture and stocking density on survival, growth and yield of redclaw crayfish ( Cherax quadricarinatus ) in earthen ponds. Aquaculture 259:164-168. Rouse, D. and B. Kahn. 1998. Production of Australian red claw Cherax quadricarinatus in polyculture with Nile tilapia Oreochomis niloticus . Journal of the World Aquaculture Society 29:340-344. Silva, L.B., L.J.G. Barcellos, R.M. Quevedo, S.M.G. Souza, L.C. Kreutz, F. Ritter, J.A. Finco and A.C. Bedin. 2006. Alternative species for traditional carp polyculture in southern South America: Initial growing period. Aquaculture 255:417-428. Thompson, K.R., L.A. Muzinic, L. S Engler, S. Morton and C.D. Webster. 2004. Effects of feeding practical diets containing various protein levels on growth, survival, body composition, and processing traits of Australian red claw crayfish ( Cherax quadricarinatus ) and on pond water quality. Aquaculture Research 35:659-668. Tidwell, J., S. Coyle, A. Van Arnum, C. Weibel and S. Harkins. 2000. Growth, survival and body composition of cage cultured Nile tilapia Oreochromis niloticus fed pelleted and unpelleted distillers grains with solubles in polyculture with freshwater prawn Macrobrachium rosenbergii . Journal of the World Aquaculture Society 31:627-631. Wicki, G., M. Martinez, E. Wiltchiensky, P. Maizels, S. Panné and L. Luchini. 1998. Ensayo de producción de policultivo de camarón de agua dulce ( Macrobrachium rosenbergii Palamonidae) y pacú ( Piaractus mesopotamicus Characidae). Natura Neotropicalis 29(1):69-73. Wicki G. and L. Luchini. 2004. Development of practical diets for pacú, a South American fish species. International Aquafeed 7:23-29. Wicki, G., F. Rossi, O. Merino and L. Luchini. 2008. Engorde de la langosta de pinzas rojas ( Cherax quadricarinatus ), en el subtrópico argentino: primeros resultados. http://www.minagri.gob.ar/site/pesca/ acuicultura/01=cultivos/01-especiess/index.php