The pseudo-green water technique for intensive rearing of sea bream (Sparus aurata) larvae

The pseudo green water technology for sea bream(Sparus aurata) larval rearing was evaluated by analyzingresults of a 2-year study, performed in a pilot scale system. Thetechnology is characterized by the daily addition of phytoplankton in therearing tanks during the first month of rearing. Effects of egg origin,spawningseason and initial larval density on the larval rearing were investigated. Fishreared in pseudo green water systems for 60 days, presented highbiological performance in terms of survival (56 ± 16%), meanweight (62 ± 12 mg), total length (20 ± 1mm), conformity with wild standard (88 ± 9%), andfunctional swim bladder (93 ± 4%). The results present homogenitybetween the categories (origin of eggs, time of spawning, initial egg density)studied, proving the stability of the technology.     

Disinfection of Sparus aurata eggs with glutaraldehyde

This study was conducted to determine suitable conditions fordisinfecting eggs of gilthead sea bream (Sparus aurata)with glutaraldehyde. Effects of the developmental stage (4–8 cells,morula, blastopore closure or heart beating), of the concentration (C = 200,300or 400 ppm) and of the duration of the glutaraldehyde treatment (T= 2 to 10 min) were investigated. Before the blastopore closurestage, egg manipulation and treatment induced mortality. After this stage, thetoxicity of the glutaraldehyde treatment was negligible if the value of theproduct C × T was less than 1000. Above this value, the percentage ofhatching and of normal larvae decreased and the percentage of imprisoned larvaeincreased. Toxic effects of glutaraldehyde varied according to the egg qualityat the time of the treatment. It was concluded that 200 ppmglutaraldehyde for 4 min, at the blastopore closure stage or attheheart beating stage, were acceptable conditions for disinfecting gilthead seabream eggs at 18 °C.     

Pharmacokinetics of ivermectin in sea bream, Sparus aurata using a direct competitive ELISA

The pharmacokinetics of ivermectin in the serum of cultured sea bream, Sparus aurata, after a single intraperitoneal injection of 100 μg kg⁻¹ body weight was studied by the use of direct competitive ELISA. Pharmacokinetic analysis of the serum concentrations versus time points obtained was performed using non-comparmental analysis and a compartmental pharmacokinetic model approach. In the latter case a two-compartment open model with a lag time gave the best fitting. The maximum peak serum concentration was 308.4 ng ml⁻¹ at 2 h post treatment. The AUC of ivermectin was 10700 ng h ml⁻¹ and the elimination half-life 15.37 h, indicating a rapid uptake, high bioavailability and fast elimination of the drug by sea bream. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Effect of an experimental microparticulate diet on the growth, survival and fatty acid profile of gilthead seabream (Sparus aurata L.) larvae

In recent years, a great deal of interest has emerged in the development of microdiets as an economic alternative to live food, in the larval culture of marine fish species. The ability to grow Sparus aurata larvae on a prototype microparticulate diet was examined. To achieve this objective, four feeding regimes differing in the time when the microdiet was introduced (3, 7 or 12 days) and one based exclusively on an inert diet were tested, during the first 22 days of larval life. Significant differences in larval growth were found between the experimental feeding regimes and their corresponding controls (enriched rotifers during the whole experimental period); the larvae in the co-feeding regimes and with an exclusive microparticulate diet were always significantly smaller than larvae fed on rotifers alone. However, the difference was minimised by introducing the inert diet at a later date. A lower survival was found in larvae with a co-feeding regime, in comparison with the control treatments and the survival was significantly lower in larvae fed exclusively on a microparticulate diet. The fatty acid analysis revealed that the experimental microencapsulated diet and the rotifers enriched with Protein Selco® presented relatively similar fatty acid content. In spite of the slightly higher (n?3)/(n?6) and Docosahexaenoic acid (DHA)/Eicosapentaenoic acid (EPA) ratios and somewhat lower highly unsaturated fatty acid (HUFA) content found in the inert diet, the fatty acid composition of the diets cannot explain the differences found in larval performance. The results revealed that the complete replacement of live prey with the tested microparticulate diet is still not possible in S. aurata larval rearing. Nevertheless, better growth and survival results and a substantial reduction in the daily supply of live food can be achieved with a combination of microdiet and live prey.     

The effect of food competition and relative size of group members on growth of juvenile gilthead sea bream, Sparus aurata

The effects of food competition and relative size of group members on growth of sea bream, Sparus aurata were tested in groups composed of four fish. Each group consisted of a medium sized test fish (approximately 250 mg) and three fish larger or smaller than the test fish. In the first experiment food competition was addressed directly by contrasting its presence with its absence. Neither food competition nor relative size of school members had a significant effect on growth. However, there was a highly significant interaction between these two main effects. Under conditions of food competition the medium sized test fish had a three times higher specific growth rate when surrounded by small vs large fish. Under conditions of no food competition when the test fish were separated during feeding a similar but reverse pattern occurred due to differences in food conversion efficiency. In the second experiment, the effects of food quantity and relative size of group members were tested. Both main effects and their interaction were highly significant. Under conditions of low food competition (i.e., surplus food supply) fish grew again better when surrounded by larger fish as compared to their growth rate when surrounded by smaller ones. Size matching via a differential growth rate in a schooling species such as sea bream was suggested to increase the confusion effect by reducing the ability of a predator to focus on an odd sized fish. The implications of direct competition for food for the efficient culture of this species are discussed.     

Effects of dietary polyunsaturated fatty acid/vitamin E (PUFA/tocopherol ratio on antioxidant defence mechanisms of juvenile gilthead sea bream (Sparus aurata L., Osteichthyes, Sparidae)

Lipid peroxidation, specifically polyunsaturated fatty acid (PUFA) oxidation is highly deleterious, resulting in damage to cellular biomembranes, and may be a principal cause of several diseases in fish including jaundice and nutritional muscular dystrophy. Tissue lipid PUFA content and composition are critical factors in lipid peroxidation, as is the level of endogenous antioxidant molecules such as vitamin E. The primary objective of the present study was the characterization of antioxidant systems in a cultured juvenile marine fish, gilthead sea bream (Sparus aurata) with the underlying aim to understand how to avoid oxidation problems that may cause pathologies and disease and so to enhance growth and quality of early ongrowing stages. Juvenile sea bream were fed diets having either high or low levels of fish oil and supplemented or basal levels of vitamin E with PUFA/vitamin E ratios ranging from 117±12 in the diet with low PUFA supplemented with vitamin E to 745±48 in the diet with high PUFA with no additional vitamin E. None of the diets had serious deleterious effects on growth or survival of the fish, but the different dietary regimes were effective in significantly altering the PUFA/vitamin E ratios in the fish livers with values ranging from 5.7±0.4 in fish fed the diet with low PUFA supplemented with vitamin E to 91.1±13.2 in fish fed the diet with high PUFA with no additional vitamin E. This had effects on the peroxidation status of the fish as indicated by the significantly altered levels of in vivo lipid peroxidation products measured in liver, with fish fed the diet rich in PUFA and low in vitamin E showing significantly higher values of thiobarbituric acid reactive substances (TBARS) and isoprostanes. The isoprostane levels generally followed the same pattern as the TBARS levels supporting its value as an indicator of in vivo oxidative stress in fish, as it is in mammals. However, few significant effects on antioxidant enzyme activities were observed suggesting that more severe conditions may be required to affect these activities such as increasing the PUFA/vitamin E ratio or by increasing peroxidative stress through the feeding of oxidized oils.     

Incorporation and metabolism of 14C-labelled polyunsaturated fatty acids in juvenile gilthead sea bream Sparus aurata L. in vivo

The incorporation, and the capacity for desaturation and elongation in vivo, of intraperitoneally-injected, ¹⁴C-labelled n–3 and n–6 C₁₈ and C₂₀ PUFAs were investigated in juvenile gilthead sea bream, Sparus aurata. The results indicate that juvenile gilthead sea bream have only limited ability to convert CH PUFAs to C₂₀ and C₂₂ HUFAs in vivo. The data are consistent with the results from nutritional studies on larvae, postlarvae and fingerlings that have shown that gilthead sea bream require the provision of preformed eicosapentaenoic and docosahexaenoic acids in the diet. The impairment in the desaturase/elongase pathway was quantitatively and qualitatively similar to that found in turbot, Scophthalmus maximus, being at the level of the 5-desaturase. The low activity of 5-desaturase combined with the consistent finding that arachidonic acid is selectively retained in membrane phosphatidylinositol suggests that, in addition to eicosapentaenoic and docosahexaenoic acids, gilthead sea bream may also have a requirement for preformed arachidonic acid in the diet.Abbreviations AA 5,8,11,14-eicosapenaenoic acid (arachidonic acid, 20:4n–6) - CPL diradyl (diacyl + alkenylacyl + alkylacyl) glycerophosphocholine - DHA 4,7,10,13,16,19-docosahexaenoic acid (22:6n–3) - EPA 5,8,11,14,17-eicosapentaenoic acid (20:5n–3) - EPL diradyl (diacyl, alkenylacyl + alkylacyl) glycerophosphoethanolamine - HUFA highly unsaturated fatty acids ( C₂₀ and with 3 double bonds) - LA 9,12-octadecadienoic acid (linoleic acid, 18:2n–6) - LNA 9,12,15-octadecatrienoic acid (-linolenic acid, 18:3n–3) - PI phosphatidylinositol - PS phosphatidylserine - PUFA polyunsaturated fatty acid(s)     

The effect of dietary exogenous digestive enzymes on ingestion,assimilation, growth and survival of gilthead seabream (Sparus aurata,Sparidae, Linnaeus) larvae

The success of microdiets commonly used in the cultivation of marine fish larvae is limited to serving as partial replacements for live food. This limited success is thought to be associated with a reduced digestive ability due to an incompletely developed digestive system. The enhanced growth obtained from live food has been partially attributed to the digestive enzyme activity of the food organism. The present study was designed to test the effect of an exogenous digestive enzyme incorporated. into a microdiet on the growth of Sparus aurata. Larval gilthead seabream, 20–32 days old, were fed ¹⁴C labelled microdiets containing a commercial pancreatic enzyme at different concentrations (0, 0.1 and 0.05g / 100 g dry diet). Rates of ingestion and assimilation were measured and their relationship to dry weight was determined. Our results show that the success of the microdiet as a food for larval gilthead seabream was limited by the larva's low ingestion rate which only approached its maintenance requirement. In addition, the presence of digestive enzyme in the microdiet enhanced its assimilability by 30%. Larval growth over ten days was 0, 100 and 200% on microdiet free of added enzymes, one with added enzymes and a live food regime, respectively. It is our opinion that successful development of microdiets for Sparus aurata must be based on diets improved both in digestibility and attraction to the larvae. Further studies are now underway to determine the nutritional requirements of gilthead seabream larvae using the experimental method developed in the present study. This research was carried out in partial fulfillment of the requirements for the M.Sc. degree.     

Alteration of liver and muscle fatty acid composition in gilthead seabream (Sparus aurata) juveniles held at high stocking density and fed an essential fatty acid deficient diet

The aim of the present study was to determine the combined effect of both stress and EFA deficiency on several biological and biochemical parameters. Fish were fed during 15 weeks two isocaloric and isoproteic diets: a control diet based on fish oil and formulated to meet the n-3 HUFA requirements for this species (1.5% of n-3 HUFA) and a deficient diet containing beef tallow and formulated to be deficient in n-3 HUFA. Each experimental diet was evaluated both at high and low stocking densities (10 and 3.2 kg m^–3 of initial density, respectively).High stocking density produced a chronic stress situation with elevation of plasma cortisol levels. It also caused a reduction in hepatosomatic index and liver lipid contents, increasing the oleic acid/n-3 HUFA ratios in the polar lipids. Fish fed the EFA deficient diet at low stocking density showed common deficiency symptoms. High stocking density in fish fed the EFA deficient diet induced a higher degree of EFA deficiency symptoms leading to mortality, liver steatosis, liver lipid deposition, reduced muscle lipid and reduced n-3 HUFA contents, which particularly affected EPA, but not DHA, suggesting a preferential retention of the latter fatty acid, specially in the phosphoglycerides fraction.     

Effect of in vitro exposure to Vibrio vulnificus on hydroelectrolytic transport and structural changes of sea bream (Sparus aurata L.) intestine

The everted gut sac technique has been used to investigate the effect of Vibrio vulnificus on water and electrolyte (Na⁺, K⁺, Cl⁻, HCO₃ ⁻) transport on the intestine of sea bream (Sparus aurata L.). Both the anterior and the posterior intestine were incubated in a medium containing 10⁸ V. vulnificus cells ml⁻¹ at 25°C for 2 h. The presence of V. vulnificus resulted in a significant reduction (P < 0.05) of water absorption in the anterior intestine, while sodium absorption in the anterior (P < 0.01) and posterior (P < 0.05) intestine was elevated. Chloride absorption was increased, but the changed was not significant, while potassium absorption decreased significantly (P < 0.05), but only in the posterior intestine. Incubation the sea bream intestine with V. vulnificus did not affect carbonate secretion in the anterior segment, whereas high secretion was stimulated in the posterior segment (P < 0.01). Histological evaluations demonstrated damage in the anterior intestine of sea bream that was characterized by the detachment of degenerative enterocytes, alterations in the microvilli, and the presence of a heterogenous cell population, indicating inflammation. Based on our results, we conclude that V. vulnificus caused cell damage to the intestine of sea bream and that the anterior intestine is more susceptible than the posterior part of the intestine. Several hypotheses are suggested to explain our observations, such as the presence of higher numbers of villosities in the anterior intestine than in the posterior one and/or the presence of endogenous bacteria in the posterior intestine which may have a protector role.     

The bioactivity of gonadotropin releasing hormones and its regulation in the gilthead seabream,Sparus aurata: in vivo andin vitro studies

Thein vivo andin vitro potency of native and modified forms of gonadotropin releasing hormone (GnRH) to release gonadotropin (GtH) was studied inSparus aurata and correlated with their relative susceptibility to degradation by cytosolic-bound enzymes of the pituitary, kidney, and liver. Salmon (s) GnRH and luteinizing hormone-releasing hormone (LHRH) are equipotent whereas analogs of these peptides ((D-Arg⁶-Pro⁹NET)-sGnRH, (D-Ala⁶-Pro⁹NET)-LHRH, (D-Trp⁶)-LHRH) are superactive in inducingin vivo GtH release (at 10 μg/kg body weight). In anin vitro superfusion system of pituitary fragments all analogs are equipotent to the native peptides (at 10⁻¹⁰ to 2.5 × 10⁻⁷M). sGnRH and LHRH are rapidly degraded by cytosolic peptidases of the pituitary, liver, and kidney. The preferred site of cleavage is the Tyr⁵-Gly⁶ bond. Substitution of the position 6 glycine by D-amino acids renders the 5–6 bond resistant to degradation and shifts the main site of cleavage to the Pro⁹-Gly¹⁰NH₂ bond. Substitution at position 6 (as above) and at position 10 with Pro⁹NET results in analogs that are resistant to degradation. We propose that enzymatic cleavage terminates GnRH bioactivityin vivo and thus increased resistance to degradation is a major determinant of GnRH analog superactivity.     

黄鳍鲷骨骼肌伴肌动蛋白的纯化及其抗体制备

采用Sephacryl S-400凝胶过滤柱层析和电洗脱等纯化方法,首次从黄鳍鲷骨骼肌中分离纯化到伴肌动蛋白,并制备了特异性多克隆抗体.多克隆抗体经Protein A-Sepharose亲和层析柱纯化得到高纯度免疫球蛋白G(IgG).采用聚丙烯酰胺凝胶电泳(SDS-PAGE)、免疫斑点印迹(Dot-Blot)和免疫印迹(Western-Blot)等方法对纯化的伴肌动蛋白及其多克隆抗体进行分析鉴定,并研究了不同贮藏条件下伴肌动蛋白的变化情况.SDS-PAGE结果显示本研究从黄鳍鲷骨骼肌中分离纯化了高纯度伴肌动蛋白;Dot-Blot检测结果显示兔抗黄鳍鲷伴肌动蛋白多克隆抗体效价为5×104;Western-blot检测表明兔抗黄鳍鲷伴肌动蛋白多克隆抗体能与肌原纤维蛋白中的伴肌动蛋白发生特异性反应,而与其它蛋白不发生免疫交叉反应.     

Heritability of skeleton abnormalities (lordosis, lack of operculum) in gilthead seabream (Sparus aurata) supported by microsatellite family data

Body abnormalities constitute an important problem to fish aquaculture. Pigmentation, scale and skeleton abnormalities have been reported in different cultured fish species. Environmental and genetic factors or their interaction have been suggested to explain their origin. Gilthead seabream (Sparus aurata) is one of the most important European cultured species. Lordosis and lack of operculum are common abnormalities in this species, and can reach frequency of 80% or more of commercial batches. In spite of an important body of data suggesting environmental factors related with their origin, scarce and not conclusive genetic data have been reported to date. In our study, a large number of families originating from the usual production process of a commercial farm were used to estimate the heritabilities of both characters. Two independent experiments were carried out for each abnormality. Nine hundred and ninety four (5.6% lordotics; 157 full-sib families; 6.3 offspring/family) and 808 (7.9% lacking operculum; 83 families; 9.7 offspring/family) individuals were used for lordosis and lacking operculum heritability estimations, respectively. The results obtained adjusting an animal model indicated non significant heritabilities for both characters (0.021 (s.e. 0.019) and 0.032 (s.e. 0.023) for lordosis and lack of operculum, respectively). The corresponding values when a threshold model was used, though higher (0.152 and 0.203, respectively), evidenced large standard errors (0.119 and 0.146, respectively) suggesting h² = 0 as the most confident hypothesis (P = 0.838 and 0.766, respectively). A non-parametric permutation test was also applied to evaluate if more related individuals had a higher phenotypic resemblance. The results obtained suggested only a slight familiar association (P < 0.05) when comparing individuals lacking operculum, but neither between lordotics nor between normal ones. These results suggest that most phenotypic variation observed for lordosis and lack of operculum in gilthead seabream is due to environmental factors.     

A drop in ambient temperature results in a transient reduction of interrenal ACTH responsiveness in the gilthead sea bream (Sparus aurata, L.)

This study investigated the effects of a drop in water temperature (18 °C to 9 °C in 24 h) on the pituitary and interrenal hormones of the gilthead sea bream Sparus aurata. The in vitro sensitivity of the interrenal tissue to ACTH, plasma levels of cortisol, ACTH, -MSH, GH, glucose, lactate and ions were determined. In vitro ACTH, stimulated the release of cortisol from isolated interrenal glands from control gilthead sea bream in a concentration dependent fashion. However, the interrenal cells were less sensitive to ACTH as soon as 24 h following the onset of the temperature drop. At this time, plasma cortisol and ACTH levels were raised, and plasma GH concentrations were decreased, whereas no significant changes were found in plasma -MSH. After 96 h plasma ACTH levels had recovered whereas plasma cortisol levels were still higher than controls after 8 days of the beginning of the experiment. Interrenal sensitivity had recovered after 8 days. The results may help to clarify the relationship between the stress response and the aetiology of the winter syndrome in sea bream.     

Incorporation and metabolism of14C-labelled polyunsaturated fatty acids in wild-caught juveniles of golden grey mullet,Liza aurata,in vivo

The incorporation, and the capacity for desaturation and elongation in vivo, of intraperitoneally-injected,¹⁴C-labelled n-3 and n-6 C₁₈ and C₂₀ polyunsaturated fatty acids (PUFA) were investigated in juvenile golden grey mullet,Liza aurata. The results indicate that juvenile mullet have only limited ability to convert C₁₈ polyunsaturated fatty acids to C₂₀ and C₂₂ highly unsaturated fatty acids (HUFA)in vivo. This suggests that juvenile golden grey mullet require the provision of preformed C_20/22 HUFA, such as eicosapentaenoic and docosahexaenoic acids, in the diet. The impairment in the desaturase/elongase pathway was similar to that found in turbot,Scophthalmus maximus, and gilthead sea bream,Sparus aurata, being primarily at the level of Δ5-desaturase. The data from the largely herbivorous golden grey mullet juveniles are consistent with the hypothesis that marine fish in general, irrespective of dietary habits, have limited capacity for the desaturation and elongation of C₁₈ PUFA. The defect in Δ5-desaturase activity combined with the consistent finding that arachidonic acid is selectively incorporated and retained in membrane phosphatidylinositol suggests that, like turbot and gilthead sea bream, golden grey mullet may also have a requirement for preformed arachidonic acid in the diet.     

Effect of different dietary raw to pre-gelatinized starch ratios on growth performance,feed utilization and body composition of juvenile yellowfin seabream (<Emphasis Type="Italic">Sparus latus</Emphasis>)

The effects of different ratios of dietary raw to pre-gelatinized starch on the growth performance, feed utilization and body composition of juvenile yellowfin seabream (Sparus latus) were evaluated during a 10-week growth trial. Five isonitrogenous, semi-purified diets containing 200 g kg⁻¹ starch comprising different ratios of raw to pre-gelatinized starch [(in g kg⁻¹)100:100 (diet 1), 150:50 (diet 2), 50:150 (diet 3), 200:0 (diet 4), 0:200 (diet 5), raw:pre-gelatinized] were prepared and fed to triplicate groups of juvenile S. latus. Our results showed that fish fed diet 4 (200 g kg⁻¹ raw starch) had the highest weight gain and specific growth rate, followed by those fed diet 2, diet 1, diet 3 and diet 5. Feed efficiency, protein efficiency ratio and protein productive value in the fish on diets 4 and diet 2, respectively, were significantly higher than those on diets 3 and diet 5, respectively. Body and muscle compositions were unaffected by the different dietary raw to pre-gelatinized starch ratios. Values of hepatosomatic index, intraperitoneal fat ratio, viscerosomatic index and condition factor did not vary among experimental treatments. Plasma indices showed variations, but these were not relative to dietary treatments. In conclusion, the partial or total replacement of raw starch by pre-gelatinized starch in diets for yellowfin seabream did not improve its growth performance and feed utilization.     

The in vivo incorporation and metabolism of [1-14C] linolenate (18:3n-3) in liver, brain and eyes of juveniles of rainbow trout Oncorhynchus mykiss L and gilthead sea bream Sparus aurata L.

Accumulation of docosahexaenoic acid (DHA; 22:6n-3) in brain and eyes during development has been demonstrated in fish but it is not clear whether liver or neural tissues themselves are of greater importance in the biosynthesis of DHA from dietary 18:3n-3. In the present study, we investigated the in vivo metabolism of intraperitoneally injected [1-¹⁴C]18:3n-3 in liver, brains and eyes of young juvenile fish. Metabolism was followed over a 48h time-course in order to obtain dynamic information that could aid the elucidation of the roles of the different tissues in the biosynthesis and provision of DHA from dietary 18:3n-3. The study was performed in both a freshwater fish, rainbow trout Oncorhynchus mykiss L and a marine fish, gilthead sea bream Sparus aurata L to determine the effect that low or limiting5-desaturase activity may have in this process. As expected, the results showed that although the sea bream incorporated more 18:3n-3 into its lipids, metabolism of the incorporated fatty acid by de saturation and elongation was generally greater in the trout. In liver, the percentages of radioactivity recovered in tetraene and pentaene products were greater in trout than in sea bream although there was no difference in hexaenes. In contrast, the re covery of radioactivity in DHA was significantly greater in brain in trout compared to sea bream. In both species, the percentage of radioactivity recovered in desaturated/elongated products was much lower in liver than in brains and eyes, but that percentage increased over the 48h time-course. In trout though, the highest percentages of desaturated products in brain and eye were observed after 12 and 24h, respectively. However in sea bream the highest percentages of desaturated products in the neural tissues were observed after 24-48h. Radioactivity was recovered in 24:5n-3 and 24:6n-3, intermediates in the 4-independent ("Sprecher shunt") pathway for the synthesis of DHA, in both species, especially in the brain and eyes. Overall, although the results cannot eliminate a role for liver in the biosynthesis and provision of DHA for developing neural tissues in fish, they suggest that DHA can be synthesised in fish brain and eye in vivo.     

Population ecology parameters and biomass of golden grey mullet (Liza aurata) in Iranian waters of the Caspian Sea

This paper examines the changes in the population ecology parameters and biomass of golden grey mullet (Liza aurata) in Iranian waters of the Caspian Sea from 1991 to 2005. For most years during this 14-year period, we estimated the age structure of the catch, length–weight relationship, von Bertalanffy growth parameters, condition factor, natural and fishing mortality and biomass. Growth parameters were estimated as L_∞ = 62.7 cm, K = 0.15 year⁻¹, t₀ = −0.23 year⁻¹. The instantaneous coefficient of natural mortality was estimated as 0.350 year⁻¹ and the instantaneous coefficient of fishing mortality varied during the 14-year period between 0.111 to 0.539 year⁻¹. Biomass estimates of golden grey mullet, from the biomass-based cohort analysis were increased from 13,527 mt in 1991–1992 to 23,992 mt in 2002–2003. In 2004–2005, it was estimated to be 23,658 mt. We concluded that at the present time, the stock of golden grey mullet is not being over-fished.     

The effect of dietary coconut oil on reproductive traits and egg fatty acid composition in rainbow trout (Oncorhynchus mykiss)

Two hundred and twenty rainbow trouts (IBW: 700 g) were randomly allotted to four tanks, with a male/female ratio of 0.56. Fish were fed for 168 d with four experimental diets containing herring oil, cod liver oil and coconut oil with the following inclusion rates: diet A: 12-1-0% respectively; diet B: 6-1-6%; diet C: 0-1-12%; diet D: 0-0-13%. Irrespective of the dietary treatment, weight gains of broodstocks were high (> 3 g/d) and FCR below 2. No significant difference was observed concerning the total amount of eggs spawn, egg average weight (82.5 mg/egg) and lipid content (5.4 mg/egg). However, the fatty acid profile of eggs was significantly affected by the dietary treatments. The content of unsaturated fatty acids, particularly the n-3 fatty acid series (EPA and DHA) significantly decreased with increasing levels of coconut oil in the diet.