The preference of 0+and 2+gilthead seabream Sparus aurata for coloured substrates or no-substrate

A major component of animal welfare is to provide for the behavioural and psychological needs of captive animals. A means to estimate these needs is preference tests. However, what an animal chooses may not prove to be beneficial for its long-term health and welfare. The long-term effect (for approximately three months) of the presence of coloured substrates on gilthead seabream Sparus aurata growth performance and aggressive behaviour have been previously examined. In particular, positive results for the blue substrate (enhanced growth performance, reduced aggressive behaviour), ambiguous results for the red-brown substrate (reduced aggressive behaviour, but failed to improve growth) and no benefits for the green substrate (no differences from fish in tanks without substrate) were observed. The aim of the present study was to "ask" if and what substrate gilthead seabream prefer among those that were used in previous experiments. Binary preference tests were designed among four treatments [Blue (BS), Red-Brown (RBS), Green (GS) Substrate or no substrate-Control (C)]. Trials were performed for two age classes (0+ and 2+) and fish were tested individually (10 fish per trial) or in groups of 7 fish (in triplicate). Fish choices were similar either tested individually or in groups. Older gilthead seabream preferred the BS in all dual combinations, chose the RBS only in cases that the BS was not present and did not prefer the GS. Younger gilthead seabream chose the BS over the C, preferred the RBS in certain combinations and did not prefer the GS. Moreover, in the combinations of two substrates an increased frequency of changing compartments was observed. Obtained results indicate that gilthead seabream choices were not always in line with long-term effects of substrates. However, these outcomes could be strengthened if motivational tests were performed to confirm that these choices are of some value for gilthead seabream. (C) 2013 Elsevier B.V. All rights reserved.