Estimation of the period sensitive for the development of abnormal morphology in brown sole <Emphasis Type="Italic">Pseudopleuronectes herzensteini</Emphasis> fed live food enriched with docosahexaenoic acid

The aim of the present study was to clarify the effect of a feeding regimen of live food enriched with docosahexaenoic acid (DHA) on the rates of abnormal morphology in larval brown sole Pseudopleuronectes herzensteini. Live foods were enriched with oil emulsion to produce both high-DHA and low-DHA content. Larvae in group 1 (control) were fed low-DHA-content live foods throughout the experiment. Conversely, larvae in group 2 were fed high-DHA live foods from 15 days post-hatching (dph), when larvae were D stage. Larvae in group 3 were fed high-DHA live foods from 25 dph, when larvae consisted mainly of E stage. The occurrence of normal morphology development in group 2 was significantly higher (P < 0.05) than those of groups 1 and 3, suggesting that normal morphology of brown sole is determined during the critical larval period (D–E stages).     

Three different lipid sources in formulated start-feeds for turbot (Scophthalmus maximus, L.) larvae – effect on growth and mitochondrial alteration in enterocytes

Turbot, Scophthalmus maximus, larvae were start‐fed with formulated feeds containing soya phospholipids (SP), marine phospholipids (MP) or triacylglycerol (TAG). The levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were the same in the MP and TAG feeds. The control group was given rotifers (R). The larvae were offered feed from day 4 post‐hatch. Larvae fed formulated feed with added MP showed good initial growth and there were no significant differences in weight on day 6 between this group and the group given rotifers. Using feed with added TAG enriched with EPA and DHA gave no growth at all. Using SP as the lipid source in the feed resulted in reduced initial growth. Electron microscopical examination of enterocytes was performed on larval intestines on day 6. Larvae fed MP, TAG or rotifers had normal looking enterocytes with numerous normal looking mitochondria. In the enterocytes of larvae fed SP the mitochondria appeared swollen with a translucent matrix and fragmented cristae. Thus, SP or TAG appear not to be suitable as the sole source of lipids and/or phospholipids in start‐feed for turbot larvae and the effects of MP are not solely caused by high levels of EPA and DHA.     

Effects of dietary eicosapentaenoic acid on growth, survival, pigmentation and fatty acid composition in Senegal sole (Solea senegalensis) larvae during the Artemia feeding period

We examined the effect of dietary eicosapentaenoic acid (EPA, 20:5n‐3) on growth, survival, pigmentation and fatty acid composition of Senegal sole larvae. From 3 to 40 days post‐hatch (dph), larvae were fed live food that had been enriched using one of four experimental emulsions containing graduated concentrations of EPA and constant docosahexaenoic acid (DHA, 22:6n‐3) and arachidonic acid (ARA, 20:4n‐6). Final proportions of EPA in the enriched Artemia nauplii were described as ‘nil’ (EPA‐N, 0.5% total fatty acids, TFA), ‘low’ (EPA‐L, 10.7% TFA), ‘medium’ (EPA‐M, 20.3% TFA) or ‘high’ (EPA‐H, 29.5% TFA). Significant differences among dietary treatments in larval length were observed at 25, 30 and 40 dph, and in dry weight at 30 and 40 dph, although no significant correlation could be found between dietary EPA content and growth. Eye migration at 17 and 25 dph was affected by dietary levels of EPA. Significantly lower survival was observed in fish fed EPA‐H diet. Lower percentage of fish fed EPA‐N (82.7%) and EPA‐L (82.9%) diets were normally pigmented compared with the fish fed EPA‐M (98.1%) and EPA‐H (99.4%) enriched nauplii. Tissue fatty acid concentrations reflected the corresponding dietary composition. ARA and DHA levels in all the tissues examined were inversely related to dietary EPA. This work concluded that Senegal sole larvae have a very low EPA requirement during the live feeding period.     

Lipid enrichment for Senegalese sole (Solea senegalensis) larvae: effect on larval growth, survival and fatty acid profile

Results from three larval Senegalese sole (Solea senegalensis) feeding trials using non-enriched Artemia and Artemia enriched with Super HUFA®, Arasco®, sunflower oil and microalgae are presented and the effects on larval survival, growth and fatty acid (FA) composition are reported. The FA profile of Senegalese sole eggs was analysed to gather information about the nutritional requirements of the early larval stages and a quite high DHA/EPA ratio (4.3) was found. However, there was no evidence of a high dietary demand for DHA or EPA, given that no relationship was found between dietary HUFA concentration and larval growth and survival. When larvae were fed non-enriched Artemia a significantly better growth and comparable survival were obtained than with Artemia enriched with Super HUFA® (containing the highest HUFA level and DHA/EPA ratio). The FA profiles of the larvae generally reflected those of their diets. DHA was an exception, as it was present in high proportions, even in larvae fed DHA-deficient prey. Total FAME concentration decreased during larval development, with SFA, MUFA and PUFA being equally consumed; HUFA appeared to be less used, with its relative concentration being either kept constant (particularly EPA and ARA) or increased (DHA). A specific requirement for ARA in the first larval stages could not be confirmed but it was always present in considerable amounts, even in larvae fed an ARA poor diet.     

Influence of highly unsaturated fatty acids in live food on larviculture of mud crab Scylla paramamosain (Estampador 1949)

Two experiments were carried out to investigate the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels in rotifers (Brachionus plicatilis) and Artemia on the survival, development and metamorphosis of mud crab Scylla paramamosain larvae. Five different lipid emulsions, varying in the level of total n‐3 and n‐6 highly unsaturated fatty acids (HUFA), DHA, EPA and ARA were used to manipulate the fatty acid profile of the live food. Fatty acid profiles of the live food and crab larvae at zoea one, three and five stages were analysed to study the HUFA uptake by the larvae. The fatty acid content of the live food affected the fatty acid profiles of the crab larvae. In both experiments, the survival rate in the zoeal stages was not statistically different among treatments. However, larval development rate and metamorphosis success were affected by the dietary treatments. In this respect, the DHA/EPA ratio in the live food seems to be a key factor. Enrichment emulsions with a very high (50%) total HUFA content but a low DHA/EPA ratio (0.6), or zero total HUFA content caused developmental retardation and/or metamorphosis failure. An emulsion with a moderate total HUFA (30%) and a high DHA/EPA ratio (4) was the best in terms of larval development during the zoeal stages and resulted in improved metamorphosis. Dietary ARA seemed to improve first metamorphosis, but its exact role needs further clarification. For the larval rearing of S. paramamosain, an enrichment medium containing about 30% total n‐3 HUFA with a minimum DHA/EPA ratio of 1 is recommended. Further investigation is needed on the total HUFA and optimum DHA/EPA ratio requirements for each crab larval stage.     

Dietary Arachidonic Acid Alters Tissue Fatty Acid Profile, Whole Body Eicosanoid Production and Resistance to Hypersaline Challenge in Larvae of the Temperate Marine Fish, Striped Trumpeter (Latris lineata)

We determined the effect of dietary arachidonic acid (20:4n-6, ARA) on tissue ratios of ARA/eicosapentaenoic acid (20:5n-3, EPA) and subsequent whole body production of the eicosanoids, prostaglandin F_2α (PGF_2α) and E₂ (PGE₂) in the marine larvae of striped trumpeter, Latris lineata. Larvae were also subjected to a hypersaline challenge (55 ppt) with an aim to determine possible relationships between tissue fatty acid profiles, prostanoid production, and their tolerance to osmotic challenge. From 5 to 23 days post-hatch (dph) larvae were fed live food, rotifers (Brachionus plicatilis), that had been enriched with one of five experimental emulsions containing increasing concentrations of ARA and constant EPA and 22:6n-3 (docosahexaenoic acid, DHA). Final ARA concentrations in the rotifers were 1.33, 3.57, 6.21, 8.21 and 11.22 mg g⁻¹ DM. Larval growth and survival was unaffected by dietary ARA. Tissue fatty acid concentrations generally corresponded with dietary fatty acids and final tissue ratios of ARA/EPA ranged from 0.9 to 4.9. At 18 and 23 dph whole body concentrations of PGF_2α and PGE₂ generally increased as more dietary ARA was provided in a dose-response manner, and a significant elevation in both PGF_2α and PGE₂ in larvae fed the highest dietary ARA concentration was recorded at 23 dph compared to larvae receiving the lowest concentration. At 18 dph, the highest cumulative inactivity following a hypersaline challenge occurred in larvae fed 8.21 or 11.22 mg ARA g⁻¹ DM, which was significantly greater than those receiving 3.57 mg ARA g⁻¹ DM. At 23 dph no relationship between inactivity of larvae subjected to a hypersaline challenge to dietary ARA was evident. In summary, dietary ARA altered tissue ARA/EPA ratios, prostanoid production and resistance to a hypersaline challenge in larval striped trumpeter. While increasing dietary ARA generally resulted in elevation of prostanoids as well as increasing the number of inactive larvae following a hypersaline challenge at 18 dph, similar trends between prostanoids and larval inactivity were not evident at 23 dph, suggesting the exact mechanisms and relationships between eicosanoids and larval osmoregulation warrants further investigation. Nevertheless the study provides preliminary data on the effect of dietary ARA on the prostaglandin production in marine fish larvae.     

Effects of salinity and dietary n-3 highly unsaturated fatty acids on the survival,development, and morphogenesis of the larvae of laboratory-reared mud crab <Emphasis Type="Italic">Scylla serrata</Emphasis> (Decapoda,Portunidae)

We investigated the effects of feeding rotifers containing various levels of n-3 highly unsaturated fatty acids (n-3HUFA) to Scylla serrata larvae at different developmental stages on their survival, development, and morphogenesis when they were cultured at six salinity levels. The first-, third-, and fifth (last)-stage zoeae and megalopae were reared to first-stage crabs at salinities of 10, 15, 20, 25, 30, and 35‰, with three different feeding regimes of rotifers containing different levels of n-3HUFA. The larvae successfully developed to the subsequent stages at 20–35‰ salinity. The highest survival rates to first-stage crabs were recorded at 20–25‰ salinity. The morphological features of the megalopa observed in the last-stage zoeae, represented by the ratio of the chela length to carapace length, tended to advance with increasing salinity, indicating higher assimilation efficiency at higher salinities. The megalopal features of the last-stage zoeae were enhanced when the larvae were fed rotifers containing higher amounts of docosahexaenoic acid (DHA). As reported previously, final-stage zoeal larvae with advanced megalopal features often experienced moult death syndrome (MDS). These results show that when larvae are fed rotifers with high DHA under high-salinity conditions, morphogenesis is accelerated, resulting in MDS. Therefore, to evaluate the effects of salinity on larval survival, it is necessary to examine larval morphogenesis in terms of MDS. In conclusion, we recommend that not only survival but also larval morphogenesis should be examined when evaluating the results of rearing experiments with S. serrata larvae.     

Evaluation of Live Feeds for Larval and Postlarval Mahimahi Coryphaena hippurus

Live hatchery feeds were assayed for fatty acids (FA), amino acids (AA), and their ability to support growth and survival of larval and postlarval mahimahi Coryphaena hippurus at two different hatchery stages. Euterpina acuritrons copepods (C), mahimahi yolk-sac larvae (YSL), Artemia parthenogenica brine shrimp nauplii (BSn), A. parthenogenica juveniles (BSj), and Brachionus plicatilis rotifers (R) were assayed, using several enrichment media. There was little difference in AAs among feeds.
Levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were about 10 times higher in YSL than in their feeds. This explains previous findings where first stage larval survival (0–9 days) was not affected by feed HUFA levels. Second stage survival was significantly higher when larvae were fed copepods. Enrichment with 100 ppm SuperSelco greatly improved the survival of larvae that were fed brine shrimp. The even higher omega-3 fatty acids found in copepods appear to be important for survival of larvae under more stressful conditions.
Brine shrimp juveniles enriched with SuperSelco are a good food for postlarval mahimahi. Yolksac larvae of mahimahi are an even better food, promoting faster growth at less cost, for large scale mahimahi aquaculturists. Different batches of yolksac mahimahi larvae varied by a factor of 10 in their concentration of DHA, but always had the highest level of DHA as much as 40% of total fatty acids (FAs). These "high HUFA" batches of YSL also had the highest levels of EPA and total fatty acids. The data suggest that climate and broodstock age may have considerable influence on larval nutrition.     

Effect of EPA/DHA ratios on the growth and survival of Galaxias maculatus (Jenyns, 1842) larvae reared under different salinity regimes

Despite the importance of certain highly unsaturated fatty acids in osmotic regulation, few studies have been addressed to determine the essential fatty acid requirements for a given species cultured under different salinities. As Galaxias maculatus is a diadromic species, the present study aimed to determine the effect of salinity on the optimum dietary EPA/docosahexaenoic (DHA) ratio for survival and growth during the larval stages. Larvae were fed for 20 days with rotifers containing two different EPA/DHA ratios (low: 0.64 and high: 2.18) at three different salinities (0, 10 and 15 g L^?1). The results of this study showed a marked effect of water salinity on larval dietary lipid utilization in G. maculatus larvae. These results suggested that G. maculatus larvae reared at higher salinities may have a higher dietary requirement for DHA, whereas larvae reared at 0‰ showed higher requirements for EPA. The overall results of the present study indicate that even small changes in salinity can determine the optimum dietary EPA/DHA ratio and the quantitative essential fatty requirements of fish. This may have important repercussions and affect the rearing performance of G. maculatus cultured under different salinities.     

Growth and lipid composition of Atlantic cod (Gadus morhua) larvae in response to differently enriched Artemia franciscana

Considerable progress has been achieved in the intensive culture of Atlantic cod (Gadus morhua). However, there is little information concerning optimum live-feed enrichments for cod larvae, since many of the techniques used during the larviculture have been borrowed from other fish species and adapted for the production of Atlantic cod. The present study compared four different protocols for the enrichment of Artemia to be used as live feed for cod larvae. The protocols tested were: (1) AlgaMac 2000, (2) AquaGrow Advantage, (3) Pavlova sp. + AlgaMac 2000, and (4) DC DHA Selco + AlgaMac 2000. Larvae were fed differently enriched Artemia between 37 and 59 days post hatch. At the end of the experiment, larvae from treatment 1 [specific growth rate (SGR) = 10.4 ± 0.4% day⁻¹] grew faster than larvae from treatments 3 (SGR = 6.9 ± 0.2% day⁻¹) and 4 (SGR = 4.9 ± 0.4% day⁻¹, P < 0.0001). However, treatments 3 and 4 resulted in better larval survival at the end of the experimental period, estimated to be 3 on a scale from 1 to 5, whereas the survival estimates for the two other groups were 2. The treatments affected the fatty-acid composition of Artemia and of cod larvae. Larvae from treatment 1 had a higher percentage of AA (20:4ω6, P < 0.0001) and ω6DPA (22:5ω6, P < 0.0001) than the other larvae. Levels of DHA (22:6ω3) were similar in larvae from treatments 1 and 4, and higher than in the other larvae (P < 0.0001). Our results suggest that Artemia containing a DHA/EPA/AA ratio of 7/2/1 result in good larval performance. Joseph A. Brown—Deceased September 2005.     

The Effects of Enriching Live Foods With Highly Unsaturated Fatty Acids on the Growth and Fatty Acid Composition of Larval Red Drum Sciaenops ocellatus

Three experiments were carried out to test the effects of enrichment of live food (rotifers) with varying levels of n-3 highly unsaturated fatty acids (HUFA) on the growth rate and fatty acid composition of red drum larvae. Additionally, the fatty acid compositions of red drum eggs and day-1 larvae were compared. The enrichment techniques were successful in that the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were elevated in the rotifers fed the enrichment diet. Red drum larvae fed the control rotifers produced the highest growth rate of the three experiments. Larvae fed rotifers with no HUFA supplement (NHUFA) had a significantly lower growth rate than the controls for that experiment. The fatty acid compositions of the eggs and day-1 larvae did not vary significantly and contained high levels of 16:0, 16:1 n-7 and DHA (22:6 n-3). Based on these data, the lack of DHA in the diet significantly reduced the growth rates of larval red drum. The 10-day-old red drum larvae had similar fatty acid profiles at the end of the experiments regardless of the diet they were fed, indicating that dietary inputs have little effect on the fatty acid composition of larvae during the first ten days of growth. Red drum larvae appear to have the ability, though limited, to bioconvert EPA to DHA since there was a significant increase in the levels of DHA from day 1 to day 10 in the NHUFA larvae. However, the efficiency of this bioconversion is not sufficient for optimal growth and supplemental DHA at least to the level found in the control rotifers (0.3–0.4mg/100mg tissue) is necessary to maximize growth. The exact role of EPA could not be determined from this study due to the inability to produce an EPA-free rotifer.     

Effect of dietary arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid on survival, growth and pigmentation in larvae of common sole (Solea solea L.)

Evidence confirms that polyunsaturated fatty acids (PUFAs), arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid, DHA are involved in growth as well in pigmentation of marine fish larvae.In the present study we examined the performance of common sole larvae reared on Artemia enriched with 10 formulated emulsions, differing in inclusions of ARA, EPA, and DHA. The specific growth rate of the sole larvae until late metamorphosis, 21 days after hatching (dah) was 20 to 27% d^− 1. Even though the relative tissue essential fatty acid (EFA) concentrations significantly reflected dietary composition, neither standard growth nor larval survival were significantly related to the absolute concentrations of ARA, EPA and DHA or their ratios. This suggests low requirements for essential polyunsaturated fatty acids (PUFAs) in common sole. Malpigmentation was significantly related to increased dietary ARA content. However, pigmentation was not affected by inclusion levels of EPA or DHA when ARA was high. This, and no relation between DHA: EPA or ARA: EPA ratios and pigmentation and only a weak relation to ARA: DHA ratio, advocate for that it is the absolute concentration of ARA in larval tissues, that is responsible for malpigmentation rather than the relative concentration to other PUFAs.Within malpigmentation, the trait “albinism” was characterised by an abnormal incomplete eye migration, but this trait is suggested not to be related to dietary ARA. Furthermore, albinism resulted in a lower growth rate, which suggests that visual aberrations affected prey capture.     

Egg and larval quality,and egg fatty acid composition of Eurasian perch breeders (Perca fluviatilis) fed different dietary DHA/EPA/AA ratios

In Eurasian perch (Perca fluviatilis), the variability in spawning quality is a major limiting factor for successful production, especially when breeders are fed with an artificial diet. The influence of the dietary DHA/EPA/AA ratio on the egg and larval quality and on the fatty acid and lipid class composition of eggs has been investigated in perch broodstock. Two experimental diets (16% lipids) with two different DHA/EPA/AA ratios, D1 (3/2/2) and D2 (23/9/1), were compared with a natural diet consisting of cultured carp juveniles, CC (10/10/1) and with a commercial diet for salmonids, CDS (14/16/1). Percentages of fertilization and hatching were comparable between fish fed D1, D2 and CC, with the highest hatching rate observed for D1 (63.5 ± 3.8%). These diets supported better values than the CDS. Larval survival and TL50 observed after osmotic stress were higher for the D1 group, followed by larvae produced by fish fed D2 and CC. Larvae from fish fed D1, D2 and CC were significantly more robust than larvae from the CDS group. Differences were observed regarding the fatty acid (FA) profile in the eggs, which was related to the dietary FA composition. The results indicate that a ratio of 3/2/2 seemed to be effective for obtaining eggs and larvae of good quality.     

The effect of dietary n-3 HUFA levels and DHA/EPA ratios on growth, survival and osmotic stress tolerance of Chinese mitten crab Eriocheir sinensis larvae

The effect of varying levels of dietary n-3 highly unsaturated fatty acid (HUFA) and docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) ratios on growth, survival and osmotic stress tolerance of Eriocheir sinensis zoea larvae was studied in two separate experiments. In experiment I, larvae were fed rotifers and Artemia enriched with ICES emulsions with 0, 30 and 50% total n-3 HUFA levels but with the same DHA/EPA ratio of 0.6. In experiment II, larvae were fed different combinations of enriched rotifers and Artemia, in which, rotifers were enriched with emulsions containing 30% total n-3 HUFA, but different DHA/EPA ratio of 0.6, 2 and 4; while Artemia were enriched with the same emulsions, but DHA/EPA ratio of 0.6 and 4. In both experiments, un-enriched rotifers cultured on baker's yeast and newly-hatched Artemia nauplii were used as control diets. Larvae were fed rotifers at zoea 1 and zoea 2 stages; upon reaching zoea 3 stage, Artemia was introduced.Experiment I revealed no significant effect of prey enrichment on the survival of megalopa among treatments, but higher total n-3 HUFA levels significantly enhanced larval development (larval stage index, LSI) and resulted in higher individual dry body weight of megalopa. Furthermore higher dietary n-3 HUFA levels also resulted in better tolerance to salinity stress. Experiment II indicated that at the same total n-3 HUFA level, larvae continuously receiving a low dietary DHA/EPA ratio had significantly lower survival at the megalopa stage and inferior individual body weight at the megalopa stage, but no negative effect was observed on larval development (LSI). The ability to endure salinity stress of zoea 3, zoea 5 and megalopa fed diets with higher DHA/EPA ratio was also improved.     

Influence of all-trans retinoic acid on pigmentation and skeletal formation in larval Japanese flounder

ABSTRACT: The effect of all- trans retinoic acid (atRA) on pigmentation and skeletal formation of Japanese flounder Paralichthys olivaceus was investigated. Five groups of flounder larvae were fed live food enriched with 0.5 mL docosahexaenoic acid (DHA) 38G oil containing 10 mg of atRA/10 L of culture medium during different developmental stages; that is, A–B, C–D, E–F, G–H, and I. The control group was fed live food enriched with only DHA 38G oil. Flounder that were fed live food enriched with atRA during the A–B stages showed albinism, and mandible and severe caudal defects (albinism 75.7%, lower jaw defects 75%, caudal defects 100%). Occurrence of these abnormalities in other groups was 0%, 1–4%, and 4.5–10.7%, respectively. Administration of atRA during the A–B stages also caused a high number of vertebrae mainly in the caudal area. Moreover, additional abdominal vertebrae had formed in 25% of fish that were fed live food enriched with atRA in the A–B stages. These results indicate that the effect of atRA is dependent on the developmental stage of flounder larvae and they also suggest that morphological and color abnormalities in flounder were induced by atRA accumulated in live food (rotifers 13 mg/g; Artemia 1.6 mg/g), especially during the A–B stages.     

Lack of essential fatty acids in live feed during larval and post-larval rearing: effect on the performance of juvenile <Emphasis Type="Italic">Solea senegalensis</Emphasis>

Despite the large progress obtained in recent years, Senegalese sole (Solea senegalensis) production of high quality juveniles is still a bottleneck. This paper examines the effect of larval and post-larval lipid nutrition on juvenile performance and quality. Four dietary treatments were tested: A—enriched Artemia spp. (EA); B—non-enriched Artemia spp. (NEA); C—EA during the pelagic larval period and NEA after larval settlement; D—50% EA and 50% NEA. Juvenile fatty acid profile at 60 days after hatching (DAH) clearly reflected the larval and post-larval diet composition. Feeding sole larvae on NEA (poor in lipids and essential fatty acids-EFA) had a negative effect, reducing growth (total length and dry weight) after 30 DAH and decreasing digestive enzyme activity at the end of the rearing period (60 DAH). However, relatively good performance compared to the EFA-richest treatment (A) was obtained when larvae were fed 50% EA and 50% NEA (D) or even EA only during the pelagic larval period followed by NEA after larval settlement (C). Malpigmentation was not affected by the dietary regimes and its incidence was very low. However, skeletal deformities were prevalent, particularly in the caudal complex, independently of diet. The results confirm that Senegalese sole appear to have lower larval EFA requirements than most cultured marine species and potentially even lower requirements during the post-larval stage. The importance of studying the impact of early nutrition on later juvenile stages was clearly highlighted in this study.     

The effect of different HUFA enrichment emulsions on the nutritional value of rotifers (Brachionus plicatilis) fed to larval haddock (Melanogrammus aeglefinus).

A feeding study was conducted in the winter 2001 to determine the effects of feeding rotifers (Brachionus plicatilis) enriched with various levels of essential fatty acids on the growth and survival of haddock larvae (Melanogrammus aeglefinus). Rotifer enrichment treatments were: 1) mixed algae, 2) high DHA (docosahexaenoic acid, 22:6n-3), 3) high DHA and EPA (eicosapentaenoic acid, 20:5n-3), and 4) DHA, EPA, and AA (arachidonic acid, 20:4n-6). Larvae were fed rotifers enriched with the different treatments from days 1 to 16 post-hatch. From day 17 until 25 all treatment groups were fed rotifers reared on mixed algae and then weaned onto the International Council for Exploration of the SEA (ICES) Standard Reference Weaning diet (http://allserv.rug.ac.t/aquaculture/rend/rend.htm) over a five day period. The experiment was terminated on day 41 post-hatch. The enrichment treatments affected the fatty acid composition of the rotifers and correlated with the accumulation of these fatty acids in the haddock larvae. However, no significant differences in larval growth or survival to 40 days post hatch were detected, suggesting that all treatments provided the minimal essential fatty acid requirements for haddock.     

Effects of dietary arachidonic and eicosapentaenoic acids on common dentex (Dentex dentex Linnaeus 1758) larval performance

Oily emulsions containing constant levels of total fatty acids (FAs) and varying eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels were used to enrich rotifers. Common dentex larval survival and growth were compared between groups fed different enriched live prey. Growth, survival rate, and lipid composition of larvae suggest that feeding common dentex in the first 15 days posthatching with 2.5–3% EPA, 6–8% docosahexaenoic acid (DHA), and DHA/EPA ratio of 2.0–2.5 is sufficient to fulfill their EPA requirements. Higher amounts of dietary EPA did not result in any significant improvement in growth or survival. EPA requirement during this period of larval development does not seem to be as critical as other FAs during the first 15 days of common dentex larval development, but it does not exclude its essentiality later in development. In the case of ARA, nutritional requirements are low compared to other marine finfish species, with the upper limit of this essential FA being around 2% of total FAs provided in the live prey composition.     

Changes in lipid content, fatty acid composition and lipid class composition of eggs and developing larvae (0–40 days old) of cultured common dentex (Dentex dentex Linnaeus 1758)

Total lipid content, fatty acid (FA) composition and lipid class composition of common dentex eggs spawned at different times and larvae reared under different culture conditions until 40 days posthatch (dph) were analysed to get a general pattern of lipid composition during larval development. Two groups of larvae were kept under starvation to compare their FA composition with that obtained from normally fed larvae. To compare FA use or accumulation during larval development, results were grouped according to the developmental stage of the larvae instead of age in days posthatch. Saturated and monounsaturated FAs decreased along larval development, while polyunsaturated fatty acid (PUFA) content increased. The ratio of docosahexaenoic acid (DHA)/eicosapentaenoic acid shifted from 4 to 5 in early developmental stages to lower than 1 after metamorphosis. Arachidonic acid levels remained constant along larval development. Larvae kept 6 days under starvation consumed most of their n-3 PUFA while conserving the DHA to values at day 0. The results presented here are useful for the design of nutritional experiments, because there were differences detected in terms of lipid and FA composition between developmental stages with higher differences mainly found in first-feeding larvae and early developmental stages.     

Effects of dietary docosahexaenoic acid (22:6n‐3) and arachidonic acid (20:4n‐6) on the growth,survival, stress resistance and fatty acid composition in black sea bass Centropristis striata (Linnaeus 1758) larvae

The objectives of this study were to determine the effects of the dietary docosahexaenoic acid (DHA) to arachidonic acid (ARA) ratio on the survival, growth, hypersaline stress resistance and tissue composition of black sea bass larvae raised from first feeding to metamorphic stages. Larvae were fed enriched rotifers Brachionus rotundiformis and Artemia nauplii containing two levels of DHA (0% and 10% total fatty acids=TFA) in conjunction with three levels of ARA (0%, 3% and 6% TFA). On d24ph, larvae fed the 10:6 (DHA:ARA) treatment showed significantly (P<0.05) higher survival (62.3%) than larvae fed 0:0 (DHA:ARA) (27.4%). Notochord length and dry weight were also significantly (P<0.05) greater in the 10:6 (DHA:ARA) treatment (8.65 mm, 2.14 mg) than in the 0:0 (DHA:ARA) (7.7 mm, 1.65 mg) treatment. During hypersaline (65 g L⁻¹) challenge, no significant differences (P>0.05) were observed in the median survival time (ST50) between larvae fed 10% DHA (ST50=25.6 min) and larvae fed 0% DHA (ST50=18.2 min). The results suggested that black sea bass larvae fed prey containing 10% DHA with increasing ARA within the range of 0–6% showed improved growth and survival from first feeding through metamorphic stages.