Merki: Composition

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Discriminating populations of Atlantic herring mixing in the Norwegian Sea feeding ground using single nucleotide polymorphisms (SNPs)

Atlantic herring Clupea harengus feeding in the Norwegian Sea are assumed to consist of Norwegian spring spawners (NSSH), Icelandic summer spawners (ISSH) and North Sea autumn spawners (NSAH). Putative Norwegian autumn spawners (NASH), Faroese autumn (FASH) and spring (FSSH) spawners also feed in the area.

However, until there is a method to discriminate between populations in mixed samples, fishery and survey data from the Norwegian Sea will be solely attributed to the predominating NSSH, ultimately causing biased stock assessments.

Hence, we evaluated if a panel of 120 single nucleotide polymorphisms (SNPs) associated with spawning characteristics and salinity preferences would be an effective discrimination tool. The overall observed levels of genetic differentiation were high (FST = 0.57, p < 0.001, 95% CI: 0.51−0.62). Spawners from stocks under current management (NSSH, NSAH and ISSH) were well separated, but the putative populations were not. Discriminant analysis of principal component as well as Structure runs confirmed the differentiation observed with FST. When the SNP panels were tested on commercial fishery samples of NSSH east of Iceland, up to 16% were assigned to ISSH.

This implies that catch data are seriously biased and demonstrates the potential of SNP panels as a tool to solve the problem. However, work is needed to develop improved SNP panels that effectively separate the putative populations from the managed stocks. We recommend that such a tool should be established in regular sampling of fishery and surveys in the Norwegian Sea and accounted for in future stock assessments, advice and management.

Skýrslur

Seasonal and geographical variation in chemical composition and lipid stability of Atlantic mackerel (Scomber scombrus) caught in Icelandic waters

Útgefið:

01/12/2015

Höfundar:

Paulina E. Romotowska, Magnea G. Karlsdóttir, María Guðjónsdóttir, Sigurjón Arason, Hörður G. Kristinsson

Styrkt af:

AVS rannsóknasjóður í sjávarútvegi (R 040-12)

Tengiliður

Sigurjón Arason

Yfirverkfræðingur

sigurjon.arason@matis.is

Seasonal and geographical variation in chemical composition and lipid stability of Atlantic mackerel (Scomber scombrus) caught in Icelandic waters

Á þeim tíma sem makríll er við íslandsstrendur er hann í miklu æti sem veldur því að hann snögg fitnar með þeim afleiðingum að holdið verður mjög viðkvæmt fyrir meðhöndlun. Í þessari rannsókn var makríll sem var veiddur sumarvertíðarnar 2012 og 2013 (júlí, ágúst, september) og frá mismunandi veiðisvæðum (austur, norðaustur, suður og suðaustur) skoðaður. Til þess að meta á hversu vel hráefnið hentar til vinnslu á hágæðaafurðum til manneldis, var makríllinn mældur m.t.t. vatns- og fituinnihalds, fitusýrusamsetningar, litar, þránunar og frírra fitusýra. Almennt var makríllinn sem safnað var sumarið 2012 af betri gæðum en makríll frá 2013. Niðurstöðurnar gáfu einnig til kynna breytileika á milli veiðimánaða m.t.t. fituinnihalds og framgang þránunar. Makríll sem var veiddur um miðbik vertíðarinnar hafði lægsta þránunargildið, sem gefur til kynna að sá makríll hentar best fyrir vinnslu á hágæðaafurðum til manneldis.

Atlantic mackerel (Scomber scombrus) appears in Icelandic waters during its heavy feeding period, resulting in variation in mackerel products quality. Fish caught at different season during the summers of 2012 and 2013 (July, August, September) and at different sites of the Icelandic fishing area (East, Northeast, South and Southeast) were analysed. Measurements of lipid and water content, fatty acid composition, colour changes, lipid hydroperoxide (PV), thiobarbituric reactive substances (TBARS) and free fatty acid (FFA) were studied with the aim of investigating whether this raw material was suitable for the production of high quality products for human consumption. In general, samples collected during the summer of 2012 showed a better condition than fish from 2013. The results indicated seasonal variation in lipid content and rancidity development. The lowest rancidity values were observed in the middle of the Icelandic catching season, indicating that this raw material was best suited for production of high quality products. Moreover, geographical variation of the mackerel catches had an impact on the saturation of the fatty acids, and appeared as follows: East > Southeast > Northeast > South.

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Skýrslur

Áhrif þurrkaðferða á eiginleika sölva / Influence of drying methods on the properties of dulse

Útgefið:

01/06/2011

Höfundar:

Þóra Valsdóttir, Irek Klonowski

Styrkt af:

AVS

Tengiliður

Þóra Valsdóttir

Verkefnastjóri

thora.valsdottir@matis.is

Áhrif þurrkaðferða á eiginleika sölva / Influence of drying methods on the properties of dulse

Þekking á breytum sem stýra gæðum og eiginleikum þurrkaðra sölva (Palmaria palmata) er tiltölulega lítil og á fárra vitorði. Ef auka á nýtingu og breikka notkunarmöguleika á sölvum er mikilvægt er að rannsaka nánar þessar breytur og skjalfesta þær. Þessi skýrsla greinir frá niðurstöðum tilrauna sem höfðu það að meginmarkmiði að bera saman áhrif þriggja ólíkra þurrkaðferða á næringargildi og eðliseiginleika þurrkaðra sölva. Þurrkunaraðferðirnar sem voru bornar saman voru sólþurrkun, ofnþurrkun og frostþurrkun auk þess að áhrif verkunar á sólþurrkuðu sölin voru metin. Sambærilegar breytingar mældust á næringarefnum eftir þurrkaðferð. Helsti munur m.t.t. þurrkaðferða greindist í magni C-vítamíns. Þá var sjáanlegur munur á lit og áferð. Bragðeiginleikar voru ekki mældir en talið er að einhvern mun sé þar að finna. Þrátt fyrir að niðurstöðurnar hafi gefið ákveðin svör þá vöknuðu margar spurningar við túlkun á þeim. Þörf er því talin á því að afla meiri þekkingar á eiginleikum sölva og samspili þeirra við mismunandi vinnsluþætti.

The influence of three different drying methods on selected nutritional and physiochemical properties of dulse were compared; sun drying, oven drying and freeze drying. Similar influence was found on nutritional components. The main difference was found on C-vitamin retention. Difference was found as well in colour and texture. Flavour characteristics were not analysed, however some differences are expected. Despite giving some answers, the results raised many questions on their interpretation. There is a need for extended knowledge on the properties of dulse and their interplay with different processing parameters.

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