Percorrer por autor "Refojos, Benjamin Costas"
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- Effect of high densities on growth, stress response and plasma amino acid levels in senegalese sole (Solea senegalensis, Kaup 1858)Publication . Refojos, Benjamin Costas; Conceição, LuísFish are exposed to stressors in artificial conditions such as in aquaculture. Changes resulting from the stress response divert energy from normal metabolic processes including growth, to deliver energy to the physiological systems activated to adapt to a stressor. Fish held at high stocking densities are generally considered to be exposed to chronic stressor situations that predispose the fish to infection, reproductive impairment, and may impose severe energy demands. In the present study, 144 sexually immature Senegalese sole {Solea senegalensis) ']u\Qn\\QS of 78.8 ± 18.9 g (mean ± S.D.) were maintained at low (8 fish; 3.05 kg/m2 at the start of the experiment), médium (16 fish; 6.1 kg/m2) and high (24 fish; 9.14 kg/m2) stocking densities during a period of 63 days. While growth and food consumption did not vary among different stocking densities, cortisol, glucose and free amino acids showed significant differences among different stocking densities. Results point to médium and high stocking densities as stressful rearing conditions, showing different results among fish held at médium and high stocking densities, which may be due to different strategies for coping with stress at different densities. Moreover, several disease outbreaks were observed in fish reared at high stocking densities, but not at the other densities. In addition, fish held at high stocking density apparently used higher amounts of indispensable amino acids (IAA) than the remaining fish. This preferential usage may be due to higher demand for energy production, directly or after transformation to dispensable amino acids in order to cope with stressful conditions, or due to synthesis of other important metabolites related to stress response. This study also suggests a wide intraspecific variability to stress response in Senegalese sole, which defines if a fish will or not adapt to different stocking densities. In summary, high stocking density may be a stressful condition for Senegalese sole, which affects resistance to disease but not growth and may affect IAA requirements.