Gilthead seabream (Sparus aurata) response to three music stimuli (Mozart--"Eine Kleine Nachtmusik," Anonymous--"Romanza," Bach--"Violin Concerto No. 1") and white noise under recirculating water conditions.

This study presents the results of the response of Sparus aurata to three different musical stimuli, derived from the transmission (4 h per day, 5 days per week) of particular music pieces by Mozart, Romanza and Bach (140 dB(rms) re 1 µPa), compared to the same transmission level of white noise, while the underwater ambient noise in all the experimental tanks was 121 dB(rms) re 1 µPa. Using recirculating sea water facilities, 10 groups, 2 for each treatment, of 20 specimens of 11.2 ± 0.02 g (S.E.), were reared for 94 days, under 150 ± 10 l× 12L-12D, and were fed an artificial diet three times per day. Fish body weight showed significant differences after 55 days, while its maximum level was observed after the 69th day until the end of the experiment, the highest value demonstrated in Mozart (M) groups, followed by those of Romanza (R), Bach (B), control (C) and white noise (WN). SGR (M = B), %WG (M = B) and FCR (all groups fed same % b.w.) were also improved for M group. Brain neurotransmitters results exhibited significant differences in DA-dopamine, (M > B), 5HIAA (C > B), 5HIAA:5HT (WN > R), DOPAC (M > B), DOPAC:DA and (DOPAC + HVA):DA, (C > M), while no significant differences were observed in 5HT, NA, HVA and HVA:DA. No differences were observed in biometric measurements, protease activity, % fatty acids of fillet, visceral fat and liver, while differences were observed regarding carbohydrase activity and the amount (mg/g w.w.) of some fatty acids in liver, fillet and visceral fat. In conclusion, present results confirm those reported for S. aurata, concerning the observed relaxing influence--due to its brain neurotransmitters action--of the transmission of Mozart music (compared to R and B), which resulted in the achievement of maximum growth rate, body weight and improved FCR. This conclusion definitely supports the musical "understanding" and sensitivity of S. aurata to music stimuli as well as suggesting a specific effect of white noise.

Environmental enrichment induces changes in brain monoamine levels in gilthead seabream Sparus aurata.

It is generally accepted that environmental enrichment enhances the performance and improves welfare of animals kept in captivity. Similar results have been obtained for fish. It has been previously reported that the presence of Blue or Red-Brown Substrate (BS and RBS respectively) on tank bottom resulted in growth enhancement and suppression of aggressive behavior of gilthead seabream Sparus aurata compared to Green Substrate (GS) and tanks without modifications (Control-C). In an attempt to identify the underlying mechanisms, in the present study the effects of this environmental enrichment on brain monoamine neurotransmitters and fatty acids of gilthead seabream were evaluated. BS and RBS fish had lower serotonergic activity (5-HIAA/5-HT), resulting mainly from lower 5-hydroxyindoleacetic acid (5-HIAA) levels. BS fish also had lower serotonin levels compared to all other treatments. Brain noradrenaline (NA) levels did not show significant differences between substrate treatments and control. Brain dopamine (DA) levels were lowest in BS and RBS fish, higher in GS fish and highest in C fish. No differences were observed for dopamine metabolites or dopaminergic activity. Moreover, brain NA was negatively correlated with body weight in BS fish and positively correlated in RBS and C fish. A positive correlation was also observed for brain DA with body weight in RBS fish. No differences were observed for brain fatty acids. Present results support the hypothesis that the beneficial effects of the presence of BS and RBS are related to altered social interactions and indicate the establishment of a less stressful social organization in enriched-reared fish groups.

Effects of environmental enrichment on growth, aggressive behaviour and brain monoamines of gilthead seabream Sparus aurata reared under different social conditions.

The presence of blue or red-brown substrate on the tank bottom has been previously reported as an efficient means of environmental enrichment for gilthead seabream. The present study aimed to investigate whether this enrichment is still beneficial when gilthead seabream is reared under different social conditions (i.e. a lower 4.9 kg m(-3) and a higher 9.7 kg m(-3) density). Water exchange was adjusted according to fish biomass to exclude density effects on water quality. In the enriched tanks single-colour glass gravel was used as substrate (blue and red-brown substrate, or BS and RBS respectively), while control tanks had no gravel. Growth, aggressive behaviour and size distribution results indicated that the lower density created a less favourable social environment. In both densities studied, BS enhanced growth, suppressed aggression and reduced brain serotonergic activity. In the condition of intense social interactions (i.e. the lower density) BS also reduced brain dopaminergic activity. These results along with the negative correlations observed between brain monoamines and fish body mass, indicated that substrate and density effects are socially-induced. However, there may be several biotic and/or abiotic factors interfering with substrate effects that should be investigated before the practical use of a substrate in land-based intensive aquaculture.