Effects of dietary microalgae on fatty acids and digestive enzymes in copepod Cyclopina kasignete,a potential live food for fish larvae

The copepod Cyclopina kasignete is a potential live food in aquaculture and its fatty acid components and digestive enzymes were investigated. Three dry algal products (mixed algae, Melosira sp. and Nannochloropsis oculata) and two fresh microalgae (Tisochrysis lutea and N. oculata) were fed to the copepod for 30 days. The essential fatty acids (EFA) in copepods were altered by feeding different types of dry algae. The copepod fed dry Melosira sp. or fresh T. lutea contained higher eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (ARA), protease and trypsin than fed on other algae. The copepod contained a similar fatty acid profile and digestive enzymes by feeding either dry or fresh N. oculata. Between fresh algal species, the copepod fed T. lutea contained higher EPA, DHA and ARA than that fed fresh N. oculata. The amounts of EPA and DHA in copepods were more concentrated than those in the dietary algae, suggesting that the copepod has the ability to accumulate some EFA. This study indicates that dietary algae can modify the nutritional composition and in digestive enzymes copepods, which in turn may be able to transfer suitable nutrients and digestive enzymes to fish larvae in aquaculture.     

Growth and fatty acid composition of juvenile Cerastoderma edule (L.) fed live microalgae diets with different fatty acid profiles

The importance of dietary 20:5n‐3 (EPA), 22:6n‐3 (DHA) and 20:4n‐6 (ARA) for growth, survival and fatty acid composition of juvenile cockles (Cerastoderma edule) was investigated. Cockles of 6.24 ± 0.04 mm and 66.14 ± 0.34 mg (live weight) were distributed into three treatments where live microalgae diets were fed constantly below the pseudofaeces production threshold, for three weeks. Diets had distinct fatty acid profiles: high EPA (53% Chaetoceros muelleri + 47% Pyramimonas parkeae), no DHA (47% Brachiomonas submarina + 53% Tetraselmis suecica) and low ARA concentrations (73% P. parkeae + 27% Phaeodactylum tricornutum). Growth was positively affected by high EPA and low ARA diets, whereas no significant growth was observed for the no DHA diet. High mortality of cockles fed no DHA diet raises questions about its suitability for cockles. In balanced diets with EPA and DHA, lower concentrations of ARA do not limit growth. The impact of dietary fatty acids was evident in the fatty acids of neutral and polar lipids of cockles. In polar lipids of all cockles, there was a decrease in EPA, in contrast to an increase in DHA. The combination of EPA and DHA in a live microalgae diet was beneficial for the growth and survival of juvenile cockles.     

Aurantiochytrium sp. meal as DHA source in Nile tilapia diet,part II: Body fatty acid retention and muscle fatty acid profile

Nile tilapia juveniles (8.35 ± 0.80 g) were fed on four levels (0.0%; 0.5%; 1.0%; 2.0%, 4.0%) of Aurantiochytrium sp. meal (ALL‐G‐RICH?), a source of docosahexaenoic acid (DHA). The 1% Aurantiochytrium sp. meal diet was compared to a control diet, which contained the same amount of DHA as cod liver oil (CLO) at 1.7% diet. Groups of 25 fish were stocked in 100 L tanks and fed twice daily until apparent satiation, for 57 days, at 28°C. Increasing dietary Aurantiochytrium sp. meal reduced the body retention of DHA and n‐3 polyunsaturated fatty acids (n‐3 PUFA) but increased the body retention of alpha‐linolenic (α‐LNA), linoleic (LOA) and n‐6 polyunsaturated fatty acids (n‐6 PUFA). Fatty acid profile in tilapia muscle was affected by increasing dietary inclusions of Aurantiochytrium sp. meal, with an increase in DHA, α‐LNA, n‐3 PUFA and n‐3 long chain‐polyunsaturated fatty acids (n‐3 LC‐PUFA) but a decrease in monounsaturated fatty acids (MUFA), n‐6 PUFA and n‐6 long‐chain polyunsaturated fatty acids (n‐6 LC‐PUFA). There was a larger body retention of DHA, α‐LNA, LOA, n‐3 PUFA and n‐6 PUFA fatty acids and a higher percentage of DHA, n‐3 PUFA and n‐3 LC‐PUFA in muscle fatty acid profile in fish fed on CLO diets than in those fed on 1% Aurantiochytrium sp. Therefore, Aurantiochytrium sp. meal is an alternative source of DHA for Nile tilapia diets.     

Effects of dietary fish oil replacement by microalgae raw materials on growth performance,body composition and fatty acid profile of juvenile olive flounder,Paralichthys olivaceus

Replacing dietary fish oil with DHA‐rich microalgae Schizochytrium sp. and EPA‐rich microalgae Nannochloropsis sp. for olive flounder (Paralichthys olivaceus) was examined. Three experimental isonitrogenous and isolipidic diets with lipid source provided by 50% fish oil (F50S50), 50% (M50F25S25) and 100% microalgae raw material (M100) respectively were compared with a soybean oil (S100) diet as control. Triplicate groups of olive flounder juveniles (16.5 ± 0.91 g) were fed the experimental diets, and a group was fed the control diets for 8 weeks in a recirculation system. Results showed feed efficiency and growth performance were not significantly changed when fish oil (FO) was totally substituted by soybean oil (SO) or microalgae raw material (MRM). The whole‐body composition, lipid content of liver and muscle, and lipid composition of plasma were not significantly influenced by the total substitution of FO by MRM. The polyunsaturated fatty acids (PUFA) content of muscle and liver declined in fish fed S100 diet, whereas it was not significantly reduced in fish fed M50F25S25 and M100 diets. The total substitution of FO by MRM not only maintained the levels of arachidonic acid, EPA or DHA but also increased n‐3/n‐6 ratio. In conclusion, MRM as the sole lipid source is sufficient to obtain good feed efficiency, growth performance and human health value in olive flounder juveniles.     

Rearing the spotted seahorse Hippocampus kuda by feeding live and frozen copepods collected from shrimp ponds

This study evaluated the use of live and frozen copepods collected from shrimp ponds for rearing juveniles of the spotted seahorse Hippocampus kuda. Protein and HUFA contents in frozen copepods were all higher than in Artemia nauplii, the conventional live food for seahorse juveniles. The results of this study showed that copepods can be used as feed for rearing seahorse fry and juvenile. The spotted seahorse showed obvious preference for live copepods and rarely fed on dead copepods on the tank bottom. Furthermore, the combination of frozen copepods and live Artemia nauplii resulted in highest growth and highest survival of the experimental seahorses. Further research on possible effects of DHA:EPA ratio on survival and growth of young H. kuda is recommended.     

Effects of varying dietary docosahexaenoic acid levels on growth,proximate composition and tissue fatty acid profile of juvenile silver pomfrets,Pampus argenteus (Euphrasen, 1788)

This study investigated the effects of varying dietary levels of decosahexaenoic acid (DHA) on growth performance, proximate composition and whole body fatty acid profiles of juvenile silver pomfret, Pampus argenteus. Triplicate groups of fish (30.55 ± 0.08 g) were fed diets containing 5.2%, 9.31% and 13.38% DHA (% of total fatty acids) or 0.85%, 1.52% and 2.18% DHA on dry diet weight for diets 1, 2 and 3 respectively. Survival was not affected by dietary DHA levels. The growth performance and feed utilization parameters of fish fed diets 2 and 3 were significantly (P < 0.05) higher than those fed diet 1, although these parameters in diets 2 and 3 did not differ significantly (P > 0.05). Whole body lipid and fatty acid profiles were influenced by dietary DHA levels. Significantly higher n‐3 fatty acids particularly DHA, DHA:EPA(eicosapentaenoic acid) ratios and n‐3:n‐6 ratios were observed in fish fed diets 2 and 3 compared to those fed diet 1. Better growth performance and higher whole body DHA:EPA (2.31, 2.29) ratios and n‐3:n‐6 ratios (2.17, 2.12) observed in fish fed diets 2 and 3, respectively, suggests that silver pomfret juveniles have a higher requirement for n‐3 fatty acids, notably DHA for optimum growth and survival.     

A Comparison of Growth,Survival, and Fatty Acid Composition of the Lined Seahorse,Hippocampus erectus,Juveniles Fed Enriched Artemia and a Calanoid Copepod,Schmackeria dubia

The purpose of this study was to evaluate the effect of varying dietary levels of highly unsaturated fatty acids (HUFAs) in live prey (Artemia nauplii and a calanoid copepod, Schmackeria dubia) on the growth performance, survival, and fatty acid composition of the lined seahorse, Hippocampus erectus, juveniles. Artemia nauplii were enriched with a commercial product (SS^? 50DE‐microcapsule as HUFA source, 2/3 DHA, 1/3 EPA. Shengsuo Fishery Feed Research Center of Shandong Province, Qingdao, China) at four concentrations of 0.0, 14.0, 28.0, and 56.0. Newly hatched juveniles were cultured for 35 days. The content of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and n‐3 HUFAs in the Artemia nauplii was positively related to the enrichment concentration. At the end of the trials, growth performance of the juveniles was positively related to the enrichment concentration as well. However, the juveniles fed prey enriched with the highest concentration of enrichment (56.0 μL/L) had the significantly lower (P < 0.05) survival rate. The juveniles fed the copepod had the best growth performance and the highest survival rate, suggesting that the copepod, S. dubia, is suitable for feeding the seahorse juveniles. The comparisons between the growth, survival, and fatty acid profiles of the juveniles fed Artemia and copepods indicate that the seahorse juveniles require dietary levels of DHA beyond those achieved by enriching prey with the HUFA enrichment. Surplus EPA resulted from an imbalance between DHA and EPA in the enriched Artemia nauplii probably caused an adverse effect on the seahorse juveniles. This study suggests that DHA and EPA requirement of the lined seahorse juveniles is roughly 32% of total fatty acid, and the optimal DHA/EPA ratio for the species is circa 4:1. To avoid an adverse effect resulting from excessive EPA, maximum proportion of EPA in enriched Artemia nauplii should not exceed 13% of total fatty acid, and a recommended minimum DHA/EPA ratio in the enriched Artemia nauplii is 1.46. Arachidonic acid (20:4n‐6) might not be an essential fatty acid for the seahorse juveniles.     

Differences in fatty acid composition of egg capsules from broodstock spotted babylon, <Emphasis Type="Italic">Babylonia areolata</Emphasis>, fed a local trash fish and formulated diet under hatchery conditions

This study is the first attempt to condition broodstock Babylonia areolata using formulated diets under hatchery conditions. Samples of spotted babylon egg capsules from broodstock fed either a formulated diet or a local trash fish, carangid fish (Seleroides leptolepis) for 120 days were analyzed for proximate composition and fatty acid composition. The formulated diet contained significantly higher levels of arachidonic acid (20:4n − 6; ARA), eicosapentaenoic acid (20:5n − 3; EPA) and docosahexaenoic acid (22:6n − 3; DHA) than those of the local trash fish. The formulated diet also had significantly higher ratios of DHA/EPA and (n − 3)/(n − 6) PUFA than those of local trash fish but not for the ARA/EPA ratio. The compositions of egg capsules produced from broodstock fed formulated diet contained significantly more ARA, EPA and DHA compared to broodstock fed the local trash fish. The ARA/EPA and DHA/EPA ratios in egg capsules were significantly higher in the trash fish—fed group compared to those fed the formulated diet. However, (n − 3)/(n − 6) PUFA ratios in egg capsules produced from broodstock fed the formulated diet did not differ significantly compared to those from broodstock fed the local trash fish. The relatively low DHA/EPA, ARA/EPA and (n − 3)/(n − 6) ratios in the egg capsules produced from the formulated diet—fed broodstock B. areolata suggested that this diet is inferior, when compared to the traditional food of trash fish.     

Effect of diets containing laurel seed oil on growth and fatty acid composition of rainbow trout,Oncorhynchus mykiss

The aim of this study was to determine the effects of replacing fish oil (FO) with laurel seed oil (LSO), as an alternative plant lipid source in diets on the growth and fatty acid composition of rainbow trout (Oncorhynchus mykiss; 111.47 ± 0.2 g mean individual weight). At the end of the feeding trial, survival was 100% in all treatments. No significant differences were seen in growth between the dietary groups (P > 0.05). The protein, lipid and ash contents were not significantly different among the groups (P > 0.05); however, there was a significant difference in protein and ash content between the treatment groups and the initial, and between the 50LSO group and the initial group, respectively (P < 0.05). The viscerosomatic index (VSI) and hepatosomatic index (HSI) values were not affected by increasing LSO percentages in the diets. The n‐6 polyunsaturated fatty acid (PUFA) concentration increased with increasing LSO levels in the diets. In contrast, the n‐3 PUFA levels decreased with increasing LSO levels in the diets. The liver and muscle were used for the analysis of fatty acids. The highest level of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations was recorded in fillet of fish fed the FO diet and the lowest in those fed the 50LSO diet. However, EPA and DHA ratios in the liver of fish fed the 75LSO diet were higher than those in fillet of fish fed the FO and 50LSO diets. No significant differences were seen in fatty acid composition between the dietary groups (P > 0.05). Based on the results of growth performance and fatty acid composition of the experimental fish in this study, it can be concluded that the 75% concentration of laurel seed oil performed best among the diets tested in the experiment.     

Effects of dietary n‐3 PUFA supplements on composition of n‐3 PUFA and expression of fatty acid elongase 5 (AJELOVL5) in sea cucumber,Apostichopus japonicus

This is the first comprehensive study on the effect of dietary polyunsaturated fatty acid (PUFA) levels on the expression of fatty acid elongase 5 (AJELOVL5), PUFA composition, and growth in juvenile sea cucumbers. The specific growth rate (SGR_w) was improved in n‐3 PUFA‐rich diets compared to low n‐3 PUFA diets. AJELOVL5 expression was apparently upregulated in juveniles fed lower PUFA diets relative to higher PUFA diets, with higher expression in the body wall and respiratory tree of juveniles fed diets without ɑ‐linolenic acid (ALA, 18:3n‐3) compared to juveniles fed higher ALA level diets; similar results were also detected in juveniles fed diets with lower eicosapentaenoic acid (EPA, 20:5n‐3), docosahexaenoic acid (DHA, 22:6n‐3), and none of ALA, EPA, or DHA respectively. The concentrations of ALA, EPA, and DHA in tissues were positively related to the content of dietary corresponding PUFA, with higher ALA content in juveniles fed diet ALA_12.71 than in the ALA_7.46 and ALA₀ groups. Similar results were also obtained in sea cucumber fed diets enriched with either EPA or DHA. Interestingly, considerable levels of EPA and DHA were found in the tissues of juveniles fed diets of CK₀ and DHA₀, with no specific input of EPA or DHA, showing that the sea cucumber was capable of biosynthesizing EPA and DHA from their corresponding precursors as ALA and linoleic acid (LA, 18:2n‐6).     

Assessment of the fecundity,population growth and fatty acid composition of Apocyclops royi (Cyclopoida,Copepoda) fed on different microalgal diets

The brackish cyclopoid copepod Apocyclops royi is used in Taiwanese aquaculture industry as a prey for fish larvae. This study investigated the effects of seven microalgal diets, namely single‐species diets of Isochrysis galbana (ISO), Nannochloropsis oculata (NAN), and Tetraselmis chui (TET), two‐species diets (ISO+NAN, ISO+TET and TET+NAN), and a three‐species diet (ISO+NAN+TET), on the population growth, female fecundity and fatty acid composition of A. royi. For reproductive traits, the combination ISO+NAN was found to be the most supportive diet for both population growth and female fecundity. For nutritional value, copepods fed ISO and ISO+NAN were detected to have the highest content of docosahexaenoic acid (DHA) (18.99% and 10.73% total fatty acid, respectively) and, more importantly, a high DHA/EPA ratio (6.09 and 4.09, respectively). Additionally, a comparison of fatty acid composition between copepods and microalgae gives a tentative indication that A. royi may have the ability to synthesize long‐chain polyunsaturated fatty acids (PUFA) from short‐chain PUFA. Our findings illustrate that ISO+NAN is the most suitable microalgal diet for mass culturing A. royi because it increases productivity and enhances the nutritional value of the copepods for use as fish larvae prey.     

Effects of dietary DHA/EPA ratios on growth performance,survival and fatty acid composition of juvenile swimming crab (Portunus trituberculatus)

This study was conducted to investigate the effects of dietary docosahexaenoic to eicosapentaenoic acid (DHA/EPA) ratios on growth performance, survival and fatty acid composition of juvenile swimming crab (Portunus trituberculatus). Four isonitrogenous and isoenergetic experimental diets were formulated to contain different DHA/EPA ratios (0.70, 0.84, 1.06 and 1.25). There were three replicates (15 crabs per replicate) for each diet treatment. The crabs were fed (about 6–8% body weight) twice daily for 8 weeks. A good growth performance and feed utilization were observed in swimming crabs fed the diets with DHA/EPA ratios of 0.70 and 0.84. Crabs fed diet with 0.70 DHA/EPA ratio showed a significantly higher weight gain (WG) compared with the crabs fed the diet with DHA/EPA ratio of 1.25 (P < 0.05). The result of this study showed that the survival increased with decreasing the ratio of DHA/EPA. The DHA/EPA ratios in polar lipid from tissues were influenced by the dietary DHA/EPA ratios. Results of this study indicated that the growth performance and survival of juvenile swimming crab are correlated to the DHA/EPA ratio in the diets, and the best growth performance and survival were achieved with the ratios of 0.70–0.84.     

Fatty acid composition of 12 microalgae for possible use in aquaculture feed

Twelve algal strains representing the classes Cyanophyceae, Prymnesiophyceae, Bacillariophyceae, Rhodophyceae, Cryptophyceae, Chlorophyceae, Xantophyceae and Eustigmatophyceae were selected mainly from the culture collection of the Norwegian Institute for Water Research (NIVA). The algae were grown as continuous cultures in a 1.8 l. reactor, internally illuminated with an 11 W fluorescent tube. The retention time was adjusted in the range 2–4 days to fit the growth rate of the algae. The growth responses and fatty acid composition were analysed. The maximum production rate was obtained with Pseudokirchneriella subcapitata (0.63 g 1⁻¹ day⁻¹) and the lowest with Porphyridium cruentum 0.13 g 1⁻¹ day⁻¹. Arachidonic acid (AA) and eicosapentaenoic acid (EPA) were the dominating polyunsaturated fatty acids (PUFAs) in P. cruentum, while only EPA accumulated in Phaeodactylum tricornutum. Docosahexaenoic acid (DHA) was the major PUFA in Isochrysis galbana, while Pavlova sp. had both EPA and DHA. This is the first report on the fatty acid profiles of Nannochloropsis oceanica, Chroococcus sp., Synechococcus sp. and Tribonema sp.     

The effect of docosahexaenoic and eicosapentaenoic acids in live food on the development of abnormal morphology in hatchery-reared brown sole Pseudopleuronectes herzensteini

We examined the effect of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on the rates of abnormal morphology in juvenile brown sole Pseudopleuronectes herzensteini. Larvae during the D–E stages (15–24 days post hatching) were fed live food containing various amounts of DHA and/or EPA prepared using emulsified oils (DHA ethyl ester, EPA ethyl ester, and corn oil). Larvae during the F–I stages were fed Artemia enriched with a commercial diet supplement. We found that DHA and EPA promoted larval development and improved the incidence of morphological abnormalities in brown sole juveniles to a similar extent. However, DHA was more effective than EPA in preventing the appearance of morphological abnormalities in brown sole. The incidence of normal morphology was clearly improved by an increase of the DHA content in brown sole larvae at 25 days post-hatching. These results suggest that it is important to promote larval development and feed larvae with live food containing high levels of DHA during the D–E stages to prevent morphological abnormalities in brown sole juveniles.     

Effects of dietary docosahexaenoic acid on growth performance,fatty acid profile and lipogenesis of blunt snout bream (Megalobrama amblycephala)

Six diets were designed to investigate the effects of dietary docosahexaenoic acid (22:6n‐3; DHA) levels (0.5, 1.3, 2.3, 4.2, 8.1 and 15.9 g/kg diets) on growth performance, fatty acid profile and expression of some lipogenesis‐related genes of blunt snout bream (Megalobrama amblycephala). Fish (average weight: 26.40 ± 0.11 g) were randomly fed one of six diets for 8 weeks. Results indicated that the final body weight (FBW) and specific growth rate (SGR) of fish fed 1.3 g/kg DHA were significantly higher than other groups except for the 2.3 g/kg DHA (p < .05). Compared with other groups, the number of lipid droplet clusters of the liver stained with oil red O in the 2.3 g/kg DHA group was the highest, which was consistent with the lipid contents of whole body and liver. The DHA proportion in liver and muscle significantly increased with the increasing dietary DHA levels (p < .05), which reflected fatty acid profiles of diets. The highest mRNA expressions of acetyl‐CoA carboxylase α (ACCα), fatty acid synthase (FAS) and sterol regulatory element‐binding protein‐1 (SREBP‐1) occurred in the 1.3 g/kg DHA group, followed by 2.3 g/kg DHA. In summary, the supplementation of 1.3–2.3 g/kg DHA could improve growth performance and lipogenesis, and the dietary DHA could improve DHA and PUFA proportion in liver and muscle.     

Successful rearing of whiteleg shrimp Litopenaeus vannamei larvae fed a desiccation‐tolerant nematode to replace Artemia

The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non‐enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso^®, until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA‐enriched or PUFAs‐enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA‐enriched nematodes (5.1 ± 0.5 mm; 33.1%–44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6.     

Replacement of fish oil with a DHA‐rich Schizochytrium meal on growth performance,activities of digestive enzyme and fatty acid profile of Pacific white shrimp (Litopenaeus vannamei) larvae

This trial was conducted to evaluate the effects of replacing dietary fish oil with Schizochytrium meal for Pacific white shrimp (Litopenaeus vannamei) larvae (initial body weight 4.21 ± 0.10 mg). Six test microdiets were formulated using Schizochytrium meal to replace 0 g/kg, 250 g/kg, 500 g/kg, 750 g/kg, 1000 g/kg or 1500 g/kg fish oil DHA. No significant differences were observed in survival, growth, final body length and activities of digestive enzyme among shrimp fed different diets (p > .05). No significant differences were observed in C20:5n‐3 (EPA) in muscle samples (p > .05). C18:3n‐3 and C20:4n‐6 in muscle increased as Schizochytrium meal replacement level increased (p < .05). No significant differences were observed in C22:6n‐3 (DHA) and n‐3 fatty acids among shrimp fed diets that algae meal replaced 0 g/kg ‐ 1000 g/kg of fish oil. Shrimp fed diet R150 had higher DHA content than other groups and had higher n‐3 fatty acids than that of shrimp fed diets R50, R75 and R100 (p < .05). C18:2n‐6, PUFA and n‐6 fatty acids in muscle increased, while n‐3/n‐6 ratio decreased with increasing algae meal replacement level from 0 g/kg to 1000 g/kg (p < .05). In conclusion, Schizochytrium meal could replace 1500 g/kg fish oil DHA in the microdiets without negatively affecting shrimp larvae survival, growth and activities of digestive enzyme.     

Beef tallow is suitable as a primary lipid source in juvenile Florida pompano feeds

It is assumed that Florida pompano have dietary EPA (20:5n‐3) and DHA (22:6n‐3) requirements. However, it is unclear whether both are equally important in meeting demand for n‐3 long‐chain polyunsaturated fatty acids (LC‐PUFAs) or whether the requirement(s) can be influenced by other fatty acids. Accordingly, we assessed production performance and tissue composition of juvenile Florida pompano (41.0 ± 0.5 g) fed diets containing fish oil; beef tallow; or beef tallow partially or fully supplemented with EPA, DHA or both. After 8 weeks, no signs of fatty acid deficiency were observed. Although fish performance did not vary significantly among the dietary treatments, fish fed the DHA‐supplemented feeds exhibited numerically superior growth than those fed the other diets. Fillets of fish fed the beef tallow‐based diets contained reduced levels of n‐3 fatty acids and LC‐PUFAs and elevated levels of MUFAs and n‐6 fatty acids, although dietary supplementation with EPA and/or DHA attenuated these effects somewhat. Our results suggest that beef tallow is suitable as a primary lipid source in Florida pompano feeds and n‐3 LC‐PUFA requirements may be met by as little as 4 g/kg EPA and 4 g/kg DHA. However, there may be value in supplementing tallow‐based diets with DHA to enhance tissue levels and possibly growth.     

Influence of microalga lipid composition on the sexual maturation of Mytilus galloprovincialis: a hatchery study

The effect of microalga lipid composition on the reproduction of the mussel Mytilus galloprovincialis has been assessed to determine the best feeding strategy for producing large quantities of mussel seed. Three diets based on two microalgae Isochrysis galbana (clon T‐iso) and Chaetoceros gracilis were tested. Besides, hatchery groups were compared with mussels from natural populations. Lipid content and fatty acid profile of digestive gland and mantle of both sexes, eggs and microalgae were analysed and related to sexual maturation. Hatchery groups, specifically the one fed on T‐iso, showed better results in reproduction success, and these differences were reflected on tissue and egg lipid composition. Microalga fatty acid profile influenced tissues and sexes, and higher levels of 18:1n‐9, 22:6n‐3 (DHA) and 18:2n‐6 were detected in groups fed on T‐iso while higher level of 20:5n‐3 (EPA) and 16:1n‐7 in groups fed on C. gracilis. Evidence of synthesis capacity of EPA from 18:4n‐3 and DHA from EPA is detected comparing their levels and the mobilization between tissues. Egg fatty acid profile was influenced by the female diet, and differences among groups were detected and confirmed by PCAs.