For the production and commercialization of ornamental fish species, it is indispensable to collect biometric data for the selection of animals for trade and genetic improvement of the stock. However, during handling processes, fishes receive more stress if proper anesthetics are not used. Thus, using appropriate anesthetics is an important tool for minimizing stress in animals. The objective of this study was to determine the effective concentrations of benzocaine, eugenol and menthol for angelfish (Pterophyllum scalare) anesthesia and to develop induction and recovery response curves for different concentrations of these anesthetics. A total of 75 fish were exposed to five concentrations of three different anesthetics, benzocaine (60, 85, 110, 135 and 160 mg L⁻¹), eugenol (40, 80, 120, 160 and 200 mg L⁻¹) and menthol (50, 75, 150, 200 and 250 mg L⁻¹) in a completely randomized design. Each concentration (5 fish per concentration) consisted of five replicates and each replicate was represented by a single fish (1 fish per replicate). The results indicate that the tested substances have met the criteria of anesthetic efficiency. The effective concentrations of benzocaine, eugenol and menthol determined to be 89.25 mg L⁻¹, 90.6 mg L⁻¹ and 92.1 mg L⁻¹, respectively for the anesthesia of freshwater angelfish.

Describing animal growth rate using non-linear models allows a detailed evaluation of growth behavior. Four non-linear models were used to fit weight gain and total length data of bullfrog (Lithobates catesbeianus) tadpoles, as follows: Gompertz, Y = A exp (-exp (-b (t-T))); Von Bertalanffy, Y = A (1 - K exp (-B t))³; Logistic, Y = A (1+ K exp (-B t))-1 and Brody, Y=A (1 - K exp (-B t)). We used 3,240 tadpoles, with average initial weight 0.044 g and average total length 12.79 mm, stage 25 Gosner. The measurements were conducted every ten days on 10% of the animals in every tank. The criteria used to select the model that best described the growth curve were: Residual Mean Square (RMS); determination coefficient (R²); residual graphical analysis; residual mean absolute deviation (MAD). Brody mathematical model was not a good fit for weight gain and total length, while Von Bertalanffy model underestimated tadpole initial weight, thus showing the difficulty of mathematical models to describe biological data at this growth stage. However, the Gompertz and Logistic models were considered to be an adequate fitting to describe growth rate and total length of bullfrog tadpoles in captivity.