Sea warming and fish distribution: the case of the small pelagic fish, Sardinella aurita, in the western Mediterranean

This study analyses the temporal and spatial changes in abundance and distribution of the warm water species round sardinella (Sardinella aurita) in the western Mediterranean over the last decades in relation to sea water temperature. In the western Mediterranean basin (1950–2003), a significant positive relationship was found between round sardinella landings and temperature anomalies. Along a latitudinal gradient off the Mediterranean Iberian coast (1989–2004), a gradual increase in species abundance was observed from south to north, with a certain time lag going northwards, associated with the increase in sea water temperature. The abundance of round sardinella in the two warmest and southernmost areas was positively and significantly correlated with sea surface temperature registered during the start of gonad maturation the previous year. In addition, the positive relationship established between water temperature and abundance of round sardinella in the coldest and northernmost study area demonstrates that there is a temperature limit for the distribution of this species in the western Mediterranean. In addition, this study analyses round sardinella larvae distribution and abundance in the summers of 2003 and 2004, and conducts a comparison with the situation 20 years ago (summer 1983). Results show a marked increase in larval abundance during the last decades and the present appearance of larvae in the northernmost study areas, where they did not occur 20 years ago. This indicates the successful reproduction of round sardinella in the northern part of the Mediterranean, where the species has expanded, confirming its establishment in the area.     

Nutritional Composition and heavy Metal Concentrations in Sardinella maderensis (Lowe, 1838) obtained from the Mauritanian fisheries

This study attempts to delineate the nutritional value and potential problem of toxic metal contamination in Sardinella maderensis (Lowe,1838) originating from Mauritanian fishery destined for regional common human consumption. Samples caught in Mauritania were delivered to Turkey by ship in 22 days in cold storage. Amino acids, fatty acids and toxic metal analyses of the samples were carried out by using a HPLC (High Performance Liquid Chromatograph), GC (Gas Chromatography) and a ICP-MS (Inductively Coupled Plasma-Mass Spectrometry), respectively. Overall, the range of total Saturated Fatty Acids (SFAs), Monounsaturated Fatty Acids (MUFAs) and Polyunsaturated Fatty Acids (PUFAs) were found to be 34.35%, 28.13% and 34.50%, respectively. In terms of Eicosapentaenoic acid (EPA)+Docosahexaenoic acid (DHA) levels were found to be in total 24.34%. Amino acids content such as glutamic acid, histidine, leucine and lysine were 1735.5, 1,409, 1,580 and 1,710.5 mg/100 g tissue, respectively. Toxic metal levels of Hg, Cd, As, Cr, Mn, Co were determined to reach values between 0.03–4.19 mg/kg. Athough the study is limited, it seems that results on the composition of fatty acids and amino acid, indicate the high nutritional value, well suited for human consumption in particular in terms of omega 3 and essential amino acids.     

Trophic niche overlap between round sardinella (Sardinella aurita) and sympatric pelagic fish species in the Western Mediterranean

The northward expansion of round sardinella (Sardinella aurita) in the Mediterranean Sea, together with declines and fluctuations in biomass and landings of European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) observed in recent decades, may suggest potential inter‐specific competition in the pelagic domain. The coexistence of sympatric zooplanktivorous fish species might therefore be exposed in part to trophic niche overlap and competition for food. Combining visual diet characterization under the microscope with DNA metabarcoding from stomach contents of fish collected in spring results show that predation on relatively large krill is equally important for sardinella than for the other two niche overlapping species. Furthermore, an important overlap is found in their isotopic niche, especially with anchovy, using nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotopes in muscle tissue. In fact, the three fish species are able to feed effectively in the whole prey size spectrum available during the sampled season, from the smallest diatoms and copepods to the larger prey (i.e., decapods and euphausiids), including fish larvae. Moreover, effective predation upon other large prey like siphonophores, which is observed only when multi‐proxy analyses in stomach contents are applied, might also be relevant in the diet of sardinella. The overlapping diet composition in spring, together with the effective use of food resource by sardinella, can be of special interest in potential future scenarios with warmer water temperature leading to lower zooplankton and/or higher jellyfish availability, where sardinella may take advantage over other species due to its feeding plasticity.     

Genetic relationship of Sardinella lemuru from lombok strait with fish rich in omega-3 fatty acid

Lombok Strait has abundance of Sardine, Sardinella lemuru, which contains such high amount of omega-3 fatty acid (omega-3). However, the genetic relationship of S. lemuru with other commercial fish rich in omega-3 has not been widely studied yet. Studies on genetic proximity of S. lemuru with the other marine fish using 12S rRNA gene is very important in order to obtain genetic information of the Sardine to develop an appropriate strategy for future conservation of the fish in Lombok Strait. The aim of this study was to find out the genetic relationship of Sardinella lemuru living in Lombok Strait with the economically valuable fish and its correlation with omega-3 production. Sardinella lemuru were collected from Lombok Strait, the phylogenetic tree was done based on 12S rRNA gene through a neighbor-joining method to identify the relationship of Sardines and fish rich in omega-3 fatty acid. The phylogenetic tree showed that Sardinella lemuru is similar to Sardinella aurita and has a close similarity with Sardinella maderensis. However, the relationship did not correspond to omega-3 production. Based on the results of the study, it is suggested that the production of omega-3 is not specifically based on the proximity of the species, but it is more associated with conserved domain of Δ6-desaturase. Nevertheless, detailed mechanisms still need to be elucidated.     

Lipids and fatty acids of the southwestern corn borer,Diatraea grandiosella

The lipids of the adults and of several immature stages of the southwestern corn borer, Diatraea grandiosella, were studied after they were fed natural corn stalks or artificial diets. Linoleic acid (18:2) was the major fatty acid of the neutral lipids in both the natural and the artificial diets, but aleic acid (18:1) was the principal neutral lipid in all insect stages. Also, linoleic acid and oleic acid were the principal acids in the insect phospholipids of all stages. The content of linoleic acid in the natural diet was also high, but that in the artificial diet appeared to be much too low for insect requirements. Phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were the major phospholipids in all growth stages. Thus, in larvae diapausing in the field, the unsaturated fatty acid content of PC was 59·3 per cent, primarily 16:1 and 18:1, and PE was 87·4 per cent, primarily 18:1, 18:2, and 18:3, and the fatty acids in the number 1- and 2-positions of PC were 53·6 and 97·2 per cent unsaturated, respectively. The haemolymph of diapausing southwestern corn borer larvae contained primarily glycerides but also had some PC and PE. Fat body from diapausing larvae contained primarily 16:0, 16:1, and 18:1 in a ratio of 1 : 1 : 2. Thus lipids of the southwestern corn borer do not reflect dietary lipids as closely as do other insects studied.     

Lipids and fatty acids in cellulosomes of Clostridium thermocellum

A lipid component was found in cellulosomes (multienzymatic cellulase complexes) of the thermophilic bacterium Clostridium thermocellum. Two major fractions of the cellulosomes have been studied, one with a relative molecular mass (M_r) of 10–50 million (polycellulosomes, fraction A) and the other with an M_r 0.5–10 million (fraction B) It was found that the larger cellulosomes contained higher relative amounts of lipids (8.1%) as well as Ca²⁺ ions (0.6%), and showed higher cellulolytic activity Among the lipids was cardiolipin, 1,2- and 1,3-diglycerides, triglycerides, and up to 11 free fatty acids, including both saturated (palmitic, lauric, myristic, pentadecanoic, stearic, arachinic) and unsaturated (myristoleic, palmitoleic, and oleic) moieies Cardiolipin was a major phospholipid component in cellulosomes and was also found to be a major phospholipid component of the cell membrane, palmitic acid was a major fatty acid Fraction B contained less fatty acids (0.5% vs 1.27% in fraction A) with fewer acids detected than in fraction A Removal of the extractable lipids led to fragmentation of the cellulosomes with a concurrent sharp drop in their enzymatic activity Total removal of the lipids from cellulosomes was possible only when the proteins were completely denatured The qualitative composition of the extractable and non-extractable fatty acids was the same The lipid component of the cellulosomes, containing a high content of the unsaturated fatty acids, was located mainly in the part of cellulosomes that is in tight contact with the cellulose surface, and it apparently plays an important role in the tight adsorption of the cellulosomes on cellulose.     

Activation of an alkaline proteinase from fish skeletal muscle by fatty acids and sodium dodecyl sulphate

1. Fish skeletal muscle contains an alkaline thiol proteinase with a temperature optimum of 60 degrees C and undetectable activity below 50 degrees C. 2. The present study shows that fatty acids and sodium dodecyl sulphate (SDS) shifted the temperature-activity curve of the enzyme toward the lower temperature side. 3. All unsaturated fatty acids tested strongly stimulated proteolytic activity at 37 degrees C, whereas myristic acid was the only saturated fatty acid that produced an important degree of activation. 4. These effects could be observed at millimolar concentrations of the reagents.     

Reproductive cycle of gilt sardine,Sardinella aurita,Valenciennes 1847, in the eastern middle Adriatic Sea

The annual reproduction cycle of gilt sardine, Sardinella aurita, based on gonad maturity stages, gonad weight and gonadosomatic index was the subject of this study. A total of 2033 gilt sardines (983 males, 1021 females and 29 undetermined) were analysed. Fish were collected monthly from commercial purse seiners between November 2007 and January 2009 in the eastern middle Adriatic Sea (mesh size 8 mm/bar length/; sampling: five boats per month). Based on the monthly evolution of gonad maturation stages, gonad weights and gonadosomatic index, the peak spawning season was determined to be from June to August. Variations in sea surface temperature (SST) coincided with monthly variations of the gonadosomatic index. Highest monthly average values for both analysed parameters were recorded in July (GSI = 3.38; T = 26.5°C). Fifty per cent (L₅₀) of males and females reached sexual maturity at TL 15.8 cm and at 16.6 cm, respectively. Absolute fecundity ranged from 8458 to 48 032 (mean 34 565 ± 10 310), whereas relative fecundity was from 171 to 722 (mean 385 ± 104.35). Mean value of the oocyte size was 0.53 ± 0.10 mm.     

Tissue expression of three structurally different fatty acid binding proteins from rat heart muscle, liver, and intestine

Three structurally different 14-15 kDa fatty acid binding proteins have have been purified from rat liver, small intestinal epithelium, and heart muscle, and were quantitated using specific antisera in rat tissues. Heart muscle fatty acid binding protein comprised 5% of heart muscle cytosol protein and was also expressed in stomach, muscle, testis, ovary, kidney, brain, and adipose tissue, a pattern distinct from both liver protein (expressed in liver, small and large intestinal epithelium, and adipose tissue) and intestinal protein (expressed in small and large intestinal epithelium and stomach). Distinctive patterns of tissue expression of the three different fatty acid binding proteins suggest that they may perform different specific functions in fatty acid transport and metabolism.     

Sterols and fatty acids from three species of mangrove

The hydrolysis of steryl esters on thin-layer chromatographic plates by porcine pancreatic lipase is described. The sterols and fatty acids produced were separated on the same plate, recovered, and analysed by gas-liquid chromatography for their compositions. Synthetic cholesteryl esters containing various saturated and unsaturated fatty acids and synthetic steryl oleates with various sterols were lipolysed along with steryl esters of Acanthus ilicifolius, Bruguiera gymnorhiza and Rhizophora mucronata mangrove leaves. The major sterol was sitosterol which was accompanied by cholesterol, campesterol, stigmasterol and 28-isofucosterol. In addition, stigmast-7-en-3β-ol was present in R. mucronata leaves. The component fatty acids found in all three species were 16:0, 18:0, 18:1, 18:2 and 18:3. The relative proportions of the sterols and fatty acids were significantly different from the chemotaxonomic standpoint. The results obtained by carrying out plate lipolysis for 45 min at 40° compared well with those produced by conventional chemical hydrolysis.     

The link between migration, the reproductive cycle and condition of Sardinella aurita off Mauritania, north-west Africa

The annual migration pattern of round sardinella Sardinella aurita up and down the north-western African coast between 12° N (Senegal) and 22° N (western Sahara) was shown to be associated with spawning activity and a distinct seasonality in fish condition, based on monthly sampling from commercial catches (2000–2003). Some S. aurita were found to spawn throughout the entire year, but a peak in spawning existed during the summer (June to September). The spawning cycle is apparent from seasonality in maturity stages, but is also demonstrated by the increase in gonad mass and fat content of the fish in springtime, the period preceding spawning. During the months after spawning, although feeding is maintained, the physical condition of the fish collapses, and fat content rapidly declines.     

Lipids and fatty acids in ice algae and phytoplankton from the Marginal Ice Zone in the Barents Sea

Samples of ice algae from the Marginal Ice Zone in the Barents Sea could be divided into two categories: one dominated by assemblages of Melosira arctica, and the other dominated by Nitzschia frigida and associated diatoms. Total lipid from the Melosira assemblages consisted of approximately equal amounts of polar lipids and triacylglycerols. Total lipid from the Nitzschia assemblages contained more triacylglycerols than polar lipids. Total lipid from the Melosira assemblages had higher percentages of C16 PUFA, especially 16:4(n-1) and 20:5(n-3), than that from the Nitzschia assemblages, this reflecting the higher percentages of both C16 PUFA and 20:5(n-3) in polar lipids than in triacylglycerols. Phytoplankton from the pelagic zone were␣richer in flagellates and contained less C16 PUFA and 20:5(n-3) but more C18 PUFA and 22:6(n-3). The dominance of diatoms in the ice-algae assemblages in the Marginal Ice Zone and their high nutritional value as a source of 20:5(n-3) for higher trophic levels are emphasised. Received: 24 November 1997 / Accepted: 8 February 1998     

Seasonal composition of lipids, fatty acids, and sterols in the edible red alga Grateloupia turuturu

Composition of lipids, sterols, fatty acids (FA), and phospholipids in the edible Rhodophyta Grateloupia turuturu from Britanny, France, was investigated over four seasons in order to identify compounds with potential benefits in health and nutrition. The lipid content was found to vary from 3.3 to 4.1 % dry weight. No marked variations were observed for glycolipids accounting for 42.3–46.8 %, whereas neutral lipids and phospholipids fluctuated from 20.1 % (summer) to 41.8 % (winter), and 11.2 % (winter) to 33.4 % (summer), respectively. Polyunsaturated FA of the total lipids were found from 20.4 % (winter) to 31.1 % (summer), including 20:5 ω3 acid as the major one (up to 16.3 % in summer). Phosphatidylcholine (20.0–43.7 %) and phosphatidylserine (24.6–37.5 %) were the dominant phospholipids in all seasons. Compounds of interest were identified in minor amounts such as squalene, α-tocopherol, phytonadione (vitamin K₁), cholesteryl formate, cholest-4-en-3-one, and cholesta-4,6-dien-3-one. Cholesterol was the major sterol with a lower content in spring and summer.