Comparison of heavy metal concentrations in fish samples from three fish farms (Eastern Mediterranean) utilizing antifouling paints

Although aquaculture is considered the fastest growing food production industry, nevertheless there is little information regarding pollutant levels in cultured fish. Samples of cultured sea bass – Dicentrarchus labrax (Linnaeus, 1758), sea bream – Sparus aurata (Linnaeus, 1758), and sharpsnout sea bream – Diplodus puntazzo (Walbaum, 1792) from three fish farms located in the Eastern Mediterranean which utilized antifouling paints on the nets were analyzed for quantitative determination of zinc (Zn), chrome (Cr), and copper (Cu) in the gills, the liver, and the muscle separately for each tissue and fish. The results show that the highest levels of zinc (up to 29.6 mg kg^?1 dry wt) were found in the gills of all samples of sea bream and sharpsnout sea bream while in the samples of sea bass, the highest levels of zinc and chrome were found in the liver (up to 39.3 and 13.8 mg kg^?1 dry wt, respectively). Insofar, as copper is concerned the highest exposure was found in the liver of sharpsnout sea bream (up to 5.49 mg kg^?1 dry wt). The results indicate that the use of antifouling paints in aquaculture practices are a significant source of chemical pollution in cultured fish and poses a risk to the exposed organisms.     

Utilization of yolk reserves during post-embryonic development in three teleostean species: the sea bream Sparus aurata,the sea bass Dicentrarchus labrax,and the pike-perch Stizostedion lucioperca

A comparative study of the use of yolk reserves during post-embryonic development was performed on three teleostean fishes of aquacultural interest: the sea bream Sparus aurata, the sea bass Dicentrarchus labrax, and the pike-perch Stizostedion lucioperca. The first part of the work was devoted to the structural development of the periblast, the vitellus and the oil globule during the endotrophic and endo-exotrophic phases of larval life. Observations using transmission electron microscopy revealed a perivitelline circulation system closely related to the liver, and suggested an important function of the periblast in the utilization of reserves. In the second part of the study, cytochemical reactions revealed the way in which the reserves are resorbed. Glycogen contained in the periblast at hatching was utilized during the endotrophic period. The successive appearance of lipoprotein particles in the periblast endoplasmic reticulum, Golgi apparatus, and perivetelline circulation zone is consistent with the mobilization of yolk and oil globule components. Comparison of fed and fasting individuals revealed that fasting tended to slow down rather than increase the utilization of reserves.     

Interaction of short-term testosterone treatment with osmotic acclimation in the gilthead sea bream <Emphasis Type="Italic">Sparus auratus</Emphasis>

To assess the interaction between testosterone (T) treatment and acclimation to different salinities, seawater-acclimated gilthead sea bream (Sparus auratus) were implanted with slow-release coconut oil implants alone (control) or containing T (5 μg/g body mass). After 5 days, eight fish of control and T-treated groups were sampled. The same day, eight fish of each group were transferred to low salinity water (LSW, 6 ppt, hypoosmotic test), seawater (SW, 38 ppt, control test) and high salinity water (HSW, 55 ppt, hyperosmotic test) and sampled 9 days later. Gill Na⁺, K⁺-ATPase activity increased in HSW-acclimated fish with respect to SW- and LSW-acclimated fish in both control and T-treated groups. Kidney Na⁺, K⁺-ATPase activity was also enhanced in HSW-acclimated fish, but only in T-treated group. From a metabolic point of view, most of the changes observed can be attributed to the action of salinity and T treatment alone, since few interactions between T treatment and osmotic acclimation to different salinities were observed. Those interactions included in treated fish: in the liver, decreased capacity in using glucose in fish acclimated to extreme salinities; in the gills, decreased capacity in using amino acids in HSW; in the kidneys increased capacity in using amino acids in extreme salinities; and in the brain, decreased glycogen and acetoacetate levels of fish in LSW.     

Ontogeny of osmoregulation in the European sea bass Dicentrarchus labrax L.

 Under natural conditions, sea bass eggs hatch in the open sea and young-of-the-year sea bass are found close to estuaries and enter brackish and even freshwater lagoons in the Mediterranean and the eastern Atlantic. The ontogeny of osmoregulation in the European sea bass, Dicentrarchus labrax (Linnaeus, 1758), was studied in different developmental stages, from hatching to large juveniles, exposed to a range of salinities at 17 °C. The experiments were carried out from March to August 1998 in southern France. The type of hyper-hypo-osmotic regulation did not change during development. All stages hyper-regulated at low salinity (under 10–11‰) and hypo-regulated at higher salinities. The acquisition of the full ability to hypo-regulate occurred in four steps. Osmoregulatory capacity was size- and age-dependent and reached its maximum for fish 17–26 mm long, 63–86 days after hatching. The iso-osmotic salinity was 10.2–11.6‰. Our results suggest that early development of osmoregulatory ability, and thus of salinity tolerance in sea bass, may provide an advantageous flexibility for the timing of migration towards low-salinity habitats. Received: 22 May 2000 / Accepted: 18 December 2000     

Studies on the biology of the red sea bream Chrysophrys major III. Metabolic response to starvation in different salinities

Red sea breams were kept at 20°C without food at 3 salinities (full sea water, 950 mOsm kg^-1; 2/3 sea water, 640 mOsm kg^-1; 1/3 sea water, 330 mOsm kg^-1). In fish adapted to all 3 salinities, starvation resulted in marked decline of plasma FFA and -hydroxybutyrate and liver glycogen levels but plasma glucose and lactate concentrations were maintained. These findings suggest that with the onset of starvation, enhanced hepatic glycogenolysis and decreased fat utilization occurred. Fish, adapted to full and 2/3 sea water, could not survive for more than 19 d without food. However, fish adapted to 1/3 sea water could tolerate 27 d of starvation. Enhanced survival during starvation in 1/3 sea water was observed to be associated with maintenance of plasma protein and elevation of hepatic glucose-6-phosphate dehydrogenase activity. It is suggested that sea breams be transferred to an iso-osmotic medium whenever the threat of starvation prevails, but this suggestion has yet to be evaluated in economic terms.Please communicate with Dr. Norman Y. S. Woo     

Effects of sudden changes in salinity on endogenous rhythms of the spotted sea bass Lateolabrax sp.

The endogenous rhythm of oxygen consumption in juvenile spotted sea bass (Lateolabrax sp.) was measured to test the effects of sudden changes in salinity on the metabolic activity. Mean oxygen consumption rates of this euryhaline fish decreased by 13.5 to 16.0% and 25.3 to 36.4% when they were transferred from 31.5 to 15‰ seawater and to fresh water (0‰), respectively. The maximum rate of oxygen consumption was observed between 18:00 and 19:00 hrs local time, 1 to 2 h before sunset, even though they were kept in constant darkness. The peaks of oxygen consumption occurred in 23.2- and 23.3-h intervals, which correspond with a circadian rhythm, as revealed by maximum entropy spectral analysis. A markedly weakened rhythm in oxygen consumption occurred from 8 to 10 d after onset of the experiments. This study indicates that spotted sea bass can withstand sudden drops in salinity from 31.5‰ to fresh water, and yet maintain a regular though somewhat dampened endogenous rhythm of oxygen consumption. Received: 16 June 1997 / Accepted: 3 February 1998     

Locomotor kinematics and behaviour in the escape response of European sea bass, Dicentrarchus labrax L., exposed to hypoxia

To assess the effect of oxygen reduction on the escape response of sea bass, Dicentrarchus labrax, an integrative experimental approach was employed. The effect of hypoxia was tested on locomotor variables, i.e. cumulative distance (D), maximum swimming speed (V _max) and maximum acceleration (A _max). Behavioural variables, such as responsiveness (i.e. the proportion of individuals responding out of the total number of fish tested), response latency (i.e. the time interval between stimulus onset and the first detectable movement leading to the escape of the animal) and directionality (i.e. the proportion of escape responses in which the first detectable movement of the head was oriented away or towards the stimulus at its onset) were also considered. Four levels of oxygen were used: >85% (i.e. normoxia, the control treatment), 50, 20 and 10% of air saturation. Sea bass responsiveness decreased significantly at 10% of air saturation, while hypoxia did not have any effect on the response latency. At the onset of the escape response, the proportion of away/towards responses was random when oxygen was ≤50% of air saturation, suggesting an impairment of the left–right discrimination. Whatever the level of hypoxia, none of the locomotor variables (i.e. D, V _max and A _max) was significantly different from normoxia. Our study suggests that hypoxia may reduce sea bass elusiveness facing a predator by directly affecting its escape behaviour, possibly related to an impairment of the mechano-sensory performance and/or in the Mauthner cells involved in triggering the escape response.     

Bactericidal properties of natural and synthetic sea water as influenced by addition of low amounts of organic matter

The influence of added organic nutrients on the bactericidal capacity of natural and synthetic sea water was investigated, with special reference to levels below the normal concentration of orgnnic matter in natural sea water. Resting cells of Escherichia coli, Staphylococcus aureus and Serratia marinorubra were used as test organisms. The inactivation of test bacteria in synthetic and filter-sterilized natural sea water could be increased by addition of ZoBell's 2216E-broth (containing peptone and yeast extract), peptone or glucose. This effect of the nutrients depended on chemical nature and concentration as well as on specific properties of the test strains. In regard to peptone, less than 10^-4 mg/ml must be added to induce bacterial kill exceeding that observed with unsupplemented controls. With raw sea water, no fundamentally different results were obtained; however, the influence of marine bacteria was clearly discernible. All findings support a previously offered hypothesis of nutrient-dependent antibacterial activity of sea water which is discussed in detail.     

Structure of monogenean populations,ectoparasites of the gilthead sea bream Sparus aurata

In the Western Mediterranean, the gilthead sea bream Sparus aurata Linnaeus, 1758 is parasitized by two gill monogeneans, Furnestinia echeneis (Wagener, 1857) Euzet and Audouin, 1959 (Monopisthocotylea: Diplectanidae) and Sparicotyle chrysophrii (van Beneden and Hesse, 1863) Mamaev, 1984 (Polyopisthocotylea: Microcotylidae). The spatial structure of these parasitic populations were studied on the French coast in the Gulf of Lions in 1984 and 1985. The relations between the two species forming this guild have been demographically analyses. Their distribution profiles are very similar and display some stability with time, although some increasing trends are perceptible in the spring. These two monogeneans are globally frequent, but always present in only moderate intensities in infrapopulations. Recruitment of F. echeneis is independent of that of S. chrysophrii. This mode of contamination limits massive and simultaneous infestations of a single host, and interspecific competition risks are consequently considerably reduced. Our results suggest these parasites can affect the size of a natural gilthead population to only a limited degree.     

Genetic structure of Atlantic and Gulf of Mexico populations of sea bass,menhaden, and sturgeon: Influence of zoogeographic factors and life-history patterns

To assess the influence of zoogeographic factors and life-history parameters (effective population size, generation length, and dispersal) on the evolutionary genetic structure of marine fishes in the southeastern USA, phylogeographic patterns of mitochondrial DNA (mtDNA) were compared between disjunct Atlantic and Gulf of Mexico populations in three coastal marine fishes whose juveniles require an estuarine or freshwater habitat for development. Black sea bass (Centropristis striata), menhaden (Brevoortia tyrannus andB. patronus) and sturgeon (Acipenser oxyrhynchus) samples were collected between 1986 and 1988. All species showed significant haplotype frequency differences between the Atlantic and Gulf, but the magnitude and distribution of mtDNA variation differed greatly among these taxa: sea bass showed little within-region mtDNA polymorphism and a clear phylogenetic distinction between the Atlantic and Gulf; menhaden showed extensive within-region polymorphism and a paraphyletic relationship between Atlantic and Gulf populations; and sturgeon exhibited very low mtDNA diversity both within regions and overall. Evolutionary effective sizes of the female populations (N _f (e)) estimated from the mtDNA data ranged fromN _f (e) = 50 (Gulf of Mexico sturgeon) toN _f (e) = 800 000 (Atlantic menhaden), and showed a strong rank-order agreement with the current-day census sizes of these species. The relationship betweenN _f (e) and the estimated times of divergence (t) among mtDNA lineages (from conventional clock calibrations) predicts the observed phylogenetic distinction between Atlantic and Gulf sea bass, as well as the paraphyletic pattern in menhaden, provided the populations have been separated by the same long-standing zoogeographic barriers thought to have influenced other coastal taxa in the southeastern USA. However, vicariant scenarios alone cannot explain other phylogenetic aspects of the menhaden (and sturgeon) mtDNA data and, for these species, recent gene flow between the Atlantic and Gulf coasts is strongly implicated. These data are relevant to management and conservation issues for these species.Please address all requests for reprints to Dr. J. C. Avise     

Effects of diet on fatty acid composition of body zones in larvae of the sea bass Dicentrarchus labrax: a chemometric study

Larvae of the sea bass Dicentrachus labrax were fed four Artemia sp. diets for 28 d. Three were nauplii enriched with emulsions of polyunsaturated fatty acids, and the fourth nauplii enriched with baker's yeast. At the end of the experimental period, the fatty acids of the bodies, heads and eyes of the larvae were analysed. A multivariate statistical method (discriminant analysis, DA) applied to the data revealed anatomical as well as dietary fatty acid pattern-discrimination. We propose here the use of discriminant analysis as a pattern-recognition method that will help to integrate the fatty acid information obtained in nutritional studies.     

The influence of storage on antibacterial activity of sea water. I. Experiments with sea water stored at 18°C

Three sea-water samples of about 25 l each, stored at 18°C in the dark, were examined for antibacterial activity and bacterial content. Serratia marinorubra mainly was used as test bacterium. During storage for 197 to 454 days, bactericidal capacity varied considerably. In raw sea water, extreme log (N ₃–N ₀) values (N: number of colony-forming test bacteria/ml after 0 and 3 days of any test) were higher than-1 and lower than-4. Antibacterial activity of filtersterilized and autoclaved, stored, sea water likewise varied, but to a lesser degree. The number of colony-forming marine bacteria fluctuated about 3 orders of magnitude. Variations in bacterial content and in bactericidal action of stored sea water were positively correlated during the first months of storage; later, this correlation became negative. From these results it is concluded that variations in nutrient concentration — due to successive periods of growth and autolysis of marine bacteria — were the primary reason for the changes observed in antibacterial activity of stored sea-water samples.     

Maturity classification and group maturity of the red sea bream Pagrus major

The criteria of ovarian maturity during the spawning season and maturity rates according to age are described for the female red sea bream Pagrus major collected from the Chikuzenkai between April and June, 1984. The degree of maturity of the ovary is categorized into four stages based on the maturation stage of the most advanced oocytes in the ovary, rate of atresia and occurrence of post-ovulatory follicles. The ovarian maturity rates in fish aged 2, 3, 4 and 5 years were shown to be 5.8, 46.2, 75.0 and 97.3%, respectively, assuming that yolked ovaries with low levels of atresia (<50% yolked oocytes affected) attain maturity. The fork length at which 50% of the fish attained maturity ranged from 280 to 300 mm.     

The effect of predation on artificial reef juvenile demersal fish species

There is a concern that artificial reefs (AR) may act purely as fishing aggregation devices. Predators attracted to ARs can influence the distribution and abundance of prey fish species. Determining the role of predators in AR is important in advancing the understanding of community interactions. This paper documents the effects of predation on fish assemblages of AR located near a coastal lagoon fish nursery. The Dicentrarchus labrax is a very opportunistic species preying on juveniles (0⁺ and 1⁺ age classes) of several demersal fish species on the ARs. Reef prey and sea bass abundance were negatively correlated. The mean numbers of prey per sea bass stomach increased with the increase of reef fish prey abundance, suggesting that predation has a significant influence, resulting in a decrease in prey abundance. Prey mortality (4–48%) of demersal reef fish associated species depends on bass density. Prey selection was related both with prey abundance and vulnerability. Results showed that D. labrax predation on AR-fish associated species can increase prey natural mortality. However, the role of bass predation on the ecological functioning of exploited ARs is not clear. There may be increases in local fishing yields due either to an increase in predator biomass through aggregation of sea bass attracted to ARs or to greater production. In contrast, predation on juveniles of economically important reef fish preys, especially the most frequent and abundant (Boops boops), can contribute to a decrease in recruitment to the fishery. Our results indicate that inter-specific interactions (predator–prey) are important in terms of conservation and management, as well as for the evaluation of the long-term effects of reef deployment. Thus, it is necessary to consider ecological interactions, such as predation, prior to the development and deployment of artificial habitats as a tool for rehabilitation.     

Predicting aquaculture-derived benthic organic enrichment: Model validation

A sediment trap validation study was conducted near the commercial sea bass and sea bream fish farm in order to assess the predictive capability of a particle tracking deposition model. The validation procedure consisted of two distinct phases. First, the deposition of particulate waste (i.e. fecal pellets and excess feed) was measured near a single net pen containing 19 tons of sea bass. Afterwards, the model quality was determined by statistical comparison of predicted and observed values.Goodness of fit analysis indicates that the model successfully accounts for more than 75% of variance in the observed deposition. At 5% significance level, predictions do not underestimate or overestimate observations and there is no bias. Mean absolute relative error of ±48.9% compares favorably to other published deposition models. Obtained results affirm the reliability of particle tracking techniques in modeling the aquaculture-derived benthic organic enrichment.     

Feeding of laboratory-reared larvae of the sea bream Archosargus rhomboidalis (Sparidae)

Feeding by larvae of the sea bream Archosargus rhomboidalis (Linnaeus) was investigated from late September, 1972 to early May, 1973 using laboratory-reared larvae. Fertilized eggs were collected from plankton tows in Biscayne Bay, and the larvae were reared on zooplankton also collected in plankton nets. Techniques were developed to estimate feeding rate, food selection, gross growth efficiency, and daily ration. Daily estimates of these were obtained through 16 days after hatching at rearing temperatures of 23°, 26°, and 29°C. Feeding rate increased exponentially as the larvae grew, and increased as temperature was raised. At 23°C larvae began feeding on Day 3, at 26° and 29°C larvae began feeding on Day 2. Feeding rates at initiation of feeding and on Day 16 were, respectively: 23°C, 7.16 food organisms per larva per hour (flh) and 53.78 flh; 26°C, 7.90 flh and 168.80 flh; 29°C, 17.62 flh and 142.07 flh. Sea bream larvae selected food organisms by size. At initiation of feeding they selected organisms less than 100 m in width. As larvae grew they selected larger organisms and rejected smaller ones. The major food (more than85% of the organisms ingested) was copepod nauplii, copepodites, and copepod adults. Minor food items were barnacle nauplii, tintinnids, invertebrate eggs, and polychaete larvae. Mean values for gross growth efficiency of sea bream larvae ranged from 30.6% at 23°C to 23.9% at 29°C. Mean values for daily ration, expressed as a percentage of larval weight, ranged from 84% at 23°C to 151% at 29°C and tended to decline as the larvae grew.This paper is a contribution from the Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA     

A laboratory study of behavioral interactions of the Antarctic keystone sea star Odontaster validus with three sympatric predatory sea stars

The circumpolar sea star Odontaster validus is ubiquitous in the nearshore marine benthos of Antarctica. Despite its ecological importance, little is known of its behavioral interactions with other common sympatric sea stars. To examine these interactions we employed time-lapse video analyses conducted in a large laboratory tank (1.8 m diameter circular tank, 1,629 L). In each experimental trial, 34 adult O. validus were placed in a tight circular grouping on one side of the tank, and one adult individual of one of three common sympatric species of predatory sea star (Labidiaster annulatus, Diplasterias brandti, or Perknaster aurorae) was placed on the opposite side of the tank. Digital images of sea star movements were then captured at one min intervals over a 24 h period and aspects of sea star movements subsequently analyzed. Each 24 h treatment was replicated three times, as was a control treatment consisting only of O. validus. O. validus had significantly elevated levels of activity in the presence of P. aurorae when compared with the other two sea stars (potential chemically mediated response), and displayed a distinct “flight response” (change in direction and twofold to sixfold increase of speed) upon tactile contact with this species. Moreover, an “alarm response” was detected when individuals of O. validus that encountered a fleeing conspecific also fled the vicinity. In contrast, our results indicated that O. validus displays virtually no chemical or tactile behavioral responses to the large multi-armed L. annulatus and only weak tactile responses to D. brandti.     

Antibacterial activity of the marine blue-green alga Trichodesmium erythraeum in the gastro-intestinal contents of the sea gull Laurus brunicephalus

The gastro-intestinal contents of the sea gull Laurus brunicephalus Jerdon were found to possess antibacterial activity. This activity could be traced to heavy accumulations of the marine blue-green alga Trichodesmium erythraeum in the gut. During 1969, a bloom of T. erythraeum began in Porto Novo waters about the middle of February, and attained a peak during the second week of March. It has been reported previously by the author that antibacterial properties are exhibited by T. erythraeum maintained in laboratory cultures, as well as in water samples collected from a red tide area. It was also reported (Ramamurthy, 1970) that the gut contents in 2 pelagic fishes, Hilsa kanagurta and Rastrelliger kanagurta, collected during the same red tide bloom period, possessed antibacterial properties. During this period large numbers of these fishes were consumed by sea gulls L. brunicephalus. In view of this finding, experimental procedures were adopted to determine whether extracts of T. erythraeum occurring in the gut of the sea gulls might exhibit antibacterial activity. It was found that T. erythraeum collected from the gut of L. brunicephalus could inhibit both gram positive and gram negative bacteria. Gastro-intestinal extracts from L. brunicephalus collected during the non-bloom period of T. erythraeum showed heavy microbial growth of bacteria and fungi. Evidently, antibacterial or sterile conditions prevail in the gut of these tropical sea gulls in a manner similar to that observed in Polar penguins by Sieburth (1959, 1961).     

Isolation and sequence of cDNA encoding a 3-methylcholanthrene-inducible cytochrome P450 from wild red sea bream,Pagrus major

We have isolated a cDNA clone of mRNA for the cytochrome P450 from a 3-methylcholanthrene (MC)-treated red sea bream,Pagrus major, using a cDNA fragment for rat P4501A2 as a probe. The cloned cDNA is ca. 1.8 kb long and contains an open reading frame of 1545 nucleotides for polypeptides of 515 amino acids. The deduced N-terminal amino acid sequence of the cDNA is very similar to that for purified cytochrome P450 protein from the marine fish scup, which was reported previously (Klotz et al. 1983). A conserved amino acid sequence containing a putative heme-binding cysteine is present in the equivalent position proximate to the C-terminus of the molecules. The deduced amino acid sequence shows more than 50% positional identity with known members of the mammalian aromatic hydrocarbon-inducible P450 family. RNA blot analysis indicates that P450 mRNA (s) is expressed in the liver, kidney, gill and gut of the MC-treatedP. major.     

Genetic structure and allozyme variation of sea bass (Dicentrarchus labrax and D. punctatus) in the Mediterranean Sea

This paper reports data on 28 allozyme loci in wild and artificially reared sea bass (Dicentrarchus labrax) samples, originating from either coastal lagoon or marine sites in the Mediterranean Sea. F _ST analysis (θ estimator) indicated strong genetic structuring among populations; around 34% of the overall genetic variation is due to interpopulation variation. Pairwise θ estimates showed that, on average, the degree of genetic structuring was much higher between marine populations than between samples from lagoons. Six polymorphic loci showed differences in allele frequencies between marine and lagoon samples. Multivariate analyses of individual allozymic profiles and of allele frequencies suggested that different arrays of genotypes prevail in lagoons compared to marine samples, particularly at those loci that, on the basis of previous acclimation experiments, had been implicated in adaptation to freshwater. On the other hand, variation at “neutral” allozyme loci reflects to a greater extent the geographic location of populations. Allozyme differentiation was also studied in a D. labrax population from the Portuguese coast. Average genetic distance between this population and the Mediterranean populations was quite high (Nei's D = 0.236) and calls into question the taxonomic status of the Portuguese population. Finally, genetic relationships between D. labrax and D. punctatus were evaluated. Average Nei's D was 0.648, revealing high genetic differentiation between the two species, even for two sympatric populations of these species in Egypt; thus gene flow was not indicated between species. Received: 24 October 1996 / Accepted: 27 November 1996