Seasonal variations of lipid fatty acids of boreal freshwater fish species

1. The fatty acid levels of muscle and liver lipids of perch, vendace and rainbow trout (Salmo gairdneri) cultivated in the same area (for comparison) were monitored. 2. The total lipid content in the muscle of perch (Perca fluviatilis) and vendace (Coregonus albula) was less than 50% of that in rainbow trout and a seasonal variation was clear only in vendace. 3. The relative amounts of polyunsaturated fatty acids as well as omega-3 acids were higher in vendace and perch than in cultivated rainbow trouts. Arachidonic acid content was much higher in vendace and perch than in rainbow trout. The content of monoenes was considerably higher in rainbow trout than in free freshwater fish. 4. The seasonal variations in the degree of unsaturation were small in fish muscle. 5. In the muscle of rainbow trout the relative amount of polyunsaturated fatty acids diminished with the increase of total lipids.     

Multi-component analysis of marine lipids in fish gonads with emphasis on phospholipids using high resolution NMR spectroscopy

High resolution NMR has been applied for assessment of lipid classes and acyl stereospecific positions of fatty acids in marine phospholipids and triacylglycerols. 1D and 2D NMR techniques in combination with recording of a number of reference standards have been used to interpret the (1)H and (13)C NMR spectra of fish gonads. (13)C NMR spectra gave information regarding the polyunsaturated fatty acids (PUFAs) in phosphatidylcholine (PC) and phosphatidylethanolamine (PE). The carbonyl resonances showed that n-3 PUFAs primarily were esterified in the sn-2 position of PC and PE. The glycerol resonances showed that the PC/PE ratio was higher in roe than in milt and that roe comprised more triacylglycerols than milt. Thin layer chromatography showed that milt contained 2.4 times more cholesterol than roe, which was also found by integrating the (1)H NMR spectra. Concentration (mol%) of n-3 fatty acids were calculated from the (1)H NMR data and showed 44.8 and 36.3% in roe and milt, respectively.     

Predator odor recognition and antipredatory response in fish: does the prey know the predator diel rhythm?

We studied in a laboratory experiment using stream tanks if two percid prey fish, the perch (Perca fluviatilis) and the ruffe (Gymnocephalus cernuus), can recognize and respond to increased predation risk using odors of two piscivores, the pike (Esox lucius) and the burbot (Lota lota). Burbot is night-active most of the year but pike hunts predominantly visually whenever there is enough light. Perch is a common day-active prey of pike and dark-active ruffe that of burbot. We predicted that besides recognizing the predator odors, the prey species would respond more strongly to odors of the predator which share the same activity pattern. Both perch and ruffe clearly responded to both predator fish odors. They decreased movements and erected the spiny dorsal fins. Fin erection showed clearly the black warning ornamentation in the fin and thus erected fin may function besides as mechanical defense also as warning ornament for an approaching predator. No rapid escape movements were generally observed. Both perch and ruffe responded more strongly to pike odor than to burbot. There were no clear differences in response between day and night. In conclusion, we were able to verify clear predator odor recognition by both prey fish. Both perch and ruffe responded to both predator odors and it seemed that pike forms a stronger threat for both prey species. Despite of diel activity differences both perch and ruffe used the same antipredatory strategies, but the day-active perch seemed to have a more flexible antipredatory behavior by responding more strongly to burbot threat during the night when burbot is active.     

Studies on lesions caused by plerocercoids of Triaenophorus nodulosmin some fish of an alpine lake, the Königssee

Lesions caused by plerocercoids of Triaenophorus nodulosus in the second intermediate hosts were studied in fish of an alpine lake, the Königssee. Four species (Arctic charr, Salvelinus alpinus; minnow, Phoxinus phoxinus; burbot, Lota lota: perch, Percafluviatilis) could be shown to be affected, whereas seven other fish species did not have macroscopical or histological signs of invasion. The capsules of T. nodulosus plerocercoids were usually located in liver tissue. Whereas only living parasites were found in charr and minnow, dead and destroyed plerocercoids could be demonstrated additionally in burbot and perch.
The histological picture is characterized by capsules surrounded by connective tissue and by fresh or older migration routes in charr and minnow. Furthermore, larvae migrating through the biliary ductules were found regularly in charr. In burbot and perch, different stages of destruction of the parasitic larvae took place. The ability to reject the parasite by immunological reactions seems to depend on the species of host. Even if heavy changes in the liver tissue could be demonstrated, no negative influences on condition and growth of affected fish could be established.     

Studies on furan fatty acids of salmon roe phospholipids

Mature salmon roe lipids were found to consist of triacylglycerols (63%), phospholipids (30%), sterols (4.2%), steryl esters (0.7%), and other minor components. In the steryl esters and phospholipids, furan fatty acids were detected instead of the triacylglycerols of the testes lipids in male fish. The representative 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid (F6) amounted to 3.8% and 0.6% of the total fatty acids in each fraction, respectively. However, the absolute amount of the acid in the phospholipid was much more than that contained in the steryl esters. The characteristic distribution of the furan acids found in the phospholipids was common to the steryl esters in the liver. Large amounts of furan acids were contained in phosphatidylcholine (PC) rather than in phosphatidylethanolamine. For positional analysis of furan fatty acids in PC, furan-containing species in the molecule were concentrated fourteenfold by using selective hydrogenation and repeated silica gel column chromatography. A series of furan fatty acids in PC was found to be exclusively linked to the sn-1 position. The amount of the acids in the roe exclusively linked to the sn-1 position. The amount of the acids in the roe phospholipids was comparable with that in the testes triacylglycerols. The physiological roles of furan fatty acids are discussed.     

Utilization of porcine pancreatic phospholipase A2 for the preparation of a marine fish oil enriched in (n - 3) polyunsaturated fatty acids

A simple and rapid method is described for the preparation of a marine oil fraction highly enriched in (n - 3) polyunsaturated fatty acids. Cod roe, containing lipid up to 15% of its dry weight, approximately 70% of which is phospholipid, was the starting material. Incubation of a concentrated aqueous extract of the roe with porcine pancreatic phospholipase A2 (EC 3.1.1.4) was the key step in the procedure. Extraction of the freeze-dried reaction product with diethyl ether containing formic acid produced an oil in a yield of 1.0 g/100 g wet wt of starting roe. The oil contained over 95% as free fatty acids, with 20:5 (n - 3) and 22:6 (n - 3) accounting for up to 24 and 40%, respectively, of the total free fatty acids. The therapeutic use of the oil is mentioned.     

Comparison of fatty acid profiles of spawning and non-spawning Pacific herring, Clupea harengus pallasi

Crude lipid and fatty acid composition from liver, intestine, roe, milt and flesh of spawning and non-spawning Pacific herring (Clupea harengus pallasi) were examined to determine the relative effects of spawning on the nutritional value of herring. Depletion of lipid due to spawning condition was significant (P < 0.01) in all organ tissues and flesh of spawning herring. The lipid content ranged from an average of 1.9 to 3.4% (wet weight basis) in different organ tissues of spawning herring, to 10.5 to 16% in non-spawning fish. The fatty acid profile exhibited many differences in the relative distribution of individual fatty acids among organ tissues and between the two fish groups. Oleic acid (C18:1n-9), a major monounsaturated fatty acid (MUFA) found in all tissue lipids, decreased significantly (P < 0.01) in spawning fish. The two monoenes, C20:1n-9 and C22:1n-11, occurred at high concentrations in the flesh but at only minor proportion in the digestive organs and gonads. Spawning herring also had significantly (P < 0.01) higher polyunsaturated fatty acids (PUFA) content in the organ tissues, particularly in the milt and ovary, with docosahexaenoic acid (C22:6n-3, DHA) having the greatest proportion. Among the n-6 fatty acids, only C18:2n-6 and C20:4n-6 occurred at notable amounts and were present in higher proportions in spawning fish. We concluded that although relatively higher n-3 fatty acid content was found in the organ lipids of spawning herring, they are not an energy-dense prey food source due to the fact that both flesh and gonads contain a very low amount of lipid.     

Ontogenetic niche shifts and resource partitioning in a subarctic piscivore fish guild

The feeding ecology of three piscivorous fish species (perch (Perca fluviatilis), pike (Esox lucius) and burbot (Lota lota)), was studied in the subarctic Pasvik watercourse (69 °N), northern Norway and Russia. All three species primarily occupied the benthic habitats in the watercourse. Perch and burbot exhibited distinct ontogenetic niche shifts in food resource use, perch changing from a dominance of zooplankton to zoobenthos to fish, and burbot from zoobenthos to fish. Fish prey dominated the diet of all the investigated size-classes of pike, but small-sized pike (<20 cm) were not represented in the sample. Fish prey size was positively related to predator size in all three species. Whitefish (Coregonus lavaretus) was the dominant prey of pike and large-sized burbot and perch. Nine-spined sticklebacks (Pungitius pungitius) was also an important prey and appeared to be a dietary stepping-stone enhancing the transition from invertebrate feeding to consumption of large-sized whitefish prey for all three predators. A cluster analysis separated the different size groups of the three predator species into five functional feeding groups, most of them containing two or all three species. Within these feeding groups, and especially among the piscivorous size-classes, there was a strong and significant interspecific overlap in prey selection, and the dietary similarities between the species were in general much larger than the intraspecific similarities between ontogenetic stages. All three piscivorous species are important top predators in the aquatic food web of the watercourse, and their ontogenetic diet shifts and resource partitioning patterns generate a substantial food web complexity in this subarctic ecosystem.     

Gastric evacuation rate of burbot fed single-fish meals at different temperatures

The gastric evacuation rates of burbot Lota lota , fed a single meal of vendace, Coregonus albula , were measured in the laboratory at five temperatures (1·3, 2·6, 4·8, 9·4 and 12·6° C). Gastric evacuation rate increased exponentially with increasing temperatrure, but the results suggest that gastric evacuation rates of burbot at low temperatures are lower than those of other freshwater fish species. Temperature and the ratio of meal weight to burbot weight were the most important factors affecting gastric evacuation rate. There was no significant difference in gastric evacuation rate between three different prey species: vendace, perch Perca fluviatilis , and smelt Osmerus eperlanus .     

Gillnet selectivity and the efficiency of alternative combinations of mesh sizes for some freshwater fish

The selectivity curves of nylon gillnets for burbot and two groups of Arctic charr of different fatness were found by the Gulland-Harding method. They are compared to the selectivity curves of whitefish, brown trout, and perch. Based upon these curves and the relationships between most efficient mesh size and fish length, the pooled relative efficiency of a geometrical and an arithmetical series of mesh sizes was calculated for salmonids, burbot, and perch. This efficiency of the geometrical series is different for the three groups of fish, but equal for each group over the interval between the modal lengths of the smallest and largest mesh sizes. The efficiency of the arithmetical series is also different for the three groups, increases linearly with fish length, and is valid over the interval between the modal lengths of the second smallest and the second largest mesh sizes. Each series has its special advantages, and both are easily adjusted to the fish length interval of interest. They are especially adapted for the catch of salmonids. For these, the variations of condition factor is more important than any characteristics of the species, and its influence upon the most efficient mesh size to fish length relationship and the pooled relative efficiency of the two series of nets is evaluated.     

Comparing fish catches taken with gill nets of different combinations of mesh sizes

Based on net selectivity curves and the pooled relative efficiency of combinations of mesh sizes, models for comparing gill-net catches taken with different combinations of mesh sizes are presented for perch, burbot and, in more detail, for salmonids. The models enable comparison of length frequencies and the numbers of fish within any length range caught with an acceptable net efficiency. A standard for comparing salmonids is proposed.     

The effects of dietary (n-3) fatty acid supplementation on lipid dynamics and composition in rat lymphocytes and liver microsomes

Rats were fed diets devoid of (n-3) fatty acids (olive oil supplementation) or high in (n-3) fatty acids (fish oil supplementation) for a period of 10 days. In spleen lymphocytes and liver microsomes derived from animals fed fish oil diets, relatively high levels of (n-3) eicosapentaenoic (20:5), docosapentaenoic (22:5) and docosahexaenoic acids (22:6) were obtained compared to minimal levels when fed the olive oil diet. When the average lipid motional properties were examined by measuring the fluorescence anisotropy of diphenylhexatriene, no significant different was found between intact liver microsomes from animals fed the two diets. However, when lipid motion was examined in vesicles of phosphatidylcholine, isolated from the microsomes from fish oil fed animals (21.4% (n-3) fatty acids), the fluorescence anisotropy was significantly less than the corresponding phosphatidylcholine from olive oil fed animals (5.6% (n-3) fatty acids), indicating a more disordered or fluid bilayer in the presence of higher levels of (n-3) fatty acids. Phosphatidylethanolamine (n-3) fatty acids were also elevated after fish oil supplementation (41.3% of total fatty acids), compared to the level after olive oil supplementation (21.4%). The major effect of the fish oil supplementation was a replacement of (n-6) arachidonic acid by the (n-3) fatty acids and when this was 'modeled', using liposomes of synthetic lipids, 1-palmitoyl-2-arachidonyl(n-6) or docosahexaenoyl(n-3)-phosphatidylcholine, significant differences in lipid motional properties were found, with the docosahexaenoate conferring a more disordered or fluid lipid environment. Thus it appears that although lipid order/fluidity can be significantly decreased by increases in the highly unsaturated (n-3) fatty acid levels, alterations in membrane domain organization and/or phospholipid molecular species composition effectively compensated for the changes, at least as far as average lipid motional properties in the intact membranes was concerned.     

Lipid and fatty acid composition of muscle and liver from wild and captive mature female broodstocks of white seabream, Diplodus sargus

Total lipids (TL), lipid classes, and their associated fatty acids from muscle and liver of captive and wild mature female broodstocks were investigated in order to estimate the fatty acid requirements of white seabream (Diplodus sargus). The results showed that the percentage of triacylglycerol was higher in liver and muscle of captive fish than in wild fish. The distribution of phospholipid classes in liver and muscle of both fish groups was similar, phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol being the predominant lipid classes. The general pattern of fatty acid distribution in total lipid of liver and muscle from captive and wild fish was similar. However, the relative percentage of specific fatty acids differed in captive and wild fish. The most noteworthy difference was the lower proportion of arachidonic acid (20:4n-6, AA) and the higher proportion of eicosapentaenoic acid (20:5n-3, EPA) in liver and muscle of captive fish with respect to those of wild fish. The proportion of docosahexaenoic acid (22:6n-3, DHA) did not differ between the two fish groups. The differences in EPA and AA proportions between captive and wild fish implied that captive fish presented a higher EPA/AA ratio and a lower DHA/EPA ratio than wild fish. In general terms, in both liver and muscle, the differences in fatty acid composition observed for TL were extended to all lipid classes. The results suggest that the different AA, EPA and DHA proportions in liver and muscle between captive and wild broodstocks are attributed to different levels of these fatty acids in broodstock diets.     

L-fucose-specific lectin from pike perch (Lucioperca lucioperca L.) roe. Purification and studies of carbohydrate specificity

L-fucose-specific lectin was purified from pike perch (Lucioperca lucioperca L.) roe by affinity chromatography on ovariomucine H-sepharose from a human ovary cyst. Three bands were detected after disk-electrophoresis in PAAG in alkaline (pH 8.9) and five bands--in acidic system (pH 4.3). According to electrophoresis data in 15% SDS-PAGE the lectin contains two components with molecular weight 13-14 kDa. Molecular weight of the lectin is 50 kDa according to gel-chromatography on tojopearl HW-55. The immunochemical properties of the lectins from perch (Persa fluviatilis L.) roe and pike perch (Lucioperca lucioperca L.) roe are similar.     

Fatty acid composition of muscle and heart tissue of Nile perch,Lates niloticus,and Nile tilapia,Oreochromis niloticus,from various populations in Lakes Victoria and Kioga,Uganda

The fatty acid composition in the heart tissue and muscle tissue of the Nile perch, Lates niloticus, and Nile tilapia, Oreochromis niloticus populations from Lakes Kioga and Victoria was determined by methanolysis and gas chromatography of the resulting fatty acid methyl esters. The analytical data were treated by multivariate principal component analysis. The most abundant individual fatty acids were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1n9), vaccenic acid (18:1n7), arachidonic acid (20:4n6) and docosahexaenoic acid (22:6n3). Due to high levels of both n6 and n3 fatty acids, the ratios of n3 to n6 were between 1 and 2, typical for freshwater fish species. Two Lake Victoria and one Lake Kioga populations of Nile tilapia and Nile perch were distinguished by the fatty acid profiles in their heart and muscle tissue. The heart tissue showed better separation than muscle tissue, due to dominance of polar phospholipids. It is rationalised that genetics are more important than diet in determining the fatty acid composition of the tissues.     

鱼类脂肪与脂肪酸的转运及调控研究进展

由于鱼油资源短缺, 植物油在水产饲料中广泛使用。然而, 随之而来的鱼体脂肪异常沉积等问题也日益突出, 严重危害养殖鱼类健康。脂肪的沉积是一个复杂的过程, 主要包括脂肪的合成、转运和分解。到目前为止, 在鱼类中已经进行了大量关于植物油替代鱼油影响脂肪沉积的研究。但是, 这些研究主要集中于脂肪的合成和分解, 有关脂肪转运的研究十分缺乏。脂肪转运不仅是影响组织脂肪沉积的重要因素, 而且在机体脂稳态和能量平衡中起着重要作用。因此综述了鱼类脂蛋白的种类和组成, 鱼类对脂肪和脂肪酸的转运, 营养因素对脂肪和脂肪酸转运的影响, 指出了脂类转运研究的重要性和紧迫性, 并且提出了未来需要努力的方向。     

Effect of fish and fish oil-derived omega-3 fatty acids on lipid oxidation

There is evidence that omega-3 (omega3) fatty acids derived from fish and fish oils reduce the risk of cardiovascular disease via mechanisms underlying atherosclerosis, thrombosis and inflammation. Despite these benefits, there has been concern that these fatty acids may increase lipid peroxidation. However, the in vivo data to date are inconclusive, due in part to limitations in the methodologies. In this regard, our findings using the measurement of F(2)-isoprostanes, a reliable measure of in vivo lipid peroxidation and oxidant stress, do not support adverse effects of omega3 fatty acids on lipid peroxidation.     

Die Gefriertrocknung von Rinderkot

Fatty acids in fish can arise from two sources: synthesis de novo from non‐lipid carbon sources within the animal, or directly from dietary lipid. Acetyl‐CoA derived mainly from protein can be converted to saturated fatty acids via the combined action of acetyl‐CoA carboxylase and fatty acid synthetase. The actual rate of fatty acid synthesis de novo is inversely related to the level of lipid in the diet. Freshwater fish can de‐saturate endogenously‐synthesized fatty acids to monounsaturated fatty acids via a A9 desaturase but lack the necessary enzymes for complete de novo synthesis of polyunsaturated fatty acids which must therefore be obtained preformed from the diet. Most freshwater fish species can desaturate and elongate 18:2(n‐6) and 18:3(n‐3) to their C20 and C22 homologues but the pathways involved remain ill‐defined. Cyclooxygenase and lipoxygenase enzymes can convert C20 polyunsaturated fatty acids to a variety of eicosanoid products. The dietary ratio of (n‐3) to (n‐6) polyunsaturated fatty acids influences the pattern of eicosanoids formed. The ß‐oxidation of fatty acids can occur in both mitochondria and peroxisomes but mi‐tochondrial ß‐oxidation is quantitatively more important and can utilise a wide range of fatty acid substrates.     

Fish diet and physical fitness in relation to membrane and serum lipids, prostanoid metabolism and platelet aggregation in female students.

The effects of a 14-week fish diet and exercise programme on lipid metabolism and platelet aggregation in healthy female students (n = 99) were studied. The subjects were divided into four groups: a control group, a fish diet group (3.5 meals containing fish per week, 0.9 g n-3 fatty acids per day), an exercise group (at least three training sessions per week) and a combined fish diet and exercise group. The proportion of n-3 fatty acids increased at the expense of n-6 fatty acids in platelets and erythrocyte ghosts in the fish diet groups. Serum triglyceride concentrations tended to decrease in the fish diet and exercise groups and a significant decrease was found in the combined fish diet and exercise group (13%, P less than 0.05). No significant changes took place in the other serum lipid and apolipoprotein concentrations. Platelet production of thromboxane B2, plasma 6-keto-PGF1 alpha concentrations and adenosine 5'-diphosphate (ADP)-induced platelet aggregation also remained unchanged in all groups during the study. However, an inverse correlation was found between physical fitness (maximal oxygen uptake and maximal exercise intensity) and serum triglycerides, total cholesterol, low density lipoprotein cholesterol and platelet aggregation. This suggests that improved physical fitness is related to beneficial changes in serum lipid concentrations and to a decreased aggregation tendency of platelets. The responses of the female subjects to a fish diet were smaller when compared to earlier studies on male subjects. This suggests that there are sex differences in the efficiency of n-3 fatty acids in modifying lipid metabolism.     

Assessment of lipid and essential fatty acids requirements of black seabream (Spondyliosoma cantharus) by comparison of lipid composition in muscle and liver of wild and captive adult fish

The primary aim of the present study was to compare the contents of total lipid, lipid classes and their associated fatty acids in muscle and liver of wild and one-year captive black seabream (Spondyliosoma cantharus) adults, in order to elucidate the lipid and fatty acids requirements of this fish species of potential interest for aquaculture. The total lipid contents (TL) of muscle and liver of the captive fish were 2.5-fold greater than those of the wild fish. In consequence, contents of triacylglycerols were much higher in tissues of the captive fish. Distribution of fatty acids in total lipids and lipid classes of muscle and liver was also different between both groups of fish. For instance, percentages of 20:4n−6, 20:5n−6 and 22:6n−3 were considerably higher in the wild fish, whereas 18:1, 20:1, and 22:1n−9 as well as 18:2n−6 and 20:5n−3 were more abundant in the captive fish. These results suggest that the lipid composition of the commercial diet supplied to the captive black seabream differed greatly from that of the diet consumed by the fish in the wild, which hypothetically contains the desirable composition for the lipid nutrition of this fish species. Despite the good growth and survival achieved by the black seabream after one year in captivity, the significant accumulation of lipids and the imbalance of essential fatty acids in their muscle and livers, together with the absence of spawning, suggest that future research on the lipid requirements of this omnivorous species is necessary in order to establish whether the administration of currently available aquaculture formulated feeds is adequate for good black seabream performance and reproduction.