The in vitro hydrolysis of different starches (potato, rice, wheat, corn, sorghum), as well as an intermediate product of malting process (brewer's spent grain), by blue tilapia, Oreochromis aureus, gilthead sea bream, Sparus aurata and European sea bass, Dicentrarchus labrax, were compared (total carbohydrase assay, 37° C, pH 7.6,4 hours incubation). Obtained results (significandy higher hydrolysis levels obtained for potato, rice and sorghum starch) suggest that starch source and associated properties (starch granule size, amylose content) and modifications applied may have significant difference on its digestion by fish digestive carbohydrases. Furthermore, the importance of brewer's spent grain as a low-cost carbohydrate source and feed component, in relation to aglucosidase adaptive response to dietary carbohydrate, is also considered significant.

Sharpsnout seabream Diplodus puntazzo has been successfully introduced in Mediterranean aquaculture for reasons of species diversification. However, there is limited information related to specific rearing conditions that the species may require for production optimization in land-based aquaculture. The aim of the present study was to investigate the combined effects of rearing density and background colour on growth performance of sharpsnout sea bream D. puntazzo reared in a recirculating water system. Juveniles (4.0 ± 0.03 g) were reared (duplicated groups) under low (D 16 fish tank−1 or 1 kg m−3) and high (3D 48 fish tank−1 or 3 kg m−3) density in white, light blue and black tanks for 88 days. During the first 53 days of rearing, fish under low density presented better growth than fish under high density. However, in the following period (days 53–88) SGR in 3D-reared fish was significantly higher than in D-reared fish, resulting in no mass differences on day 88. Regardless of rearing density effects, black tanks had a negative effect on growth and should be avoided in sharpsnout sea bream rearing. Within the life stage studied, present growth results, along with those of fish groups homogeneity (coefficient of mass variation, frequency distribution of mass), indicate a change in social interactions according to body size. It is suggested that juvenile sharpsnout seabream should be stocked at low density until they reach approximately 16 g. Afterwards, a higher density seems more appropriate for this species while it also ensures a higher productivity.

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 dBrms re 1 μPa), compared to the same transmission level of white noise, while the underwater ambient noise in all the experimental tanks was 121 dBrms 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.

Two musical stimuli transmissions (Mozart and Romanza) as compared with white noise treatment or control, both resulted in significantly higher growth performance in juvenile (6.7 +/- 0.12 g) rainbow trout (Oncorhynchus mykiss) reared for 14 weeks. Carcass chemical composition and fatty acid composition (% of total fatty acids and mg/g carcass wet weight) did not differ among experimental treatments. The same was observed with regard to liver composition. Brain serotonin (5-HT) and its metabolite (5-HIAA) levels were increased in Mozart fish groups compared to all other treatments. However, serotonergic activity (as defined by the 5-HIAA: 5-HT ratio) for the Mozart groups was similar to control groups and was increased in Romanza and white noise fish groups. Brain dopaminergic activity (as defined by the DOPAC: DA ratio, i.e. dopamine metabolite to dopamine levels) was lower in Mozart compared to control fish groups. Differences were also observed as regards total carbohydrase and protease activity in several parts of the digestive tract.In conclusion, the results of the present data indicate that the musical stimuli transmitted were beneficial for the growth performance of rainbow trout. The fact that white noise treatment presented no major differences from control fish groups suggests that this specific stimulus was neither beneficially nor negatively perceived by rainbow trout, while it further supports the hypothesis that it is the musical stimuli per se that make all the difference. (C) 2013 Elsevier B.V. All rights reserved.

Though fish farming has existed for hundreds of years, over the past several decades the practice has expanded significantly because of its major importance in terms of both, nutrition, economics and ecology, accumulated experience revealing that it may be conducted by means of a variety of production systems in accordance with circumstances. Today, thanks to numerous novel techniques developed in the 20th century as well as because of the pressures of growing demand, continuously updated knowledge is being applied aiming to attain the highest possible level of pursued results/achievements. This has led to the creation of diverse fish farming production systems operating, quantitatively and qualitatively, according to the level of technology used. In the present-day setting of gravely compromised environments worldwide, this brought about due to mounting population numbers and their increasing demands, all efforts to lighten the human burden on the planet must be encouraged. One promising means is the contribution to people's nutritional needs in an economically attractive and environmentally-friendly manner through the boosting of farmed fish production levels, particularly by using the recirculated (closed or semi-closed) aquaculture/water system. It is the only fish farming procedure that offers not only a high quality of the final product but also full environmental conservation, optimal use of technological/biotechnological possibilities and, most importantly, farmed fish "happiness" and welfare.

As is well known, optimal levels of both homeostasis and welfare of farmed fish are almost completely dependent upon human endeavour to investigate fish brain capacities and utilize them for the greatest benefit. According to the accumulated research experience specifically concerning minimization of farmed fish stress, the final outcome of the involved mechanisms is strongly associated with fish species and biological stage as well as a number of rearing environment parameters related to the type of the production system applied. Based on the conclusions gained, it is clear that the fish brain-neuroendocrinological system is an extraordinarily rich and expressive one forming a species-specific living ethology that incorporates cognitive behaviour and ‘demands’, the whole constituting, in effect, the fish “personality”. The diverse facets of this ‘personality’ are expressed via a wide range of phenomena: e.g. the power of learning, memorizing, sound production, particular external coloration changes, courtship behaviour, parent care and “emotional feelings” including the manifestation of aggressiveness and the demonstration of “happiness”. The final conclusion to be drawn is that fish are indeed amazing creatures. One can only marvel at the superb plasticity of their brain which, over hundreds of millions of years and through myriad genomic, evolutionary and epigenetic developments, has enabled them to adapt and respond to and remarkably thrive in all extremes of environments, and all this though they lack a cerebral neocortex.

Recent data suggest that specific light wavelength can alleviate fish acute stress response by counteracting or reducing the stress-induced cortisol increase. The European sea bass Dicentrarchus labrax, widely reared in the Mediterranean, is very sensitive to handling stress, so that typical rearing procedures during on-growing (e.g. grading) are avoided. The present study aimed at investigating whether exposure to blue (480nm) or white light (BL or WL, respectively) could alleviate European sea bass acute stress response. Fish (initial weight 130.9±0.4g) were reared (seawater recirculating system) for 63days under BL or WL and then subjected to 1 hour confinement or left undisturbed (control). Confinement of fish under BL resulted in a higher cortisol increase, no dopaminergic activation and lower brain serotonergic activity than under WL. In contrast, WL confined fish showed a lower cortisol increase coupled with higher brain serotonergic activity and increased levels of brain dopamine. Stress-induced hematocrit increase was lower when fish were confined under BL and triacylglycerides increase was only observed for WL reared fish. Differences in some parameters between unstressed BL and WL fish suggest that light wavelength had an effect on fish physiological status irrespective of stress. Although present results are not conclusive on which fish groups were more or less stressed, they do confirm that light wavelength can differentiate European sea bass response to acute stressors. Further studies to elucidate biological mechanisms of light spectrum effects will reinforce its efficacy as a tool to manipulate intensively reared fish stress response.

It is well known that fish vision and spectrum perception are strongly related to each species natural habitat and living ethology. Recent research data clearly indicate that light spectrum affects farmed fish stress response, physiological status, behaviour, and consequently growth performance. This study aimed to investigate the effects of white (full-spectrum), red (605nm) and blue (480nm) light on common carp reared in a recirculating water system. Two experiments were conducted. The first (Experiment 1) was performed on scaled carp (14.68±0.14g, duration 158 days) combining light treatment with two stocking densities (low: 10specimenstank−1 or 1.22kgm−3 and high: 40specimenstank−1 or 4.89kgm−3). The second (Experiment 2) investigated the effects of light spectrum in mirror carp (51.88±0.46g, duration 143 days) combined with two light intensities (150 and 300lx). Within the fish life stage examined and duration of present experiments, it is indicated that scaled common carp should be reared under red illumination when at low stocking density and blue illumination when at high stocking density. For the rearing of mirror carp, blue or red light should be avoided since they induced an increase in size heterogeneity. Present results also underline the importance of lighting conditions on reared common carp physiological status. Changing light spectrum in indoor recirculating water systems is easy, cost efficient and appropriate manipulation could befit reared fish welfare.

. CSBE100303 - Presented at Section II-B: Aquacultural Engineering Conference ABSTRACT Fish farming prospects depend on the type of production system and the level of management. Therefore, the level of fish homeostasis and stress are important factors during their rearing period. Fish receive environmental stimuli mainly by their body receptors and react to them by an infinite number of outcomes influenced by various neurohormonal-biochemical processes. Using Recirculating Water Systems (RWSs), a notable reduction of undesirable hormonal and metabolic-biochemical functions could be easily achieved by preserving a proper combination of rearing water characteristics with tank size, fish rearing density, feeding practice and fish living ethology demands. These results could be further enhanced by combining the above mentioned parameters with rearing tank color and certain lighting conditions (photoperiod, spectrum, intensity). Also, by transmission of classical music into the fish rearing tanks, RWS facilities and proper rearing management can considerably contribute towards enhancing most fish anti-stress neurohormonal functions. That means that fish can feel closer to the way they should by living in their environment, without, however, facing its difficulties (e.g. enemies, water pollution, climate change). So, RWSs can provide for fish an excellent artificial natural living environment, while their construction and operation costs could be remarkably reduced not only by their low water requirements but also by using proper material, renewable energy resources and integration with aquaponics practices. Under these rearing conditions fish, being almost happy, can show the highest possible levels of growth rate, final product quality and welfare, ensuring the farmers and consumers satisfaction as well.

The objective of this study was to further investigate the effects of music on fish physiology, bearing in mind available information regarding the involvement of endogenous and exogenous factors in fish farming. Therefore, Cyprinus carpio (50.5 ± 0.36 g) were reared in a recirculating water system under 80 and 200 lux and subjected to no music at all (control, ambient noise only), 4 h of Mozart’s “Eine Kleine Nachtmusik”, or 4 h of anonymous “Romanza-Jeux Interdits” for 106 days. Both music treatments resulted in increased growth performance at both light intensities, with Romanza treatment at 200 lux resulting in better growth performance than Mozart treatment. Furthermore, feed efficiency for the Romanza groups was significantly better than for the control. Although no significant music effect was apparent for brain neurotransmitters, lower anterior intestine alkaline protease levels were detected for both music treatments. Taking into consideration the numerous advantages of recirculating water systems, it should be emphasised that fish response to music expresses the results of various physiological and biochemical processes, especially when fish notably respond differently when subjected to two different pieces of music.

The aim of the present study was to evaluate music effects (Mozart, K525) on gilthead seabream Sparus aurata and investigate whether its response to music was differentiated when combined with different lighting conditions. Therefore, S. aurata (mean ± s . e . 1·51 ± 0·01 g) were reared in re‐circulating water system under 80 and 200 lx and subjected to 2 and 4 h of music transmissions or to no music at all (control, ambient noise only). Underwater ambient noise of the equipment ( e.g. pumps and aerators) in all experimental tanks was 121 dB re 1 μPa and music transmitted was set at 140 dB re 1 μPa. During the first 89 days of rearing, music resulted in enhanced growth. Nevertheless, at the end of the experiment (on day 117) no significant differences were found for body mass but music treatment resulted in more homogeneous fish populations than controls. Brain neurotransmitter levels were reduced especially when music transmission was combined with 200 lx. Feed utilization was significantly improved when fish were subjected to 4 h of music and 200 lx, while stomach proteolytic enzymes and intestine total carbohydrases were lower and higher, respectively, compared to controls. Some differences were also observed in liver and plasma fatty acids composition. The present results provide the initial evidence that music transmission under specific rearing conditions could have enhancing effects on S. aurata growth performance, at least at specific fish sizes. Moreover, the observed music effects on several aspects of fish physiology ( e.g. digestive enzymes, fatty acid composition and brain neurotransmitters) imply that music could possibly provide even further enhancement in growth, quality, welfare and production.

Fish growth and physiology may be affected by light spectrum, which can be easily manipulated in indoor aquaculture facilities, and especially recirculating water systems, with little cost. Since data related to light spectrum and widely reared fish are still few, the present study aimed to investigate the effects of coloured light on growth performance and stress response to confinement of rainbow trout Oncorhynchus mykiss. Fish (145.3±1.5g) were reared under white (full spectrum, fluorescent lamps), red (605nm) and blue (480nm) light (lamps covered with appropriate filters) for 111 days under recirculating water systems (150lx, 12L–12D). At the end of the experimental period and for each light treatment, fish were either subjected for 1h to confinement stress or remained undisturbed (control groups). Total length of the fish reared under red light was greater than that of the other regimes, whereas other growth parameters showed a similar trend but were not significantly different from one another. Carcass proximate composition was not affected by light spectrum. Fish exposed to confinement showed typical primary (high cortisol) and secondary (high glucose and haematocrit, liver lipid mobilization, osmotic and ionic disturbances, blood acidosis, etc.) stress responses. Nevertheless, in fish reared under blue light, stress-induced cortisol increase was lower and liver lipids mobilization was absent compared with white light (significant interaction). Present results indicate that if stressors are kept to a minimum then red light could be suggested for the intensive rearing of rainbow trout.

Previously reported data clearly indicate that depending on species, ambient light spectrum can affect fish growth, physiology, behaviour, reproduction, etc. Since light spectrum can be easily controlled in intensive indoor fish farming facilities, the present study aimed to investigate the effects of coloured light on growth performance (body weight, growth rate, food utilization, carcass composition, etc.) and physiological status (blood and plasma parameters, brain neurotransmitters, tissue fatty acid composition, etc.) of two widely reared fish species, gilthead seabream Sparus aurata and rainbow trout Oncorhynchus mykiss. For this purpose, 240 specimens of S. aurata (29.8 ± 0.13 g) and 60 specimens of O. mykiss (71.4 ± 0.30 g) were exposed to white (full-spectrum, fluorescent lamps), red (605 nm) and blue (480 nm) light (lamps covered with appropriate filters) for 11 weeks under recirculating water systems. Blue light had a significantly negative impact on O. mykiss growth performance accompanied with reduced liver total lipids and plasma glucose and increased brain serotonergic and dopaminergic activity. In the case of S. aurata, red light significantly increased brain dopaminergic activity, while a tendency towards reduced growth was also observed. Since these results indicated the establishment of stressful conditions, O. mykiss and S. aurata should not be reared under blue and red light, respectively. For each species, the effect of the remaining light colours tested, was not clearly differentiated so that an appropriate light spectrum for the most efficient farming of O. mykiss and S. aurata could not be suggested, at least for the time period examined. Nevertheless, present results suggest that light colour should be regarded as a rearing factor worth to be further investigated, especially when recirculating systems are concerned.

Appropriate rearing conditions for successful farming of white sea bream Diplodus sargus L. have not yet been studied in depth, while one of the major problems is the species increased aggressiveness. Given the known effect of density and background colour on fish growth, welfare and social behaviour, the present study aimed to investigate whether the two factors combined could favour D. sargus performance. Juveniles (17.37 +/- 0.06 g) were reared in white, light blue and black tanks under low (7 fish tank(-1) or 1.96 kg m(-3)) and high (28 fish tank(-1) or 7.79 kg m(-3)) density for 87 days. Water quality was not affected by experimental treatments. The best overall performance (growth, food utilization, body protein content, liver fatty acids) was achieved under low density and white or light blue tanks. Increased incidence of social interactions was indicated in fish under high density or when reared in light blue and black tanks. The present results clearly suggested that the use of black tanks should be avoided. On the other hand, stocking D. sargus at a density of up to 7.79 kg m(-3) may be feasible because productivity was greater even if growth was slower. In this case, however, the use of white tanks is highly recommended.

It is well known that music could have relaxing and antidepressant effects on humans, other mammals and birds. The present study aimed to evaluate music effects on common carp Cyprinus carpio growth and physiology, under different light conditions. Therefore, common carp (130.9±0.67g) was reared, in recirculating water system, under constant darkness (D) or normally illuminated conditions (L) for 12 weeks. Classical music was transmitted underwater and music treatments consisted of no music at all (control groups, C) and three music transmissions either of 30min duration at 1.5h intervals (M30) or of 60min duration at 1h intervals (M60). Obtained results showed that light conditions had a negative effect on fish growth (L–C versus D–C, P<0.01), but when 30min music was transmitted (L-M30) growth was improved and equal to D–C. Fish groups presenting reduced growth exhibited significantly increased brain neurotransmitters levels, indicating the occurrence of stressful conditions. Also, music transmission significantly affected carcass and liver fatty acid composition. Present results showed that music could be regarded as a stress relieving or inducing factor. Possible use of music as a growth and product quality promoter, as well as a means to ensure fish welfare under intensive fish farming is discussed.

Although the growth of intensively reared sharpsnout seabream Diplodus puntazzo (DP) has been suggested to improve in duoculture with gilthead seabream Sparus aurata (SA), the stocking ratio for most effective duoculture rearing has not been investigated. For this purpose, juvenile D. puntazzo (1.68 +/- 0.011 g) and S. aurata (1.43 +/- 0.007 g) were reared in duplicated groups of 165 specimens each, in two monoculture (100% DP, 100% SA) and four duoculture combinations (80% DP-20% SA, 60% DP-40% SA, 40% DP-60% SA, 20% DP-80% SA) for 96 days under recirculated water system conditions. Both species exhibited the highest growth when stocked at 20% and the poorest growth when stocked at 80%. For each species, no major differences for coefficient of weight variation and carcass proximate composition were detected. As the percentage of stocked S. aurata increased, D. puntazzo aggressiveness and weight variability of whole population were reduced, while total biomass, food consumption and food conversion ratio were increased. The results obtained are discussed in relation to fish behaviour and social interactions. From the fish farming point of view, it is indicated that under the present experimental conditions, juvenile S. aurata should be reared in monoculture and D. puntazzo in duoculture 40% DP-60% SA.

The effect of feeding two different diets, containing 38 and 45% protein and 35 and 28% lipid, respectively, on growth as well as performance of the digestive proteases (total protease at pH 1·5, 7·0, 9·0 and 10·0) and carbohydrases (total carbohydrase, α‐amylase and α‐glucosidase) of a new candidate species for aquaculture, the carnivorous spotted wolffish Anarhichas minor (Teleostei, Anarhichadidae), was investigated. No significant growth differences were observed when feeding high protein (HP) or low protein (LP) levels ( P > 0·05), although the LP group exhibited slightly higher protease activity and capacity ( P > 0·05), mostly at the anterior end of the intestine and at alkaline pH. Carbohydrase levels were generally low, apart from α‐glucosidase, which was significantly increased for the HP group ( P < 0·05). Implications concerning the performance of digestive enzymes under varying dietary macronutrient levels and effects of digestive enzyme activity on the formulation of efficient artificial diets for carnivorous fishes are discussed in this study.

Digestive enzyme activity and capacity (activity x tissue weight) for protein (total protease assay, 25 degrees C) and carbohydrates (total carbohydrase and alpha-glucosidase assay at 5, 18 and 25 degrees C) was investigated for the carnivorous stargazer Uranoscopus scaber along its digestive tract. Results indicated that whole gut total protease activity was highest at pH 1.5 (P<0.05) (25 degrees C) in U. scaber (6.64 +/- 2.55 rug tyrosine per g digestive tract per minute, pH 1.5). Total protease activity was apparent mainly in the stomach at pH 1.5 (9.73 +/- 3.3), and to a lesser degree in the anterior intestine (11.15 +/- 1.5, pH 10.0) and pyloric caeca (4.92 +/- 2.06, pH 10.0), especially at pH 9.0 and 10.0. Furthermore, 60% of total capacity for protein digestion derives from the stomach region, which takes up 65% of the digestive tract. Total carbohydrase activity and capacity levels were very low compared to other carnivorous teleosts, indicating very low tendency for complex, large molecular weight carbohydrate digestion. However, alpha-glucosidase levels were higher, a fact which combined with relevant data for other marine carnivorous teleosts suggests a possible role of disaccharides in relation to marine carnivorous fish dietary carbohydrate inclusion.