The aim of this work was to determine the amounts of copper, zinc, cadmium and lead which enter the tanks of the maternity section of a Mexican commercial hatchery, and those that are discharged to the environment. The most important inputs of Cu were chemicals for water treatment and disease prevention, feeds and the metal dissolved in influent water. Suspended solids and feeds were the two most important inputs of Zn, and feeds and chemicals were the main sources of Pb and Cd. Most metal concentrations may be considered safe for shrimp culture, but the concentrations of Cd of three formulated diets were close or above safe levels. The annual 2013 output of this hatchery was approximately 1.3x10(9) post-larvae, and the estimated metals discharged to the environment by the maternity section were 351 g of Cu, 1,190 g of Zn and 1.35 and 0.02 g of Pb and Cd, respectively. The amounts of Pb and Cd are equivalent to those of the fertilizers spread on between 0.5 and 1.5 ha of the agricultural land of Sinaloa State.