Freezing of herring (Clupea harengus) for human consumption is increasing in the Nordic herring industry, either onboard the fishing vessels or right after landing. The quality of frozen herring as a raw material does not only depend on the frozen storage conditions applied, but also on compositional features, something which in turn can vary with season and catching ground. To unravel the link between biological variations, basic muscle composition, and sensory properties of frozen herring, a unique herring raw material was caught by commercial fishing vessels at three locations: around Iceland, outside the Norwegian coast, and in Kattegat/Skagerrak. The samplings were done according to a specific scheme and conducted over several seasons and 2 years. The herring was converted into butterfly fillets, packed in cardboard boxes, frozen, and then stored at –20 °C or –80 °C for up to 18 mo. The sensory quality was characterized by objective sensory profiling. It was shown that two generalized sensory variables could be defined from a principal component analysis of the sensory data. Except for the expected pronounced effect from storage time, the most distinct variation followed the lipid content, which in turn varied with season. An unexpected conclusion was that catching location only had a minor affect on the changes in sensory quality of herring during frozen storage. Knowledge about how season and catching location affect herring during frozen storage will be useful for optimizing the utilization of herring for frozen storage for human consumption.
Flokkur: Greinar
High gene flow is considered the norm for most marine organisms and is expected to limit their ability to adapt to local environments. Few studies have directly compared the patterns of differentiation at neutral and selected gene loci in marine organisms. We analysed a transcriptome-derived panel of 281 SNPs in Atlantic herring (Clupea harengus), a highly migratory small pelagic fish, for elucidating neutral and selected genetic variation among populations and to identify candidate genes for environmental adaptation. We analysed 607 individuals from 18 spawning locations in the northeast Atlantic, including two temperature clines (5–12 °C) and two salinity clines (5–35‰). By combining genome scan and landscape genetic analyses, four genetically distinct groups of herring were identified: Baltic Sea, Baltic–North Sea transition area, North Sea/British Isles and North Atlantic; notably, samples exhibited divergent clustering patterns for neutral and selected loci. We found statistically strong evidence for divergent selection at 16 outlier loci on a global scale, and significant correlations with temperature and salinity at nine loci. On regional scales, we identified two outlier loci with parallel patterns across temperature clines and five loci associated with temperature in the North Sea/North Atlantic. Likewise, we found seven replicated outliers, of which five were significantly associated with low salinity across both salinity clines. Our results reveal a complex pattern of varying spatial genetic variation among outlier loci, likely reflecting adaptations to local environments. In addition to disclosing the fine scale of local adaptation in a highly vagile species, our data emphasize the need to preserve functionally important biodiversity.
The short and long term effects of short photoperiods on growth and maturity were investigated in 240 individually tagged juvenile Arctic charr (Salvelinus alpinus). The Arctic charr were reared at constant temperature (12 °C) and on four different light regimes; one group on continuous light (LD24:0) as control and three groups experienced a period of short day (LD8:16) on a three subsequent 6 week periods i.e. 24th September–6thNovember (LD8:16Sep–Nov), 6th November–19th December (LD8:16Nov–Dec), 19th December-29th January (LD8:16Dec–Jan). Before and after the short photoperiod treatment the groups were reared at continuous light. The growth of the fish was monitored over a period of 11 months. At the termination of the experiment in September 2009, the body mass of the three groups receiving a short day period (LD8:16 Sep–Nov, LD8:16 Nov–Dec and LD8:16 Dec–Jan) was significantly higher (13.9%, 12.9% and 10.7% respectively) than that of the group reared at continuous light (LD24:0). The three groups receiving the short photoperiod did not differ in weight at the end of the trial so the time of the year at which the short photoperiod was applied did not seem to be of importance regarding the growth enhancement. The maturation rate did not appear to be affected by the photoperiod treatments. The improved growth was mainly a result of a higher feed intake and improved feed conversion efficiency for the period following transfer of the charr from a short photoperiod to the continuous light. Application of such a winter photoperiod during the juvenile phase can, therefore, be used as a tool to increase the biomass and growth rate in Arctic charr farming.
Illegal, Unreported and Unregulated fishing has had a major role in the overexploitation of global fish populations. In response, international regulations have been imposed and many fisheries have been ‘eco-certified’ by consumer organizations, but methods for independent control of catch certificates and eco-labels are urgently needed. Here we show that, by using gene-associated single nucleotide polymorphisms, individual marine fish can be assigned back to population of origin with unprecedented high levels of precision. By applying high differentiation single nucleotide polymorphism assays, in four commercial marine fish, on a pan-European scale, we find 93–100% of individuals could be correctly assigned to origin in policy-driven case studies. We show how case-targeted single nucleotide polymorphism assays can be created and forensically validated, using a centrally maintained and publicly available database. Our results demonstrate how application of gene-associated markers will likely revolutionize origin assignment and become highly valuable tools for fighting illegal fishing and mislabelling worldwide.
The introduction of Next Generation Sequencing (NGS) has revolutionised population genetics, providing studies of non-model species with unprecedented genomic coverage, allowing evolutionary biologists to address questions previously far beyond the reach of available resources. Furthermore, the simple mutation model of Single Nucleotide Polymorphisms (SNPs) permits cost-effective high-throughput genotyping in thousands of individuals simultaneously. Genomic resources are scarce for the Atlantic herring (Clupea harengus), a small pelagic species that sustains high revenue fisheries. This paper details the development of 578 SNPs using a combined NGS and high-throughput genotyping approach. Eight individuals covering the species distribution in the eastern Atlantic were bar-coded and multiplexed into a single cDNA library and sequenced using the 454 GS FLX platform. SNP discovery was performed by de novo sequence clustering and contig assembly, followed by the mapping of reads against consensus contig sequences. Selection of candidate SNPs for genotyping was conducted using an in silico approach. SNP validation and genotyping were performed simultaneously using an Illumina 1,536 GoldenGate assay. Although the conversion rate of candidate SNPs in the genotyping assay cannot be predicted in advance, this approach has the potential to maximise cost and time efficiencies by avoiding expensive and time-consuming laboratory stages of SNP validation. Additionally, the in silico approach leads to lower ascertainment bias in the resulting SNP panel as marker selection is based only on the ability to design primers and the predicted presence of intron-exon boundaries. Consequently SNPs with a wider spectrum of minor allele frequencies (MAFs) will be genotyped in the final panel. The genomic resources presented here represent a valuable multi-purpose resource for developing informative marker panels for population discrimination, microarray development and for population genomic studies in the wild.+
The ethanol production capacity from sugars and lignocellulosic biomass hydrolysates by Thermoanaerobacter strain AK5 was studied in batch cultures. The strain converts various carbohydrates to acetate, ethanol, hydrogen, and carbon dioxide. Maximum ethanol yields on glucose and xylose were 1.70 and 1.35 mol (mol sugars)−1, respectively. Increased initial glucose concentration inhibited glucose degradation and end-product formation leveled off at 30 mM. Cultivation of the strain with decreased liquid–gas (L-G) ratios on glucose resulted in a shift to more acetate and less ethanol. End-product formation from glucose was further manipulated by adding extracellular electron acceptor (thiosulfate) or using a coculture of hydrogenotrophic methanogen. In both cases, the hydrogen-scavenging systems resulted in a dramatic shift from ethanol to acetate. Ethanol production from 4.5 g L–1 of complex biomass hydrolysates (grass, hemp, wheat straw, newspaper, and cellulose) pretreated with acid (0.50% H2SO4), alkali (0.50% NaOH), and without acid/alkali (control) and the enzymes Celluclast and Novozymes 188 (0.1 mL g–1 dry weight (dw); 70 and 25 U g–1 of Celluclast and Novozyme 188, respectively) was investigated. Highest ethanol yields (27.5 mM; 5.5 mM (g biomass)−1) were obtained on cellulose but lowest on hemp leafs (5.1 mM; 0.8 mM g–1). Chemical pretreatment increased ethanol yields substantially from lignocellulosic biomass but not from cellulose. The most-pronounced increase was on straw hydrolysates, where ethanol production increased from 5.5 mM to 15.2 mM on alkali-pretreated biomass. Ethanol yields were increased from 5.5 mM to 7.7 mM g–1 on cellulose by decreasing the hydrolysate concentration to 2.25 g L–1, because of incomplete glucose degradation in the higher-loaded system.
AsaP1 is a toxic aspzincin metalloendopeptidase secreted by the fish pathogen Aeromonas salmonicida subsp. achromogenes. The protease is highly immunogenic and antibodies against AsaP1 evoke a passive protection against infection with A. salmonicida subsp. achromogenes. The protease is expressed as 37 kDa pre-pro-protein and processed to an active enzyme of 19 kDa in A. salmonicida subsp. achromogenes. Recombinant expression of AsaP1rec in E. coli results in a protease of 22 kDa that is not secreted. AsaP1rec induces comparable pathological changes in Atlantic salmon (Salmo salar L.) to native AsaP1wt. The aim of the study was to construct AsaP1 toxoids by exchanging catalytically important amino acids in the active site region of the protease.
Four different AsaP1 mutants (AsaP1E294A, AsaP1E294Q, AsaP1Y309A, and AsaP1Y309F) were successfully constructed by one step site directed mutagenesis, expressed in E. coli BL21 C43 as pre-pro-proteins and purified by His-tag affinity chromatography and gel filtration. Three of the resulting mutants (AsaP1E294A, AsaP1E294Q, and AsaP1Y309A) were not caseinolytic active and are detected as unprocessed pre-pro-proteins of 37 kDa. Caseinolytic active AsaP1rec and a mutant with reduced activity, AsaP1Y309F, were processed to a size of 22 kDa. Furthermore, AsaP1rec is able to process the inactive mutants to the mature size of 22 kDa, allowing the conclusion that AsaP1 is autocatalytically processed.
All four mutants AsaP1E294A, AsaP1E294Q, AsaP1Y309A and AsaP1Y309F are non-toxic in fish but induce a specific anti-AsaP1 antibody response in Arctic charr (Salvelinus alpinus L.) and are therefore true toxoids and possible vaccine additives.
Lumpfish (Cyclopterus lumpus L. 1758) are widely distributed on both sides of the North Atlantic. They are a commercially important species, but stock size estimates have declined since the mid-1980s in Canada, Norway and Iceland. Little is known about the biology of this species, in particular the breeding migrations and population structure which are fundamental for effective management. This paper describes the development and characterization of twenty-two polymorphic microsatellite loci using next generation sequencing. The number of alleles per locus ranged from 3 to 27 in two geographically distant North Atlantic populations, with observed and expected heterozygosities ranging between 0.0625–0.979 and 0.0618–0.946, respectively. These loci are an important resource that will allow assessment of the population genetic structure of this species, and contribute to its appropriate management.
A thermophilic, aerobic, Gram-stain-negative, filamentous bacterium, strain PRI-4131T, was isolated from an intertidal hot spring in Isafjardardjup, NW Iceland. The strain grew chemo-organotrophically on various carbohydrates. The temperature range for growth was 40–65 °C (optimum 55 °C), the pH range was pH 6.5–9.0 (optimum pH 7.0) and the NaCl range was 0–3 % (w/v) (optimum 0.5 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain PRI-4131T represented a distinct lineage within the class Caldilineae of the phylum Chloroflexi. The highest levels of sequence similarity, about 91 %, were with Caldilinea aerophila STL-6-O1T and Caldilinea tarbellica D1-25-10-4T. Fermentative growth was not observed for strain PRI-4131T, which, in addition to other characteristics, distinguished it from the two Caldilinea species. Owing to both phylogenetic and phenotypic differences from the described members of the class Caldilineae , we propose to accommodate strain PRI-4131T in a novel species in a new genus, Litorilinea aerophila gen. nov., sp. nov. The type strain of Litorilinea aerophila is PRI-4131T ( = DSM 25763T = ATCC BAA-2444T).
This paper describes a quantitative risk–benefit assessment of fish consumption. We compare the net health effect expressed in DALYs of two scenarios. The reference scenario is the current fish intake of the Dutch population, which is less than what is recommended by the health authorities. The alternative scenario describes the health effects if the population consumes 200 g of fish per week, which is close to the recommendation. All health effects due to fish consumption for which there is convincing evidence are incorporated in the assessment. The QALIBRA software (www.qalibra.eu) is used to simulate the two scenarios. The results show there is a net benefit for the population if it consumes 200 g of fish each week.