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Effects of temperature and salinity on bilateral symmetry of Eugerres brasilianus (Cuvier, 1830) larvae: Implications for Brazilian mojarra rearing

Evangelista, Isis Ribeiro, dos Santos, Luciano Neves, dos Santos, Alejandra Filippo Gonzalez Neves
Aquaculture 2019 pp. 734327
Eugerres, adverse effects, asymmetry, environmental factors, eyes, fish culture, fish farms, fish larvae, marine fish, primary sector, rearing, salinity, t-test, temperature, yolk sac, Brazil
In Brazil, marine fish farming have minor contribution to the primary sector, but some species have shown great potential, such as the Brazilian mojarra, Eugerres brasilianus. However, larviculture is still a bottleneck due to the lack of protocols supporting survival and performance. Fluctuating Asymmetry (FA), which is the random deviation in bilateral symmetry in response to environmental conditions, can be used as a proxy of fish performance. The main purpose of this study was to evaluate, through microcosms experiments whether the FA levels in larvae of E. brasilianus will change with different temperatures (20 °C, 25° and 30°) and salinities (25, 30 and 35). A total of 92 larvae were analyzed. The Student t-test (p = .53) rejected the occurrence of directional asymmetry and validated the presence of FA in larvae's. The survival of larvae did not differ significantly under different temperatures (PERMANOVA; p = .58) and salinity (p = .68), probably because the early larval stage (i.e. before yolk sac assimilation) and short duration of the experiments. Eye asymmetry changed significantly among temperatures (PERMANOVA; p = .0001), but not with salinity (PERMANOVA; p = .77), revealing that waters ≤20 °C might have adverse effects on the Brazilian mojarra. This species is eurihaline, tolerating a wide range of salinity, explaining thus the null effect of this variable on eye asymmetry. However, eye asymmetry at lower temperatures may reduce the visual acuity of Brazilian mojarra, decreasing, therefore, the individual aptitude for food searching and intake, and affecting thus the zootechnical performance of this species in fish farms.