The number of tilapia producers in Brazil follows the growing demand of the national aquaculture sector. The Brazilian territorial area is very wide, having a climatic division with six regions : equatorial, tropical, semi-arid, high-altitude tropical, tropical Atlantic and subtropical, which can directly influence the production process of fish. Considering only the São Paulo State , we found several climatic micro-regions, each one has particularity like high and low annual rainfall indices, regions between valleys and plains, different photoperiods, rainfall indices and temperature. These differences can directly influence the management of fish farms, reflecting on the storage biomass, reproductive period and egg production and influencing the production costs, harming the breeder.
The present study aims to evaluate the reproductive frequency of Nile tilapia matrices in “hapas” , analysing the absolute fecundity, hatching rate and total number of larvae produced . Nile tilapia (150 specimens) were stocked in January 2023 : 100 were females (300 ± 20 g) and 50 males (300 ± 20 g) distributed one family per "hapa", totaling 25 families. The "hapas" (1.0 mm mesh, measuring 3.0 x 1.5 x1.5 m) were installed in two earthen nurseries (300 m2 ), the animals (2 females/1 male ) identified and conditioned for starting the cohort and copulation in the "hapas ". R eproduction units were evaluated weekly, collecting the eggs in the mouth of the females, and taken to the laboratory. Absolute fecundity (number of eggs per clutch), hatching rate (number of hatched larvae 100/number of incubated eggs) and total number of larvae were evaluated for each female eggs. Six samples were carried out between January and February 2023 . In January the reproductive frequency was 31.21 ± 2.09% and in February 16.67 ± 11.03%, with a reduction of 51.81%.
When evaluated the absolute fecundity between the months, was observed in January 2,311.60 ± 104.80 eggs per clutch and in February, 1,670.47 ± 343.33, with a reduction in the number of eggs produced of 27.74%. The mean hatching rate in January was 50.70 ± 6.45 % and in February it was 32.53 ± 11.5 %, with a reduction of 36%. Total number of hatched larvae also followed the same pattern, 16,505 larvae produced in January and 10,033 in February, a reduction of 40%. The water temperature did not vary between the two months with an average of 27.4°C. R eproductive period of Nile tilapia in the tropical regions of Brazil varies from October to March, it was observed the reproductive frequency decreases throughout the reproductive cycle, so studies that determine the best reproductive phase are of paramount importance to optimize financial resources. and biological for an increasingly sustainable production system.