The mullet Mugil liza occurs along the Atlantic coast of South America from Venezuela to Argentina, but 95% of the commercial catch is collected from south Brazil between São Paulo and Argentina. Mugil liza is a single spawner with oocyte development occurring synchronously in two groups. Spawning happens in marine areas and occurs after migration. The reproductive migration occurs from Argentina (38° S) to the southern Brazilian states (24-26° S) from April to July, with peak spawning in June between northern Santa Catarina and Paraná. The presence of hyaline oocytes was associated with high salinity and sea surface temperatures of 19-21° C, and followed the seasonal northward displacement of these oceanographic conditions. The average size at first maturity (Lm ) for both sexes was 408·3 mm total length, LT . Males (Lm  = 400·1) matured earlier than females (Lm  = 421·9 mm). Fecundity ranged from 818,992 to 2,869,767 oocytes (mean = 1,624,551) in fish that were between 426 and 660 mm LT .

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Cadmium is a natural element found in the earth’s crust; it is usually associated with other metals, but due to the impacts caused by human activity, its concentration has increased in the aquatic environment. This metal may damage aquatic animal reproduction, decreasing the rate of fertilization of organisms such as fish. Thus, this study aimed to evaluate the in vitro toxicity of different concentrations of cadmium (0 (control), 0.5, 5, and 10 μg/L) using sperm cells of model organism zebrafish, Danio rerio. Structural parameters, including integrity and fluidity of the plasma membrane, concentration of oxygen species, mitochondrial function and DNA fragmentation were measured by flow cytometry. The following sperm movement parameters were also measured using the computer assisted sperm analysis (CASA) system: motility, time of motility, curvilinear velocity, average path velocity and straight line velocity in μm/s. Significant effects were observed on path speed, straight speed, curvilinear velocity, motility time, progressive and total motility, and plasma and DNA integrity. The results showed that cadmium can negatively affect some reproductive parameters in D. rerio, which may reduce the fertility rate of these animals.

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