Sharpsnout Seabream Research Articles

Locomotor, feeding and melatonin daily rhythms in sharpsnout seabream ( Diplodus puntazzo)

Sharpsnout seabream is a marine teleost of increasing interest for Mediterranean aquaculture, but there is still a lack of information regarding its circadian organization. In this study, we have investigated sharpsnout seabream locomotor activity, feeding and plasma melatonin daily rhythms under a 12:12-h LD cycle, as well as the persistence of locomotor activity circadian rhythmicity under constant light (LL) conditions. When submitted to an LD cycle, most sharpsnout seabream displayed a diurnal locomotor pattern, with an average 74% of activity recorded during daytime. However, along the experiment 40% of fish spontaneously changed their locomotor rhythm phasing and became nocturnal. Feeding behaviour, nevertheless, remained strictly diurnal in all cases, with 97% of food demands being made during the light period. Free-running locomotor rhythms were recorded in one third of the fish kept under LL. Daily plasma melatonin levels displayed a rhythmic profile, with low daytime values (111 pg/ml) and high nighttime concentrations (791 pg/ml). Taken together, these results evidence a high degree of plasticity for sharpsnout seabream activity patterns, as well as phasing independence of locomotor and feeding rhythms. Finally, the existence of a well-defined daily rhythm of plasma melatonin was found.

Shape ontogeny and variation in the sharpsnout seabream, Diplodus puntazzo (Cetti 1777)

Shape ontogeny of Diplodus puntazzo was studied during the larval and metamorphosis phase (2.6–33.0 mm total length (TL)) by means of geometric morphometrics. Additionally, shape comparison was performed between newly settled wild individuals of D. puntazzo (11.0–18.0 mm TL) and reared of the same TL range. Results clearly demonstrated that shape ontogeny of D. puntazzo is not continuous during the studied period, but it is characterized by the presence of two inflection points (at 6.2 and 11.4 mm TL), which define three phases of significantly different rates of shape development (P<0.05). Spline diagrams demonstrated that shape ontogeny mainly correlated with the development of fins, caudal peduncle, snoot and the ventral abdominal profile. Concerning the comparison of reared fish with wild fish, morphometric analysis revealed a significant effect of fish origin on the shape of D. puntazzo (Wilks' λ=0.147, P<0.001). Shape differences between the two populations were mainly demonstrated at the caudal peduncle and at the ventral profile of the abdominal area. Combined with the results of shape ontogeny, spline diagrams showed that shape differences between the two populations were related to the comparatively more advanced ontogenetic state of reared fish, at the studied size range.

Seagrass ( Posidonia oceanica) vertical growth as an early indicator of fish farm-derived stress

The usefulness of vertical rhizome growth as an early indicator of fish farm impacts to Posidonia oceanica meadows was tested by comparing annual estimates of vertical rhizome growth, quantified retrospectively, at distances ranging between 5 and 1200 m from fish cages at four Mediterranean locations (Cyprus, Greece, Italy and Spain). The studied fish farms had been operating since, at least, 1997, producing between 150 and 1150 tons yr −1 of sea bream ( Sparus aurata) and sea bass ( Dicentrachus labrax), and, at Italy, also sharpsnout sea bream ( Diplodus puntazzo). The reconstructed vertical rhizome growth spanned from 19 to 25 years of growth, depending on sites, and the average vertical rhizome growth before the onset of fish farm operations ranged between 4.48 and 8.79 mm yr −1. The vertical rhizome growth after the onset of farming activities declined significantly ( t-test, P < 0.05) from the control station (at >800 m from the farm; vertical growth rate averaged 6.79, 5.52, 3.89 and 3.70 mm yr −1 at Cyprus, Greece, Italy and Spain control stations, respectively) to the impacted one (at 5–300 m from the farm; vertical growth rate was 4.82, 3.52, 2.77 and 1.92 mm yr −1 at Cyprus, Greece, Italy and Spain impacted stations, respectively) at each farm. Moreover, vertical growth significantly ( t-test, P < 0.05) declined by about twofold following the onset of fish farm operations for the extant meadow nearest to the cages, as well as those supporting intermediate impacts at distances 35–400 m from the cages. Vertical rhizome growth was not significantly affected after the onset of fish farm operations for the meadows located more than 800 m from the farm, except in those from the Italian site, the largest farm. Examination of the time course of vertical growth for individual rhizomes in the areas of the meadow nearest to the farms, except for those at Cyprus, showed that the decline in vertical growth was initiated within the year of the onset of farming activities, suggesting a negligible resistance of seagrass meadows to fish farm impacts. The results obtained confirm that fish farm activities strongly affect seagrass health on the surrounding meadows, and clearly demonstrate the value of reductions in vertical rhizome growth as an early warning symptom of stress and impacts to P. oceanica meadows.

Efficacy and toxicity of orally administrated anti-coccidial drug treatment on Enteromyxum leei infections in sharpsnout seabream (Diplodus puntazzo C.)

Three drugs effective against myxosporeans and commonly used to treat spore-forming para- sites were tested in sharpsnout sea bream (Diplodus puntazzo) infected by Enteromyxum leei. Two medicated diets were applied, one containing salinomycin and amprolium and the second containing fumagillin. Compared to untreated fish, both treatments resulted in significant reduc- tions in prevalence, intensity of all developmental myxosporean stages, and mortality. The effect was more prominent with the salinomycin and amprolium combination, where the significant reductions in intensity, prevalence, and mortality were unaccompanied by any histopathological evidence of toxic side effects or growth reduction. Sporoblasts and mature spores with distorted structures were observed in both drug treatments, but were more prevalent in the salinomycin and amprolium treatment than in the fumagillin treatment, indicating direct effectiveness on the parasite. Salinomycin with amprolium is a promising treatment for myxosporean infections in intensively cultured warmwater fish, leading to parasite elimination.

Antiparasitic and immunomodulatory effect of innovative treatments against Myxobolus sp. infection in Diplodus puntazzo

The potential antiparasitic and immunomodulatory effect of three treatments against myxosporean parasites on the innate immune system of sharpsnout sea bream ( Diplodus puntazzo) was investigated. Fish naturally infected with Myxobolus sp. (Bivalvulida/Platysporina), a histozoic parasite mainly affecting the renal interstitial tissue, were treated by oral administration of a combination of salinomycin with amprolium, Origanum essential oil or fumagillin in a small-scale field trial. Various leucocyte functions influenced by myxosporean infection were examined in order to determine treatment effects on leucocyte immunocompetence of treated fish. One month post treatment all drugs caused a significant decrease in prevalence and intensity of infection in comparison to untreated, infected fish. The effect was most prominent in salinomycin with amprolium treated fish, which 1-month post treatment contained either no cysts at all or a few spores free in melanomacrophage centres revealing almost total elimination of the parasite and the antiparasitic action of the treatment. There was no histopathological evidence of drug toxicity. Antiparasitic action was accompanied by a significant enhancement of phagocytic activity demonstrated by ingestion of large numbers of latex beads and the secretion of high levels of reactive nitrogen intermediates by phagocytes in vitro. Complete restoration of the diminished mitogenic responses and serum lysozyme secretion was also detected in salinomycin with amprolium-treated fish compared to untreated, infected fish. These data suggest that salilomycin with amprolium may be a promising treatment for myxosporean infections in intensively cultured warm-water fish, exhibiting action partially via the enhancement of host, innate immune functions and leading to parasite elimination.

Efficacy of 2-phenoxyethanol as an anaesthetic for two size classes of white sea bream, Diplodus sargus L., and sharp snout sea bream, Diplodus puntazzo C.

The objective of this study was to evaluate the efficacy of 2-phenoxyethanol as an anaesthetic for two size classes of white sea bream, Diplodus sargus L. (30 and 60 g), and sharp snout sea bream, Diplodus puntazzo C., (15 and 30 g) and establish the minimum concentration producing desirable anaesthetic effects on them. Fish were exposed to concentrations varying from 0.1 to 0.4 mL/L for a 60-min period. At concentrations of 0.1, 0.117 and 0.133 mL/L, 2-phenoxyethanol failed to induce anaesthesia, whereas at concentrations of 0.167, 0.2, 0.3 and 0.4 mL/L all the fish were anaesthetised within 3 min of exposure. However, mortality was observed with the two higher concentrations. Induction time decreased and recovery time increased with increasing concentrations, being significantly concentration-dependent in both species ( P ≤ 0.01). Following exposure of D. sargus to concentrations of 0.2 or 0.3 mL/L, both induction and recovery time were significantly weight-dependent ( P ≤ 0.01). However, erratic weight dependencies of both induction and recovery time were observed in D. puntazzo. 2-Phenoxyethanol proved to be an effective and safe anaesthetic in both species permitting rapid and uneventful induction and recovery after a 60-min exposure period. The minimum concentration producing desirable anaesthetic effects was 0.167 mL/L.

Dietary self-selection in sharpsnout seabream ( Diplodus puntazzo) fed paired macronutrient feeds and challenged with protein dilution

Macronutrient selection and responses to dietary protein dilution were investigated in 95-g sharpsnout seabream, an omnivorous fish species of interest for Mediterranean aquaculture. Five groups of 18 sharpsnout seabream were distributed among circular 450-l tanks and allowed to self-feed from 3 feeders each of which distributed feeds composed of different pairs of macronutrients: PC (75% protein, 25% carbohydrate), PF (75% protein, 25% fat) or FC (50% fat, 50% digestible carbohydrate). Regardless of self-feeders position, the fish composed a diet containing 63% protein, 19% fat and 18% carbohydrate. When the protein-containing diets (PC and PF) were diluted 50% with cellulose, the fish increased their food intake to compensate for the energy dilution (170 kJ/kg BW/day vs. 168 kJ/kg BW/day after dilution), and dietary composition (63% protein, 16% fat and 21% carbohydrate) did not change significantly. These results demonstrate that sharpsnout seabream can select from incomplete diets to compose a balanced diet, and the fish are also able to compensate for a dietary dilution to regulate both energy intake and the relative proportions of macronutrients.

The shape of the lipid vesicle is a potential marker for egg quality determination in the gilthead seabream, Sparus aurata, and in the sharpsnout seabream, Diplodus puntazzo

This study investigated whether morphological parameters measured in eggs during early embryonic stages (first cleavage to morula) were useful for prediction of egg quality (% hatching embryos out of floating eggs) in Sparus aurata and Diplodus puntazzo. Eggs obtained from natural spawning were collected from commercial broodstocks. In the viable, floating eggs, the minimal and maximal diameter of the egg, yolk, and lipid vesicle were measured. Based on these measurements several parameters were calculated describing the shape of the egg, yolk, and lipid vesicle, and the size relationship between these compartments. These parameters were investigated for correlation with egg viability. From all investigated morphometric parameters only the ratio of the maximal to the minimal diameter of the lipid vesicle (RDLV) and the lipid vesicle shape coefficient (LVSC) were correlated with larval survival (%) from viable eggs. As the shape of a lipid droplet depends on the type and composition of lipid, the lipid to water ratio, and the interactions with the surrounding water molecules this parameter may be an index for the biochemical lipid composition.

Determination of Embryonic Development Stages of Sharpsnout Seabream (Diplodus puntazzo Cetti, 1777) Eggs in Rearing Conditions

Determination of Embryonic Development Stages of Sharpsnout Seabream (Diplodus puntazzo Cetti, 1777) Eggs in Rearing Conditions

Effect of temperature on embryonic development in sharpsnout seabream (Diplodus puntazzo) eggs

Embryonic development of sharpsnout seabream (Diplodus puntazzo) was studied at eleven water temperatures (two degree intervals from 12 to 32°C). Embryos successfully developed at temperatures of 16-28°C. Cells did not divide at the temperature extremes of 12 and 32°C. Total mortality was observed by the 128 cleavage stage at 14°C and all eggs were dead by the time the embryos extended 2/3 of the internal circumference of the egg at 30°C. There was an inverse relationship between incubation temperature and the rate of embryonic development.

The effects of oxygen levels on oxygen consumption, survival and ventilatory frequency of sharpsnout sea bream (Diplodus puntazzo Gmelin, 1789) at different conditions of temperature and fish weight

Summary The respiratory behaviour of the sharpsnout sea bream (Diplodus puntazzo) with fish weights between 15 and 509 g at temperatures of 15–29°C was studied, with special attention paid to critical and lethal oxygen saturation (Scrit and LC50, respectively) and ventilatory frequency (Vf). The species maintained a constant oxygen consumption rate regardless of the concentration of dissolved oxygen, until Scrit was reached. The mean of Scrit and LC50 was 34% (2.4 mg L−1) and 11% (0.8 mg L−1), respectively. The Scrit was independent of fish weight and temperature, whereas the LC50 values were positively correlated with both factors (P < 0.05). The higher resistance in small fish could be due to their greater Vf response to hypoxia than in larger animals. Furthermore, the increased metabolism resulting from the effect of temperature was offset by an increased Vf. The Vf remained constant down to a mean value of 67% oxygen saturation, regardless of fish weight and temperature. These findings suggest an optimum oxygen saturation of above 70% for D. puntazzo culture.

The kinetic profile of oxolinic acid in sharpsnout sea bream, Diplodus puntazzo (Cetti 1777)

The pharmacokinetics of oxolinic acid (OA) were investigated after a single intra-vascular injection (20 mg kg−1 fish) in sharpsnout sea bream (90 g), a promising new euryhaline species for Mediterranean fish farming. The distribution half-life (t1/2α) and the elimination half-life (t1/2β) of OA were calculated to be 0.4 and 10 h respectively. The apparent volume of distribution at steady-state (Vd(ss)) and total clearance rate (CLT) of the drug were found to be 2.1 L kg and 0.2 L kg−1 h−1 respectively. The bioavailability (F%) of OA following oral administration (40 mg kg−1 fish) was estimated to be 15%. The results indicate a rapid distribution and elimination of the drug, moderate tissue penetration, but low absorption in sharpsnout sea bream. The kinetic profile of OA found in this species is comparable with that observed in another well-known sparid, gilthead sea bream.

Effect of feeding rate on fatty acid composition of sharpsnout seabream (Diplodus puntazzo)

The effects of different feeding rates on the lipids fatty acid profile of sharpsnout seabream (Diplodus puntazzo) tissues were studied. During a 15-day period, four fish groups were allowed to feed to satiation, at two-thirds and one-third of satiety, and starved, respectively. Reducing food intake progressively increased the n-3:n-6 relationship by increase of n-3 (mainly Highly Unsaturated Fatty Acids) and decrease of n-6 fatty acid percentages. In perivisceral fat, this n-3:n-6 value was already statistically significant lower for the group fed to satiety (1.29 versus 1.71, 1.80 and 1.65 for the two-third-fed, one-third-fed and fasted groups, respectively), whereas in the white muscle (1.69 versus 2.13 and 2.12) and liver (0.83 versus 1.40 and 2.66) the differences were statistically significant only for the one-third-fed and fasted groups. Linoleic acid was the main contributor to the n-6 drop, whereas the n-3 fatty acids preferentially preserved were for the most part essential fatty acids. Fat quality indices (thrombogenic and atherogenic) were not affected by food restriction except for liver, being the former significantly lower in the one-third-fed and fasted groups. Food intake restriction to one-third of satiety levels was enough to trigger the mechanisms that preserve essential fatty acids.

Effects of fishmeal replacement with soybean meal as protein source, and protein replacement with carbohydrates as an alternative energy source on sharpsnout sea bream, Diplodus puntazzo, fatty acid profile

The effect of replacing fishmeal with soybean meal in the diet and also partial dietary protein replacement with carbohydrates, on sharpsnout sea bream (Diplodus puntazzo) total lipid fatty acid profile was studied. A group of sharpsnout sea bream of 200 g were fed a diet containing either 0%, 20%, 40% or 60% of protein from soybean meal. In a second experiment, fish (126 g) were fed diets with reduced protein and increased carbohydrate percentages. Fishmeal replacement with soybean meal increases the fish polyunsaturated fatty acids (PUFA) content, mainly due to linoleic acid, which is present in high quantities in soya. But as a consequence, the inclusion of soybean meal produces a significant decrease of the n-3/n-6 relationship (from 2.21±0.07 to 1.66±0.05). Replacement of protein with carbohydrate hardly modifies the diet fatty acid profile. As the fishmeal content decreases, there is a slight reduction of saturated fatty acids, the diet with lowest protein percentage having the highest monounsaturated fatty acids and lowest PUFA proportions. Fat quality indices are similar to those reported in previous studies, and in the case of fish under soy-containing diets, they are favourables. However, fishmeal replacement causes a loss of n-3 fatty acids that is important to compensate using other sources rich in this type of fatty acids.

Potential drug (oxytetracycline and oxolinic acid) pollution from Mediterranean sparid fish farms

The potential for input of two common antibacterial agents in Mediterranean fish farms, oxytetracycline (OTC) and oxolinic acid (OA), was estimated from measurements of these drugs in the faecal excretions of two important farmed sparids, gilthead sea bream, Sparus aurata and sharpsnout sea bream Diplodus puntazzo. Oxolinic acid was found to be well absorbed by gilthead sea bream (92%) and sharpsnout sea bream (88%) while the absorption of OTC was found to be considerably lower in both species (27 and 40%, respectively). These data were integrated with production records for sparids, drug dosage regimes and treatment frequency information to calculate potential annual drug release to the aquatic environment from Greek fish farms. These calculations suggest potentially significant quantities of unmetabolised OTC can be passed unabsorbed through the body of treated sparids and excreted via the faeces into the local marine environment. The situation with OA was much less pronounced. It was estimated that potentially more than 1900 kg of OTC and more than 50 kg of OA may be released via faecal excretion into the environment by sparid farms per year. Further drug may also be released via uneaten medicated feed, leached drugs and other routes of fish elimination (renal excretion, branchial secretions). Drug pollution of the marine environment in the vicinity of fish farms can have adverse ecological effects, including development of resistant bacterial populations and exposure with potential drug accumulation in aquatic fauna and flora.

Biochemical egg quality determination in the gilthead seabream, Sparus aurata: reproducibility of the method and its application for sharpsnout seabream, Puntazzo puntazzo

The reproducibility of a recently developed method for egg quality determination in gilthead seabream ( Sparus aurata) eggs was investigated with different broodstock fish and eggs from different stages of spawning time. The method uses activities of acid phosphatase, adenylate kinase, glucose-6-phosphatase, and transaldolase, and levels of amino acids, monosaccharides, and sialic acids as markers and multiple regression models to predict the egg quality. The method has general validity in the present study indicated by highly significant correlations obtained between calculated and experimentally obtained % prehatch survival. Moreover, highly significant correlations were found between predicted % prehatch survival and % posthatch survival. These methods were applied to Puntazzo puntazzo. The multiple regression models for egg quality determination in S. aurata were not useful in this species. However, multiple regression models adapted for P. puntazzo could predict the egg quality with a statistically high significance.

Mesocosm: A Reliable Technology for Larval Rearing of Diplodus puntazzo and Diplodus sargus sargus

Species diversification is today considered as a major issue for the sustainable development of the Mediterranean aquaculture. For successful propagation of any species however, larval rearing is considered a bottleneck and therefore the development of appropriate tools is essential. Mesocosm is a semi-intensive technology that facilitates larval rearing of several species integrating principles of both intensive and extensive aquaculture, which solves biological problems and many of their technical, human and economical consequences. The extensive (and now even the semi-extensive) strategy is used in the most critical segments of the rearing process during the early developmental stages, when larvae are still extremely weak, sensitive to intensive environment, easily stressed and difficult to feed. The intensive strategy is used as soon as larvae are considered mature enough to be reared easily using classical methods. The technology was used for the rearing of two species, with potential for aquaculture, the sharpsnout seabream (Diplodus puntazzo) and the white seabream (Diplodus sargus sargus). Three groups of each species were monitored for a period of 50–70 days post hatching. Survival for both species was about 54% at the end of the trials. Sharpsnout seabream larvae reached 19.6 ± 0.9 mm total length and 107.2 ± 31.9 mg body weight 50 days post hatching. White seabream larvae 60 days post hatching reached 32.7 ± 2.7 mm total length and 450 ± 70 mg body weight. In order to verify the economical viability of the technology, the individual production cost for each species was estimated and reached ¢0.027 for white seabream and ¢0.043 for sharpsnout seabream. Results indicate the reliability of the technology for the larval rearing of the two species.

Growth response and body composition of sharpsnout sea bream (Diplodus puntazzo) fed a high energy diet with different protein levels

A study was undertaken to determine the effect of a high energy diet with two different protein levels on growth, feed efficiency and whole body composition of sharpsnout sea bream (Diplodus puntazzo). Two isoenergetic diets (24.1–24.7 MJ Kg-1 dry weight) with two different protein levels (46.7 and 52.5% dry weight) were fed to satiety to duplicate groups of 300 fish (initial body weight 27.7 ± 0.2 g) for 94 days. At the end of the experiment, the fish fed 52.5% protein showed a statistically higher (P < 0.05) daily intake rate (DIR) of feed. Feed conversion rate (FCR) was similar among groups. Whole body composition was similar among treatments while the high energy level of the diets significantly modified lipid and moisture content in comparison with fish at the beginning of the experiment. Protein efficiency ratio (PER) and gross protein efficiency (GPE) of fish fed 46.7% protein diet were statistically higher than those for the other diet. It may be concluded that the diet with a lower protein level has given better protein utilization and a protein sparing effect but tended to result in reduced weight gain and feed intake, when compared with diet containing higher protein levels.

Mixed Function Oxidase Activity and Organochlorine Levels in Farmed Sharpsnout Seabream (Diplodus puntazzo) from Two Intensive Aquaculture Facilities

Mixed function oxidase (MFO) activities and organochlorine levels were investigated in liver of farmed sharpsnout seabream bred in two intensive facilities, a sea farm and a land-based farm. The aim of this study is to investigate how different facility locations and breeding conditions might affect fish metabolic capabilities and accumulation of toxic chemicals in farmed sharpsnout seabream. The differences between breeding two or more fish species in the same cage or tank known as polyculture, and monoculture (1 species) were also investigated. The results showed that both facility location (sea and land) as well as breeding systems (polyculture and monoculture) might be responsible for the differences observed in both MFO enzyme activity and organochlorine levels. Significantly higher activities of two metabolizing enzymes such as 7-ethoxyresorufin-O-deethylase (EROD) and benzo(a)pyrene monooxygenase (B(a)PMO) were in fact recorded in land-based farmed fish than in sea farmed ones, and much higher in those from polyculture than in monoculture (p < 0.05). By contrast, the highest levels of dichlorodiphenyldichloroethilene (pp′DDE) and polychlorinated biphenyls (PCBs as Aroclor 1260) were measured in sea-farmed fish, except for hexachlorobenzene (HCB), which gave higher levels in land-based farmed fishes. No significant differences were observed between monoculture and polyculture in p,p′DDE and PCBs levels except for p,p′DDE which was significantly higher in monoculture than in polyculture (p < 0.05) in fish reared in tanks. Finally significantly higher HCB levels were measured in fish reared in monoculture in tanks (p < 0.05) and in polyculture in cages (p < 0.05). The low TEQ values obtained for PCB congeners at liver level indicated no concern for fish health.

Poor bioavailability of oxytetracycline in sharpsnout sea bream Diplodus puntazzo

The pharmacokinetics of oxytetracycline (OTC) were investigated following single intravascular injection (40 mg/kg) in sharpsnout sea bream (90 g) at 19 °C. The distribution half-life ( t 1/2 α ) and the elimination half-life ( t 1/2 β ) of OTC were calculated to be 1.4 and 35 h, respectively. The apparent volume of distribution of the drug at steady-state ( V d(ss)) was found to be 4 l/kg. The total clearance rate (CL T) of the drug was low (0.08 l/kg h). Repeated attempts to investigate the bioavailability of OTC following oral administration (75 mg/kg; forced-fed or via the feed), revealed undetectable levels of the drug in plasma and muscle samples. Poor tissue absorption is likely due to significant hepatic metabolism of OTC in sharpsnout sea bream, but this requires further investigation. Thus, oral administration of OTC in farmed sharpsnout sea bream should be discouraged in favour of other routes of administration or other antibiotic drugs.