Starvation before slaughtering as a tool to keep freshness attributes in gilthead sea bream (Sparus aurata)

Instrumental quality parameters related to freshness were evaluated for gilthead sea bream (Sparus aurata) after different storage periods on ice (2, 4, 7 and 11 days of storage) for one, four and eight days of pre-slaughter starvation. The study was carried out on 360 gilthead sea bream from five different groups reared on a commercial fish farm. Starvation period had a significant effect on fish texture: the force necessary to compress 4 mm of flesh after two days ice storage in 1 day starved fish (16.50 ± 0.59 Newtons) was less than that for four day (18.98 ± 0.63 Newtons) and eight day starved fish (20.43 ± 1.12 Newtons). Significant differences in flesh puncture and flesh compression were not detected, although these values did increase with increasing starvation period. A significant increase in pH and myofibrilar protein solubility was also detected for fish starved for one day.     

Stress assessment,quality indicators and shelf life of three aquaculture important marine fish,in relation to harvest practices,water temperature and slaughter method

The objective of this study was to evaluate the effect of harvest practices and slaughter method on stress, quality and shelf life of whole fish (gilthead sea bream, European sea bass and red sea bream) towards the development of a humane slaughter practice. The use of hook and line resulted in significantly lower plasma cortisol and glucose in European sea bass and gilthead sea bream. Water temperature at harvest affected significantly the concentrations of stress indicators (plasma cortisol and glucose), mainly in European sea bass and gilthead sea bream. No significant differences were observed between the harvesting methods, regarding fish appearance, microbial spoilage and sensory scoring and subsequently shelf life. However, significantly lower hardness was recorded in fish harvested using the electric stunner, compared to the fish killed with slurry ice of the same harvesting period. Shelf life ranged between 13–18 days for gilthead seabream, 10–16 days for European sea bass and 10–14 days for red sea bream, depending on harvesting period.     

Alterations in lipid metabolism and use of energy depots of gilthead sea bream (Sparus aurata) at low temperatures

Gilthead sea bream cultured along the northern Mediterranean coast are affected by the winter season when low temperatures reduce fish feed intake and growth. The coldest episodes can provoke a fish pathology known as ‘winter disease’. The effects of low temperatures, as well as concurrent fasting, have been studied by transferring three groups of gilthead sea bream from 16 °C to 14 °C, 12 °C and 8 °C. Fish at 12 °C and 8 °C refused food, whereas those at 14 °C were not fed following the temperature drop. Changes in body indices, organ composition, liver metabolism, and in particular, lipid fractions and their fatty acids were analysed on days 7 and 20 after the temperature shift. Only the rapid reduction of non-polar lipids in muscle was common for the three conditions. Fasting effects were linked to the maintenance temperature, being maximal after 20 days at 14 °C where fish body weight, hepatosomatic index, and perivisceral fat were reduced by 18%, 40%, and 60%, respectively. In this group, liver lipids did not change, as was the case for the enzymatic activities of liver glucose-6-phosphate and phosphogluconic acid dehydrogenases (G6PDH and PGADH) and lipoprotein lipase (LPL). In contrast, the liver of sea bream submitted to 8 °C accumulated large amounts of non-polar lipids (from 80 mg to 125 mg in 20 days), changing in size and aspect (bigger, pale, and friable). Simultaneously, liver LPL and hepatic lipase (HL) activities decreased. After 20 days at 8 °C, sea bream exhibited incipient acclimation responses to low temperatures: rising levels of unsaturation ratio in gill and liver polar lipids, of docosahexaenoic acid (DHA) in muscle polar lipids, and of G6PDH and PGADH hepatic activities.Fish at 12 °C presented some changes similar to those of the group at 14 °C (e.g., in morphological indices, and LPL and HL activities) and others like the group at 8 °C (increases in G6PDH and PGADH), suggesting a temperature threshold for gilthead sea bream (below 13 °C).     

Effects of additive iron on growth,tissue distribution,haematology and immunology of gilthead sea bream, <Emphasis Type="Italic">Sparus aurata</Emphasis>

The comparative effects of iron-supplemented levels on growth, tissue distribution, haematology and immunology of gilthead sea bream, Sparus aurata (2 g) were investigated, using four organic (50, 100, 200, 300 mg ORG/kg diet) and one inorganic iron source (200 INOR mg/kg diet). Fish were treated for 12 weeks with the experimental diets and maintained at a water temperature of 19–22°C. Growth (final weight and specific growth rate), tissue distribution (spleen, liver and muscle), haematological parameters (red blood cells, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration) and non-specific immune indexes (respiratory burst activity and antibacterial activity of serum) were analysed. No significant differences were found in growth and iron tissue distribution among the tested groups. Red blood cell counting was statistically higher in fish given 50 ORG, 100 ORG, 200 ORG and 200 INOR feeds. However, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration were not significantly affected by increasing dietary iron. Fish receiving the 100 ORG diet had the best performance with respect to the respiratory burst activity and significantly higher values for antibacterial activity of serum were obtained in fish fed with the 300 ORG diet. The present findings provided no clear evidence of the optimum iron concentration. However, there was adequate indication that iron supplementation enhanced the performance of gilthead sea bream, mainly from a haematological and immunological point of view.     

Impact of aquatic acoustic noise on oxidative status and some immune parameters in gilthead sea bream Sparus aurata (Linnaeus, 1758) juveniles

This study evaluated the ambient noise effect of onshore and offshore aquaculture systems on oxidative status and on some immune parameters in gilthead sea bream (Sparus aurata) juveniles. The experiment was performed for 40 days, projecting two different playlists of acoustic stimuli: offshore aquaculture noise condition that created the typical acoustic field in proximity of an offshore sea cage for fish farming, using a random sequence of quite sea background and boat noises; and onshore aquaculture noise condition that represented the acoustic field inside an open concrete tank for fish farming. A third group without any acoustic projection was used as a control. After 40 days from the beginning of acoustic noise, fish exposed to the offshore aquaculture condition showed significantly higher levels of total oxidant status, lysozyme activity, antiprotease activity and white blood cells together with a lower albumin/globulin ratio in comparison to fish from the control group; whereas fish exposed to the onshore condition showed analytical data placed between the other groups, though never significantly different. These results demonstrate that the offshore aquaculture noise, and in particular the sea soundscape, adversely influences the oxidative status and the immune function of gilthead sea bream determining a mild stress condition that could affect the sea bream welfare.     

Preliminary Results on Rearing of Sparus Aurata × Pagrus Pagrus Hybrids. Performance Comparison With the Parental Species

Hybridization between gilthead sea bream, Sparus aurata, and red porgy, Pagrus pagrus, was undertaken and viable hybrids were produced by an artificial hormonal-induced cross. The hybrids, from the cross of female red porgy and male gilthead sea bream (Pp × Sa), survived through the yolk-sac larval stage. The hybrids produced from the cross of female gilthead sea bream and male red porgy (Sa × Pp) presented higher mortality in the larval stage (98.4%) compared to gilthead sea bream (80.0%) and red porgy (92.5%). Afterwards, the Sa × Pp hybrid was compared to the offspring of its parental species under the same rearing conditions (tanks of 500 l capacity, natural light, ambient temperature, self-feeding with commercial feed) in a 40–week experiment. In this comparative study, the Sa × Pp hybrid had intermediate mortality rate (6%), compared to gilthead sea bream (0%) and red porgy (21%). The growth profile of this hybrid resembled the slow growing phases of its parents (red porgy in warm period and gilthead sea bream in cold period). The feed conversion ratio between fish forms was not significantly different (1.54–1.84 in the Sa × Pp hybrid, 1.53–1.56 in the maternal species and 1.33–1.40 in the paternal one). The body weight variation in the Sa × Pp hybrid was quite high (31.7–37.9%), compared to that in gilthead sea bream (19.7–24.7%) and red porgy (18.0–31.3%). With respect to body coloration, the Sa × Pp hybrid was distinguishable and classified into groups of red porgy-like (55.1%), gilthead sea bream-like (40.6%), and intermediate forms (4.3%). The preliminary results of this study proved that the produced Sa × Pp hybrid had too low a performance for aquaculture use, but the interesting consequent hereditary potential could be a useful tool in fish hybridization practice.     

Consumption of feeds containing the antibiotic sulfadiazine by gilthead sea bream (Sparus aurata,L.) and rainbow trout (Onchorynchus mykiss,Walbaum)

A method for studying the efficacy of sulfadiazine as a marker to estimate feed intake is presented. Feeding studies were carried out with two species, rainbow trout as a freshwater fish model and gilthead sea bream as a marine fish model, using two temperatures and two sizes of juveniles. The study showed the different feeding behaviour observed in both species, depending on the temperature and the number of days feeding the particles with sulfadiazine, and confirmed a dominant‐subordinate behaviour especially in the case of gilthead sea bream juveniles.     

Linseed oil inclusion in sea bream diets: effect on muscle quality and shelf life

Dietary lipid source in aquaculture has become a central topic in research whilst natural resources availability diminishes. Hence, to weigh up and forecast consumers impressions, the impact of partial (70%) and complete (100%) dietary replacement of fish oil (FO) by linseed oil (LO) on sensory and quality attributes was studied during the edible shelf life of gilthead sea bream (Sparus aurata). Physico‐chemical parameters (pH, torrymeter, total volatile basic nitrogen, thiobarbituric acid reactive substances and texture), and sensory analysis, both in cooked and raw fish were carried out during 17 days of ice storage. Throughout ice storage, feeding with LO diets, TBARS values remained lower on muscle than those found when feeding FO control diet. On freshly caught fish (day 0 of ice storage), statistically significant dietary texture variations were recorded on cooked fillet fed FO diet. No sensory differences on Quality Index Method, sensory profile or Torry scheme were found with partial or total LO replacement diets.     

Effects of Oil-in-Water Nanoemulsion Based on Sunflower Oil on the Quality of Farmed Sea Bass and Gilthead Sea Bream Stored at Chilled Temperature (2 ± 2°C)

The influence of oil-in-water nanoemulsion on the sensory, chemical, and microbiological qualities of sea bream and sea bass fillets stored at 2 ± 2°C was investigated. The results showed that the use of nanoemulsion extended the shelf life of fish one or two days when compared with the control. Treatment with nanoemulsion significantly (p < 0.05) decreased the values of chemical parameters throughout the storage period. Bacterial growth was inhibited by the use of nanoemulsion. Nanoemulsion had an inhibitory effect on protein denaturation during refrigerated storage and microwave cooking. Based on the results, it can be concluded that sunflower oil-based nanoemulsion extended the shelf life and improved the quality of both sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) fillets during storage.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

Effects of chronic confinement on physiological responses of juvenile gilthead sea bream, Sparus aurata L., to acute handling

Understanding how gilthead sea bream, Sparus aurata L., an important Mediterranean Sea species for aquaculture, respond physiologically to stressors commonly encountered in intensive rearing is important for effective production, as managing for stress is a major factor in maintaining healthy fish stocks. Our objective was to determine whether holding juvenile gilthead sea bream at a high density (HD), as a chronic stressor, would affect their physiological responses to a subsequent acute handling stressor. After acclimation at a low density (LD) of 6 kg m^?3 in 200‐L circular tanks containing 33–36 g L^?1 recirculating seawater at 19°C under a normal photoperiod, juvenile 37‐g gilthead sea bream were confined for 14 days at a HD of 26 kg m^?3 and then subjected to 30‐s aerial emersion in a dipnet. Plasma levels of cortisol, glucose, lactate, osmolality and chloride were determined in fish held in separate lots during LD (control) and HD confinement at 0, 1, 2, 7 and 14 days, and then after handling at 0, 1, 2, 4 and 8 h. Although plasma cortisol levels were similar in LD and HD fish groups after 14 d of confinement (15 and 23 ng mL^?1, respectively), the cortisol response in fish from the HD treatment at 1 and 2 h following acute handling (70 and 37 ng mL^?1, respectively) was only about half of that measured in the control group (139 and 102 ng mL^?1); plasma cortisol was similar in both groups by 4 and 8 h. In contrast, plasma glucose elevations in response to handling were higher at 4 and 8 h in the HD‐held fish (94 and 72 mg dL^?1, respectively) than in those from the LD treatment (59 and 51 mg dL^?1); glucose responses were similar in both groups at 1 and 2 h after handling and throughout confinement. Plasma lactate levels were higher in LD fish than in the HD group at the beginning of the experiment but were similar after 14 d confinement and responses to handling were similar (e.g. 33 and 35 mg dL^?1 at 1 h). Plasma osmolality showed increases during the first 2 h after acute handling but no differences were evident between the two density treatments at any time during confinement or posthandling. Plasma chloride levels did not change throughout the experiment. The reduced plasma cortisol response to acute handling likely resulted from negative feedback of mildly but chronically elevated circulating cortisol caused by the confinement stressor on the hypothalamic–pituitary–interrenal axis. While other post‐handling physiological changes also showed differences between treatment groups, the suppressed cortisol response in the HD‐held fish suggests a reduction in the gilthead sea bream's normal capacity to respond to an acute stressor.     

ORIGINS MATTER: (NO) MARKET INTEGRATION BETWEEN CULTURED AND WILD GILTHEAD SEA BREAM IN THE SPANISH SEAFOOD MARKET

Interactions between fisheries and aquaculture have become a major issue that is still insufficiently studied. Therefore, the objective of this article is to test whether the cultured and wild gilthead sea bream in the Spanish seafood markets are integrated. By using the Johansen methodology, cointegration of the price series of farmed and wild gilthead sea bream was tested. In contrast to previous studies, our econometric results show that wild and the farmed gilthead sea bream form two heterogeneous products in the Spanish market. These new results question the generalization currently accepted by the scientific literature that farmed and wild fish are substitutes when they belong to the same species. The binomial product-market, along with some specific features of the Spanish market, such as the negative perceptions of aquaculture by some significant groups of consumers, appeared to have a great explanatory power for justifying these different results.     

Effects of dietary mannan oligosaccharides in early weaning diets on growth,survival, fatty acid composition and gut morphology of gilthead sea bream (Sparus aurata,L.) larvae

Early weaning of marine fish larvae with dry diets delays gut maturation and reduces growth rates. In juvenile and adult forms of several marine fish species, inclusion of dietary mannan oligosaccharides (MOS) improves gut integrity and functionality, but the effects of MOS inclusion in gilthead sea bream (Sparus aurata, L.) larval diets have not been addressed yet. Thus, this study assesses the effects of dietary MOS inclusion on survival, growth performance, gut morphology, feed acceptance and quality of gilthead sea bream larvae. For that purpose, 16 days post‐hatched gilthead sea bream larvae were fed four graded levels of MOS (Biomos^®, Alltech, Nicholasville, KY, USA) in weaning diets as follows: 0 g kg^?1 MOS, 0.5 g kg^?1 MOS, 1.5 g kg^?1 MOS and 2 g kg^?1MOS. Dietary MOS did not affect feed acceptance in gilthead sea bream larvae (P > 0.05). MOS supplementation was correlated in a dose‐dependent way with higher larval survival (P = 0.026). After 15 days of feeding, dietary MOS increased whole larvae (P < 0.01) arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. Gilthead sea bream larvae fed 2 g kg^?1 MOS presented higher gut occupation with goblet cells after feeding compared with larvae fed the other dietary treatments. Overall, the results suggest that inclusion of MOS in early weaning diets for gilthead sea bream improves essential fatty acid utilization and may promote growth and final survival.     

Substrate-SDS-PAGE determination of protease activity through larval development in sea bream

Identification of alkaline proteases produced during larval stages of gilthead sea bream, Sparus aurata was achieved using SDS-PAGE and specific inhibitors. Such techniques were also applied to determine proteases existing in rotifers, Brachionus plicatilis, and Artemia nauplii, which are used as live food for these larvae, as well as proteases of adult fish. The results show a great prominence of trypsin-like proteases during the 4 weeks after hatching, but the number of enzyme species was reduced in adult fish. Alkaline proteases present in the rotifers and Artemia showed clear differences when compared with those of the larvae and were not detected in extracts obtained from fed larvae. The results obtained provide information about the role of exogenous enzymes in larval feeding of sea bream.     

Dietary supplementation with Mannanoligosaccharides (MOS) from Bio‐Mos enhances growth parameters and digestive capacity of gilthead sea bream (Sparus aurata)

Dietary mannanoligosaccharide (MOS) from commercial product, Bio‐Mos supplementation, has been examined for its effects on weight gain and feed conversion of domestic mammals and birds, but very few studies have evaluated the responses of aquacultural species to MOS. A feeding and digestibility trial was performed to asses the potential beneficial effect of two levels of Bio‐Mos on growth, feed utilization, survival rate and nutrients’ digestion of gilthead sea bream (Sparus aurata) with an initial average weight of 170 g. Bio‐Mos was added at 2 or 4 g kg^?1 to a fish meal–based control diet, and each diet was fed to triplicate groups of 1‐year‐old gilthead sea bream. After 12 weeks, there were no differences in survival rate among fish fed experimental diets (P > 0.05). It was observed that a significant improvability existed for both growth and feed utilization in fish fed diets supplemented with Bio‐Mos (P < 0.05). Body proximate composition remained unaffected by Bio‐Mos supplementation in fish fed experimental diets (P > 0.05). Apparent digestibility values for protein, carbohydrate and energy were appreciably affected by the inclusion of two different levels of Bio‐Mos, only lipid digestibility was the exception. In conclusion, the results of this trial indicate that 2 g kg^?1 dietary supplementation with BIO‐MOS seem to be most positive for gilthead sea bream production.     

Effects of low temperatures and fasting on hematology and plasma composition of gilthead sea bream (Sparus aurata)

Low temperatures, and the voluntary fasting that they induce, have been implicated in outbreaks of winter syndrome in farmed gilthead sea bream (Sparus aurata). Two experiments were performed with the objective of studying if a decrease in water temperature is sufficient to induce this disease or some of its associated signs. In the first experiment, water temperature was either acutely or gradually reduced to 8 °C. In the second experiment, fish were exposed to either 8 °C or 12 °C, or fasted at 14 °C. Although no mortalities due to winter syndrome were registered during any of the experiments, some of the signs described in affected sea bream were observed in 8 °C-exposed fish. Among the most relevant were the paleness and friability of the liver and the occurrence of fatty degeneration in the hepatocytes. During the experiments, the general state of health of fish was monitored by measuring hematic parameters and the plasma concentration of proteins, glucose and ions. Low temperatures (8 and 12 °C) and fasting at 14 °C resulted in significant decreases in the levels of the different plasma protein fractions. This drop was more important in all the 8 °C-exposed fish, due mainly to a higher descent of albumin, α₁-globulins and fibrinogen. Moreover, 8 °C-exposed fish showed a fall in total white blood cells and a rise of plasma glycemia, as well as a significant drop of plasma potassium and calcium levels and a transient increase of plasma magnesium concentration. In 8 °C-exposed fish, the rate of water temperature descent did not modify the profiles of change of any of the studied parameters. These results indicate that at 8 °C gilthead sea bream are unable to maintain the levels of plasma protein fractions and ions present in control animals. This revised version was published online in July 2006 with corrections to the Cover Date.     

Predicting the growth of gilthead sea bream (Sparus aurata L.) farmed in marine cages under real production conditions using temperature- and time-dependent models

The growth of gilthead sea bream ( Sparus aurata ) has been studied considering five multiple exponential regression models using data from 20 lots of gilthead sea bream growing in 20 marine cages from a Mediterranean commercial fish farm. The final weight ( W _f) of fish was predicted in relation to the initial weight ( W _i), time ( n ) and temperature ( T ), or the sum of effective temperatures (∑ T _ef). The estimated weight results from the simulation using the five models have been compared with the real final weight values using the mean of the absolute values of the prediction errors in short and long term (the precision value). All models presented a high determination coefficient, above 96%, and good prediction values in the short term. Regression models were tested using data from six new cages. The best models for predicting the growth of sea bream long term were the ones where final weight is expressed in relation to the initial weight and the sum of effective temperature,     and     obtaining long-term prediction errors 12.9% and 10.7% respectively.     

Effects of dietary soybean oil concentration on growth, nutrient utilization and muscle fatty acid composition of gilthead sea bream (Sparus aurata L.)

A 309 days feeding experiment was carried out on gilthead sea bream fingerlings (initial weight 14.7±4.4 g) to evaluate effects of substitution of fish oil with soybean oil in diets on growth and sensory characteristics and muscle fatty acid composition. Duplicate groups of fish were hand fed with four isoenergetic and isonitrogenous diets (46% protein, 14% lipid and 22 MJ kg⁻¹) in which 0%, 24%, 48% or 72% of the fish oil was replaced by soybean oil. Fish fed diet 72% reached a lower final weight (324 g) than fish fed diets 0%, 24% and 48% (349, 343 and 338 g respectively). Feed intake, protein efficiency ratio, body composition and economic profitability were not influenced by the amount of soybean oil in the diets, but muscle fatty acid composition differed with diets. Panellists observed significant sensory differences between fish fed diet 0% and diet 72%. These results verified the possibility of feeding sea bream until they reached commercial weight with a 48% dietary substitution of fish oil for soybean oil.     

Effect of high-level fish meal replacement by plant proteins in gilthead sea bream (Sparus aurata) on growth and body/fillet quality traits

Juvenile gilthead sea bream (initial body weight ca. 100 g) were reared in an indoor flow through marine water system for 1 year. Fish were fed two isoenergetic [19.2 kJ g⁻¹ dry matter (DM)] and isoproteic (426 g kg⁻¹ DM) diets either based on fish meal (diet FM) or on a mixture of plant protein sources (diet PP), replacing 75% of fish meal protein. The growth trial was conducted in duplicate, two tanks for each dietary treatment. Growth performance and feed utilization were registered. Fillet quality parameters were evaluated and sensory analyses on cooked fillet were performed. Both groups had similar weight gain and specific growth rates. Feed intake was higher in sea bream fed diet FM (0.48 versus 0.44), while feed efficiency and protein efficiency ratio were significantly higher in sea bream fed PP (0.83 versus 0.77 and 2.0 versus 1.76, respectively). Sea bream fed diet FM had a lower hepatosomatic index (0.80 versus 0.87%), and a higher fillet yield (45.9 versus 44.9%). The fillet from sea bream fed diet FM had higher moisture (696 versus 682 g kg⁻¹), lower lipid levels (91 versus 100 g kg⁻¹) with higher levels of n‐3 polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA), while the PP fed sea bream presented a higher level of PUFA n‐6. There were minor differences in muscle free amino acid levels between the two diet groups. As regards sensory evaluation of cooked fillet, the judges were unable to discriminate the two dietary groups of fish. Summarizing, the results demonstrate the possibility to use diets containing high levels (750 g kg⁻¹) of plant ingredients in gilthead sea bream without affecting growth performance and with minor effects on quality traits of commercial size sea bream.