The effects of a temperature rise on oxygen consumption and energy budget in gilthead sea bream

The rates of daily average, minimum and maximum oxygen consumption, specific dynamic action (SDA), ingestion and digestibility in gilthead sea bream, Sparus auratus L., were measured before, during and after a gradual rise of water temperature from 20 to 28 °C at a rate of 1 °C day-1. The relationship between energy gain and the metabolic costs has also been investigated. Oxygen consumption of juvenile sea bream had a clear daily rhythmicity, with low levels during darkness and higher levels during the light period. Both light and feeding processes raised the metabolism of sea bream, but fish fasted for 2 days also showed an increase in oxygen consumption during the light period. Acclimation to 28 °C was complete for the minimum oxygen consumption rate in 12 days, but daily average and maximum oxygen consumption rates on the 19th day after the change were still 33% higher than at 20 °C mainly due to increased SDA. The digestibility of food components did not change significantly throughout the experiment. These relationships are discussed with respect to the potential for growth when fish are reared at 28 °C, although the energy costs are high.     

The effect of demand feeding on swimming speed and feeding responses in Atlantic salmon Salmo salar L., gilthead sea bream Sparus aurata L. and European sea bass Dicentrarchus labrax L. in sea cages

Abstract Using underwater cameras, data were collected on the feeding behaviour and swimming speeds of Atlantic salmon Salmo salar L., gilthead sea bream Sparus aurata L. and European sea bass Dicentrarchus labrax L. in sea cages. Comparisons were made between the behaviours of fish fed on demand using interactive feedback systems and those of fish fed under the standard feeding practice of each farm (control). In all three species, swimming speeds were similar before feeding , but they were significantly higher in the control regimes during feeding. When fed on demand, sea bass had reduced swimming speed just before and during feeding compared with that observed during the non‐feeding periods. Higher proportions of feeding fish were observed in the control regime cages than in fish fed on demand for all three species, indicating a greater feeding intensity during meals in the control regimes. This was further supported by observations of an increase in the density of sea bass in the upper water in the control cages during feeding. The results suggest decreased levels of competition between the on demand‐fed fish during feeding, which might be hypothesized to lead to improved growth and production efficiency in aquaculture.     

Diel changes in plasma cortisol and effects of size and stress duration on the cortisol response in European sea bass (Dicentrarchus labrax)

European sea bass (Dicentrarchus labrax), one of the most economically important fish in Mediterranean mariculture, shows high basal cortisol concentrations compared with other teleosts. The present study aims (a) to identify cortisol diel variation in fish held under a 12L:12D cycle and minimum handling stress, and (b) to establish the effect of fish size and stressor duration on the cortisol response. The results indicate high intrapopulation variability in plasma cortisol and a significant diel fluctuation with a peak value at dusk (18 h). Stressors of different intensity and/or duration affected the cortisol stress response in a differential manner according to fish size (and/or age). Maximum cortisol values in small-size fish were found at 1 and 2 h post-stress, depending on the duration of the stressor, while at 0.5 h post-stress in large fish regardless stress duration.     

Protein sparing effect of dietary lipids in common dentex (Dentex dentex): A comparative study with sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

The common dentex (Dentex dentex) is a sparid fish which is considered a suitable candidate for Mediterranean aqua-culture. A seven-weeks feeding trial was conducted over the summer period with common dentex, sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). All three species were fed to visual satiety with two practical diets with varying crude protein and crude fat levels (55 % protein, 9 % lipids; 46 % protein, 17 % lipids). The initial body weights were 8.2, 11.6 and 17.3 g for common dentex, sea bass and sea bream, respectively. In all cases, specific growth rates were not significantly affected by dietary treatment, but they varied among species (sea bass 1.7–1.8 %; sea bream 2.1–2.3 %; common dentex 3.1–3.2 %). When comparisons between fish species were made, we observed that the increase in growth rates was linked to a decrease of the whole body fat content, as a consequence of a greater utilisation of dietary lipids as energy substrates. Furthermore, in common dentex, the 17 % lipid diet was able to improve protein retention, but this diet effect was less significant in sea bream and sea bass. In contrast to sea bream, the 17 % lipid diet did not up-regulate plasma GH levels in common dentex, which provides additional evidence for a more efficient utilisation of dietary lipids.     

Diel Rhythms of Serum Metabolites and Thyroid Hormones in Red Porgy Held in Different Photoperiod Regimes

Diel rhythms in serum glucose, lactate, cholesterol, triglycerides and thyroid hormones were studied in red porgy, Pagrus pagrus, held under different photoperiod regimes (constant darkness – DD, 8L:16D,12L:12D), at a constant temperature (17.1–18.7 °C) and fed with commercial pellets, by means of a self-feeder. A clear diurnal rhythm in feeding activity, regardless of the photoperiod regime was demonstrated. All serum components showed significant diel rhythms, although they were not necessarily consistent or circadian in periodicity. As well as this, differences in the average values among the varying treatments were observed. Fish held under the 12L:12D protocol displayed significantly higher average T₄, T₃ and lactate levels during the day rather than at night. Maximum glucose values occurred 8–12 h after dawn and maximum lactate concentrations at 06:00 or 14:00 h. Diel variations in cholesterol were evident only in the DD group with peak values inversely correlated with the rhythm of food intake. Triglycerides displayed a similar pattern of changes. Significant diel fluctuations in T₄ serum levels were observed only in fish exposed to the 12L:12D protocol, with peak values at dawn. A clear diurnal peak (10:00 h) in T₃ concentrations was observed in fish subjected to the 12L:12D regime, while fish exposed to the 8L:16D protocol showed two peaks: one in the photophase (10:00 h) and another in the scotophase (02:00 h). The light–dark alternation and the general activity rhythm of fish seem to be the main synchronizers of the diel rhythms observed in this study.     

Post-haemorrhagic anaemia in sea bass,Dicentrarchus labrax (L.), caused by blood feeding of Ceratothoa oestroides (Isopoda: Cymothoidae)

The effects of the fish parasitic isopod, Ceratothoa oestroides (Risso), on haematological parameters of its cage-cultured sea bass host, Dicentrarchus labrax (L.), were studied. Analyses of blood parameters (cell counts, haemoglobin content and haematocrit) were carried out on parasitized and unparasitized sea bass from a fish farm in Turkey. Parasitized fish had significantly lowered erythrocyte counts, haematocrit and haemoglobin values and significantly increased leucocyte counts. Blood feeding by C. oestroides thus produces a post-haemorrhagic anaemia and the fish appear to mount an immune response to the presence of parasites.     

Recent advances in European sea bass and gilthead sea bream nutrition

European sea bass (Dicentrarchus labrax) and gilthead sea bream(Sparus aurata) are amongst the most important finfish speciescultured in the Mediterranean region. Production of these species isnowadays a well-controlled process, but knowledge of their nutritionalrequirements is still very limited. Nevertheless, a considerable amountof data has been accumulated in recent years, and the purpose of thispaper is to review the recent advances on the nutritional requirementsof sea bass and sea bream. The optimum protein to energy ratio of thediets of sea bass and sea bream seem to be higher than for salmonids,and there is some evidence that high dietary lipid levels have nobeneficial effects on fish performances. Although the essential aminoacid requirements were estimated by the ideal protein method, data basedon the dose-response method is only available for a few amino acids.Essential fatty acid requirements were estimated for sea bream juvenilesbut data is lacking for sea bass. Vitamin and mineral requirements ofthese species are practically unknown. Although the importance ofbroodstock nutrition on gonadal development, spawning and egg quality isrecognized, few studies were done to elucidate these aspects. The recentdevelopment of microparticulate diets for larvae will contribute to theaccurate evaluation of their nutritional requirements.     

Gastric evacuation and feeding in the gilthead sea bream reared under semi-intensive conditions

Gastric evacuation rates of the gilthead sea bream, Sparus aurata, fed with commercial pelleted food and polychaetes (Nereis diversicolor) were determined under experimental conditions. The estimated gastric evacuation rate for pelleted food was 7.97% h^–1, with a total time of digestion of approximately 9 h. The respective values for the natural food were 6.24% h^–1, with a total digestion time of approximately 12 h. The daily consumption of fish reared in earth ponds in a semi-intensive aquaculture facility was estimated through 24 h cycles performed between April and August. The daily consumption varied from 18.58 to 31.98 mg g^–1. There was a constant increase in the average daily consumption per individual of 1.8–4.6 g (dry weight). During these cycles, samples of stomachs were taken and the contents preserved for further observation. The feeding behaviour of the reared fish was compared with a fish sample caught in the Ria Formosa lagoon. No common species were found between samples. A total of 38 prey were identified, which suggests that the gilthead sea bream is a non-specific predator. Despite the high abundance of natural prey in the ponds, the dependence of sea bream on pelleted food was high.     

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.     

Competition between farmed and wild fish: The French sea bass and sea bream markets

ABSTRACT

Aquaculture is contributing at an increasing rate to the world seafood supply. The interaction between fisheries and aquaculture is especially important for the seafood market where supply of wild and farmed fish can affect price dynamics. We examine market interactions in the French fresh sea bass and sea bream markets. We test for long-term price parity between farmed and wild products for these two species, applying a bivariate cointegration approach to market delineation. We also conduct the Law of One Price (LOP) test between price series. Our data base consists of monthly domestic price series for fish purchased by French households from 2007 to 2012. Our empirical results show that the fresh fish markets for whole wild and farmed sea bream are partially integrated, yet those for whole wild and farmed sea bass are not integrated. The substantially higher price for wild sea bass relative to farmed sea bass suggests that consumers may be more sensitive to seafood production processes when it comes to higher-value species.     

Diurnal changes of dissolved oxygen in fouling land-based tanks for rearing of sea bass

Concentration of dissolved oxygen (DO) was measured in non-fouling tanks with sea bass and in fouling tanks without fish. The rate of oxygen production and respiration of fouling organisms and the rate of oxygen consumption by sea bass were calculated from the changes of DO. It was possible to approximate diurnal changes of these rates as periodical functions of time. A mathematical model was used to study the effects of fouling, density of fish and water flow on DO during the day (0–24 h). During the sunlight the fouling increases DO in the tank, while during the night it does not affect DO significantly. Water detention time significantly affects the minimum values of DO, and relatively little the maximum ones during the day.     

Price interactions between wild and farmed products: Turkish sea bass and sea bream markets

We investigate empirically market interactions in the Turkish wild and farmed sea bass and sea bream markets. For gilthead sea bream and European sea bass, we conduct a Granger causality test between the prices of the wild and farmed products, based on the estimation of a vector autoregressive model. Our data set consists of annual fish prices from 1996 to 2016. Our empirical results show that the wild and farmed sea bass are neither substitutes nor complements: the markets for each product are independent. However, in the case of sea bream, the price variations for farmed sea bream have a causal impact on the price of wild sea bream. Moreover, the price of wild sea bream Granger-causes the price variation of farmed sea bream. Thus, the wild and farmed sea bream markets are integrated.     

Diel feeding rhythms of greenback flounder Rhombosolea tapirina (Günther 1862): the role of light–dark cycles and food deprivation

The role of light–dark (LD) cycles and food deprivation in the regulation of diel feeding rhythms in greenback flounder Rhombosolea tapirina (Günther 1862) was examined. A computerized monitoring system was developed to record uneaten pellets, and food intake was estimated as the difference between pellets presented and those uneaten. Three groups of five fish each (75–281 g) were exposed sequentially to the LD cycles: LD 12:12, LD 12:12 (scotophase advanced by 9 h), LD 6:18, DD, LD 6:6:6:6, LL and LD 12:12 (return to the initial cycle). Illumination was 120 lux at the water surface (complete darkness at scotophase), and water temperature was 15 ± 1 °C. Fish fed mainly during the light hours under LD 12:12 and resynchronized to the scotophase-advanced LD 12:12 regime after about 12 h. Feeding started at the onset of light and extended to the early scotophase under LD 6:18. A circadian feeding rhythm was detected in fish under DD and LD 6:6:6:6 regimes. Under the LL regime, two groups of fish displayed arrhythmic feeding patterns and did not resynchronize to LD 12:12 for at least 13 days. In contrast, the third group of fish exhibited a circadian feeding rhythm under the LL regime and immediately re-entrained to LD 12:12. Fish were deprived of food for a single period of 26–57 h once feeding patterns had been established under LD 12:12, LD 12 : 12 (scotophase advanced by 9 h) and DD regimes, and feed delivery was resumed during the scotophase or subjective night; the timing of feeding rhythms was shifted by the reintroduction of feed, but progressively resynchronized to the LD cycles. The results suggest that the greenback flounder is a diurnal feeder, that a LD 12:12 cycle is a potent environmental cue to entrain circadian feeding rhythms, and that a biological clock is involved in the timing of feeding.     

Nocturnal feeding reduces sea bass (Dicentrarchus labrax, L.) pellet-catching ability

European sea bass exhibits a feeding rhythm with seasonal phase inversions: nocturnal feeding is predominant in winter, and diurnal feeding during the rest of the year. This explains the increased growth of sea bass fed at night during the winter months, but to fully assess such feeding practices, it is important to monitor food-catching efficiency in the dark. To evaluate the influence of nocturnal feeding on pellet-capture efficiency under laboratory conditions, we developed an infrared pellet detector linked to on-line recording with a microcomputer. Feed waste was recorded for eight groups of four sea bass (54.6±15.8 g body weight) fed either diurnal or nocturnal meals with long (>60 s) or short (<20 s) feed availability times. With short feed availability times, food-catching efficiency in complete darkness (0 lx) was reduced to 78.6%, compared to 93.5% in diurnally fed fish. This was confirmed in a second experiment, performed during winter, involving 4000 sea bass in four sea cages (1000 per cage) provided with self-feeders and pellets detectors. Feed waste amounted to less than 13% of the food distributed, but nocturnal demands (29% of total feed demands) were accompanied by higher levels of uneaten pellets (68% of the total feed waste) than diurnal demand. This suggests that if the aim is to reduce feed waste, nocturnal feeding should be restricted in sea cages.     

Seagrass habitat reduces vulnerability of red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis> juveniles to piscivorous fish predator

ABSTRACT:   Predation experiments were conducted in mesocosms to test the hypothesis that habitat complexity affects vulnerability of red sea bream Pagrus major juveniles to piscivorous fish predators. Juvenile behavior was video-recorded for 6 h in two structurally different habitats: vegetated with sea grass Zostera marina , and unvegetated 0.5-t tanks. Association behavior with seagrass was observed in the vegetated tank throughout the trials. Predation experiments were conducted with 30 red sea bream juveniles (29.9 mm body length) exposed to two individuals of the piscivorous fish predator Chinese sea bass Lateolabrax sp. (261.6 mm), for 6 h in 1.0-t tanks. Predation rate (no. of fish predated on per predator per h) was significantly lower in the vegetated tank (0.02/predator per h) than in the unvegetated tank (0.27/predator per h). Present experiments indicate that habitat complexity reduces vulnerability of juvenile red sea bream to predation by piscivorous fish by serving as physical and/or visual barriers and limiting the predator's ability to pursue and capture prey. Seagrass beds in the shallow coastal waters around Japan are suggested to be an important nursery for red sea bream since they provide the juveniles with habitat complexity as well as serve as a feeding ground.     

Ascorbate dynamics in embryos and larvae of sea bass and sea bream, originating from broodstocks fed supplements of ascorbic acid

The transfer of L-ascorbic acid (AA) from broodstock to the fertilised eggs and it's dynamics in embryos and fasting larvae, has been studied in sea bass (Dicentrarchus labrax L.) and sea bream (Sparus aurata L.). Two types of diets were fed to the broodstocks: one containing sufficient ascorbate for normal growth and the other with an extra addition of a very high dose (2,000 mg/kg feed) of ethyl-cellulose-coated L-ascorbic acid.The concentration of AA and total ascorbate (L-ascorbic acid plus dehydroascorbic acid) was detected through several embryo and larval development stages, including larvae just before feeding. In sea bass and sea bream, the mean (SD) concentration of total ascorbate in fertilised eggs originating from broodstock fed AA supplemented diet, was 218.5 (17.7) and 122.4 (5.1) g/g wet weight respectively. This was significantly higher (P < 0.01) than the unsupplemented groups, which contained only 155.9 (6.9) and 103.9 (3.5) g/g wet weight respectively. A diet with a vitamin C content adequate for normal growth, may not be sufficient for broodstock when the goal is transfer of TAA to embryos. © Rapid Science Ltd. 1998     

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.     

Physiological stress and innate immune response in gilthead sea bream (<Emphasis Type="Italic">Sparus aurata)</Emphasis> and sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>) exposed to combination of trimethoprim and sulfamethoxazole (TMP-SMX)

The purpose of this study was to determine whether gilthead sea bream and sea bass treated with combination of trimethoprim and sulfamethoxazole (TMP-SMX) differed in terms of physiological and innate immune biomarkers. Fish were exposed to TMP-SMX at 40 ppm concentration for 1 h as a prophylactic usage. Plasma cortisol, glucose, electrolytes (Ca, P, Na, K, Cl, and Mg) as well as plasma lysozyme activity, C-reactive protein (CRP), and ceruloplasmin (Cp) were measured soon after treatment and following 24 and 48 h in normal sea water for recovery. Treatment with TMP-SMX in both gilthead sea bream and sea bass led to an increase in plasma cortisol and glucose. Fluctuations in some electrolytes were found after treatment and during recovery period, however, the ratios of monovalent ions in treated sea bream were similar to control. Hematocrit values as well as plasma lysozyme activity in gilthead sea bream and sea bass were not affected by the treatment. CRP in gilthead sea bream and Cp in sea bass responded to the treatment with decreased levels. Both gilthead sea bream and sea bass displayed a rapid physiological stress response and sensitivity to TMP-SMX exposure, which requires more than 48-h period for regaining homeostasis.     

Demand-feeding behaviour of sea bass kept in ponds: diel and seasonal patterns,and influences of environmental factors

Feeding activity was investigated from June to October in a group of 60 sea bass, Dicentrachus labrax. The fish were kept in an earthen pond in a maritime wetland subject to the fluctuations of the natural environment. The fish fed by operating a demand feeder connected to a data logger which recorded each feeding act with a time reference. Meteorological and hydrological data were also recorded. Diurnal rhythms in feeding activity changed as the months progressed. Fish fed during daylight, preferentially at dawn in June, but in the middle of the day from August to October. Most feeding took place during subdued light. Feeding was closely and positively correlated to both daylength and water temperature; daylength being the most related factor associated with rainfall and East-West wind direction.