ESTIMATE OF BRAZIL'S BREEDING STOCK AND YOUNG “ROUND FISH”

Brazil produced more than 700 thousand tons of farmed fish in 2018, of which 40% are native South American species. From the 288 thousand tons of native species, approximately 80% (230 thousand tons) are from the so-called "round fish", among which are Tambaqui (Colossoma macropomum) Pacu (Piaractus mesopotamicus), Pirapitinga (Piaractus brachypomus) and their hybrids. Tambaqui is the main round fish farmed in Brazil and has been used to produce the tambatinga and tambacu hybrids. Based on this information we estimate the amount of juveniles required to stock the Brazilian farms as well as the number of breeding stock to produce this quantity of juvenile fish. To do this simulation, after several field visits to different juvenile fish farmers, we used juvenile production data from the main laboratories that supply tambaqui for fish farms in Northern Brazil. Assuming that tambaqui and the hybrids are sold when they reach an average weight of 2 kg, to produce 230 thousand tons would require 115 million juvenile fish. Based on 20 observations over two reproduction periods in these laboratories, the data collected indicate that each spawning generates about 200,000 juveniles. It is noteworthy that this number of juveniles yielded from each spawning may vary depending on the reproductive management of each laboratory's breeding stock, as well as implicit regional factors. Thus, to produce the total round fish needed to stock Brazilian farms in 2018, 587 females were used.

Two practical observations are important from this number of female breeders: 1) twice as many animals are hormonally induced to reproduction, arising to 1,174 induced females; 2) two or three males are always used to fertilize the spawning of each female. In this case, at least 2,348 males were used. Based on these numbers, 3,522 animals would be necessary. Finally, according to the field verification obtained during the technical visits, the reproductive practices currently adopted in the production of reophilic native juveniles are inefficient, questionable, and precarious, making the final production process of juveniles not inefficient.

Acknowledgments: Coordination of Superior Level Staff Improvement - CAPES.