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Probalistic models for harmful algae: application to the Norwegian coast
Get PDFWe have developed probabilistic models to estimate the likelihood of harmful algae presence and outbreaks along the Norwegian coast, which can help optimization of the national monitoring program and the planning of mitigation actions. We employ support vector machines to calibrate probabilistic models for estimating the presence and harmful abundance (HA) of eight toxic algae found along the Norwegian coast, including Alexandrium spp., Alexandrium tamarense, Dinophysis acuta, Dinophysis acuminata, Dinophysis norvegica, Pseudo-nitzschia spp., Protoceratium reticulatum, and Azadinium spinosum. The inputs are sea surface temperature, photosynthetically active radiation, mixed layer depth, and sea surface salinity. The probabilistic models are trained with data from 2006 to 2013 and tested with data from 2014 to 2019. The presence models demonstrate good statistical performance across all taxa, with R (observed presence frequency vs. predicted probability) ranging from 0.69 to 0.98 and root mean squared error ranging from 0.84% to 7.84%. Predicting the probability of HA is more challenging, and the HA models only reach skill with four taxa (Alexandrium spp., A. tamarense, D. acuta, and A. spinosum). There are large differences in seasonal and geographical variability and sensitivity to the model input of different taxa, which are presented and discussed. The models estimate geographical regions and periods with relatively higher risk of toxic species presence and HA, and might optimize the harmful algae monitoring. The method can be extended to other regions as it relies only on remote sensing and model data as input and running national programs of toxic algae monitoring.publishedVersio
Understanding size selectivity of trawls using structural models: Methodology and a case study on fish sorting grids
Get PDFFish behaviour affects the performance of selection devices in fishing gears. Traditionally, fish behaviour in relation to selection devices is assessed by direct observation. However, this approach has limitations, and the observations are not explicitly incorporated in the selectivity models. Further, underwater observations and quantification of fish behaviour can be challenging. In this study we outline and use an indirect method to explicitly incorporate and quantify fish behaviour in trawl selectivity analysis. We use a set of structural models, which are based on modelling the actual processes believed to determine the size selection of the device, to discern which behaviours are most likely to explain the selectivity process. By bootstrapping we assess how confident we can be in the choice of a specific structural model and on discerning the associated behavioural aspects. We collected size selectivity data in the Barents Sea demersal trawl fishery targeting gadoids, where the use of a sorting grid is compulsory. Using our modelling approach, we obtained deeper understanding of which behavioural processes most likely affect size selectivity in the sorting grids tested. Our approach can be applied to other fishing gears to understand and quantify fish behaviour in relation to size selectivity.publishedVersio
Bestandsvurdering av kveite (Hippoglossus hippoglossus) i Norsk økonomisk sone (ICES-områder 1-4) i 2024
Get PDFKveite (Hippoglossus hippoglossus) er en langtlevende flatfiskart med lang fiskerihistorie og høy økonomisk og kulturell verdi i Norge. Arten forekommer over store områder i norske farvann, men hovedtyngden av bestanden antas nå å være i fjorder og kystnære områder langs norskekysten, og anses derfor som en norsk bestand. Bestanden er delt inn i to forvaltningsenheter, sør og nord for 62°N basert på fisket, antatt bestandsutvikling og tilgjengelig data (tidsserier) til bruk i bestandsvurdering. Etter en kollaps i hele utbredelsesområdet på 1970-tallet, har rapporterte landinger nord for 62°N økt, spesielt i perioden etter 1995. Samme økning i rapporterte landinger er ikke observert i området sør for 62°N. Det er antatt at endringer i landinger over tid er en kombinasjon av endring i bestandsstørrelse og fiskeinnsats. For tiden, er fisket bare begrenset av redskapsreguleringer (antall kroker, antall garn og maskevidde i garn), fredningstid for direktefiske samt minstemål og maksmål. Det har vist seg å være vanskelig å begrense innsatsen i fisket da stadig flere fartøy deltar, fartøyene øker bruksmengden (flere garn/kroker) og de bruker mer effektive redskaper (trommelline). For å unngå overfiske er det derfor etter Havforskningsinstituttets vurdering, behov for en forskningsbasert overvåking, modelbasert bestandsvurdering og tilhørende kvoteråd. Mangel på aldersdata (spesielt fra fangst) og andre biologiske parametere begrenser hvilke modeller som kan benyttes. Basert på tilgjengelige data og kunnskap ble det bestemt at en biomassemodell er den beste tilnærmingen for en bestandsvurdering av kveitebestanden på det nåværende tidspunktet. Bestandsmodellen har blitt implementert i modelleringsrammeverket SPiCT, som er en foretrukket biomassemodell i ICES. Etter en omfattende gjennomgang av alle relevante tokt- og fiskeridata som kunne inneholde informasjon om endringer i bestanden, ble SPiCT testet med forskjellige kombinasjoner av bestandsindekser og konfigureringer. Datatilgang, fangstutvikling og antatt bestandsutvikling i området sør for 62°N er så forskjellig fra nord for 62°N at dette området ikke inngår i modelleringen. Rapporten presenterer derfor modellkonfigurasjonen for kveite nord for 62°N, som etter analysene anses å være den best egnete gitt den nåværende data- og kunnskapsstatus. Resultatet viser at bestandsmodellen kan aksepteres og brukes til å lage et råd for totalfangst (TAC) av kveite nord for 62°N. Videre diskuteres ytterlige data- og kunnskapsbehov, særlig angående fritids- og turistfisket.Bestandsvurdering av kveite (Hippoglossus hippoglossus) i Norsk økonomisk sone (ICES-områder 1-4) i 2024publishedVersio
Fordeling og mengde av tobis i norsk sone av Nordsjøen i mai 2023 — Tobistokt i Nordsjøen 23. april – 13. mai 2023
Get PDFGytebiomassen i 2023 av havsil (tobis) i sørlige del av norsk sone av Nordsjøen er 105 000 tonn (5%-95% konfidensintervall er 80 000 – 136 000 tonn), og er sterkt redusert siden toppåret 2020. Middels og dårlig rekruttering etter 2019 er hovedårsaken til denne nedgangen, men i tillegg er individvekten per aldersgruppe i 2023 mellom 31% og 43% lavere enn langtidsgjennomsnittet for perioden 2009-2022. De tre siste årene har det vært store forekomster av hvitting og spesielt hyse i tobisområdene, og toktresultatene tyder på at beitetrykket på tobis er vesentlig høyere enn tidligere. Mange eldre individer med alder 4 og høyere av tobis i forvaltningsområdene 1-3 tyder på at fisketrykket har vært moderat. I de to nordligste forvaltningsområdene 4 og 5 er biomassen vurdert til å være kritisk lav, mens den er vesentlig sterkere i de sørlige forvaltningsområdene 1, 2 og 3. Under toktet i 2023 ble biomassen estimert til 64 tonn (5%-95% konfidensintervall er 33 – 100 tonn) i forvaltningsområde 5 (Vikingbanken), og dette er det laveste estimatet i tidsserien 2009-2023.Fordeling og mengde av tobis i norsk sone av Nordsjøen i mai 2023 — Tobistokt i Nordsjøen 23. april – 13. mai 2023publishedVersio
The surveillance and control program for bonamiosis and marteiliosis in European flat oysters, Ostrea edulis in 2023
Get PDFThe surveillance program for the molluscan diseases bonamiosis and marteiliosis is carried out by the Institute of Marine Research according to a contract with the Norwegian Food Safety Authority. In 2023, flat oysters were sampled from four locations: A breed poll where oyster spat is produced, an abandoned breed poll where oyster spat was previously produced, and two fjord systems with larger populations of flat oysters. Samples were collected in April – June and September, to be able to detect Bonamia sp. and Marteilia sp. during the periods when the potential prevalence is highest. No abnormal mortalities were observed during the surveillance. Bonamia ostreae / B. exitiosa and Marteilia refringens were not detected. Marteilia refringens Type O and M are now divided into two species; Marteilia refringens in flat oysters and M. pararefringens in blue mussels. Blue mussels are therefore no longer considered susceptible hosts for M. refringens, but our research project shows that the related Marteilia pararefringens is widespread in certain mussel populations along the South and West coasts of Norway. M. pararefringens can have a serious impact on blue mussel populations, and consideration should be given to listing the parasite on a national list. Furthermore, we propose a formal application for disease free status for Bonamia spp. and Marteilia refringens in Norwegian flat oystersThe surveillance and control program for bonamiosis and marteiliosis in European flat oysters, Ostrea edulis in 2023publishedVersio
The impact of short-term eucaloric low- and high-carbohydrate diets on liver triacylglycerol content in males with overweight and obesity: a randomized crossover study
Get PDFBackground Intrahepatic triacylglycerol (liver TG) content is associated with hepatic insulin resistance and dyslipidemia. Liver TG content can be modulated within days under hypocaloric conditions. Objectives We hypothesized that 4 d of eucaloric low-carbohydrate/high-fat (LC) intake would decrease liver TG content, whereas a high-carbohydrate/low-fat (HC) intake would increase liver TG content, and further that alterations in liver TG would be linked to dynamic changes in hepatic glucose and lipid metabolism. Methods A randomized crossover trial in males with 4 d + 4 d of LC and HC, respectively, with ≥2 wk of washout. 1H-magnetic resonance spectroscopy (1H-MRS) was used to measure liver TG content, with metabolic testing before and after intake of an LC diet (11E% carbohydrate corresponding to 102 ± 12 {mean ± standard deviation [SD]) g/d, 70E% fat} and an HC diet (65E% carbohydrate corresponding to 537 ± 56 g/d, 16E% fat). Stable [6,6-2H2]-glucose and [1,1,2,3,3-D5]-glycerol tracer infusions combined with hyperinsulinemic-euglycemic clamps and indirect calorimetry were used to measure rates of hepatic glucose production and lipolysis, whole-body insulin sensitivity and substrate oxidation.publishedVersio
Loss of bmp15 function in the seasonal spawner Atlantic salmon results in ovulatory failure
No full textBone morphogenetic protein 15 (BMP15) is an oocyte-specific growth factor important for successful female reproduction in mammals. While mutations in BMP15/Bmp15 cause ovulatory deficiency and/or infertility in certain mammalian species, loss of bmp15 in zebrafish, a continuous spawner and the only bmp15 knockout model in fish to date, results in complete arrest of follicle development and later female-to-male sex reversal, preventing to examine effects on ovulation/fertilization. Here, we used Atlantic salmon, a seasonal spawner, and generated bmp15 mutants to investigate ovarian development and fertility. Histological and morphometric analyses revealed that in biallelic frameshift (bmp15 fs/fs) mutant ovaries, folliculogenesis started earlier, resulting in an advanced development compared to wild-type (WT) controls, accompanied by a weaker expression of the (early) oocyte-specific factor figla. This precocious ovarian development was followed in bmp15 fs/fs females by enhanced follicle atresia during vitellogenic stages. Although genes involved in steroid synthesis and signaling (star, cyp11b, cyp17a1 and esr1) were dramatically higher in late vitellogenic bmp15 fs/fs mutant ovaries, estradiol-17β plasma levels were lower than in WT counterparts, potentially reflecting compensatory changes at the level of ovarian gene expression. At spawning, bmp15 fs/fs females displayed lower gonado-somatic index values and reduced oocyte diameter, and the majority (71.4%), showed mature non-ovulating ovaries with a high degree of atresia. The remaining (28.6%) females spawned eggs but they either could not be fertilized or, upon fertilization, showed severe malformations and embryonic mortality. Our results show that Bmp15 is required for proper follicle recruitment and growth and later ovulatory success in Atlantic salmon, providing an alternative candidate target to induce sterility in farmed salmon. Moreover, since loss of bmp15 in salmon, in contrast to zebrafish, does not result in female-to-male sex change, this is the first mutant model in fish allowing further investigations on Bmp15-mediated functions in the ovulatory period.publishedVersio
Global impacts of marine heatwaves on coastal foundation species
Get PDFWith increasingly intense marine heatwaves affecting nearshore regions, foundation species are coming under increasing stress. To better understand their impacts, we examine responses of critical, habitat-forming foundation species (macroalgae, seagrass, corals) to marine heatwaves in 1322 shallow coastal areas located across 85 marine ecoregions. We find compelling evidence that intense, summer marine heatwaves play a significant role in the decline of foundation species globally. Critically, detrimental effects increase towards species warm-range edges and over time. We also identify several ecoregions where foundation species don’t respond to marine heatwaves, suggestive of some resilience to warming events. Cumulative marine heatwave intensity, absolute temperature, and location within a species’ range are key factors mediating impacts. Our results suggest many coastal ecosystems are losing foundation species, potentially impacting associated biodiversity, ecological function, and ecosystem services provision. Understanding relationships between marine heatwaves and foundation species offers the potential to predict impacts that are critical for developing management and adaptation approaches.publishedVersio
Reef Adapt: A tool to inform climate-smart marine restoration and management decisions
Get PDFA critical component of ecosystem restoration projects involves using genetic data to select source material that will enhance success under current and future climates. However, the complexity and expense of applying genetic data is a barrier to its use outside of specialised scientific contexts. To help overcome this barrier, we developed Reef Adapt (www.reefadapt.org), an innovative, globally applicable and expandable web platform that incorporates genetic, biophysical and environmental prediction data into marine restoration and assisted gene flow planning. The Reef Adapt tool provides maps that identify areas with populations suited to user-specified restoration/recipient sites under current and future climate scenarios. We demonstrate its versatility and practicality with four case studies of ecologically and evolutionarily diverse taxa: the habitat-forming corals Pocillopora damicornis and Acropora kenti, and macroalgae Phyllospora comosa and Ecklonia radiata. Reef Adapt is a management-ready tool to aid restoration and conservation efforts amidst ongoing habitat degradation and climate change.publishedVersio
Exploring cohort-based density-dependent effects on maturity in Norwegian spring-spawning herring (Clupea harengus)
Get PDFThe influence of density-dependent effects on fish maturity is rarely considered when evaluating different harvest strategies, nor when formulating short-term catch advice. In cases where these effects are included, the spawning stock size is commonly used as the density variable. However, this approach is inadequate for a stock where juvenile and mature individuals have limited interaction. In such instances, using the abundance of the recruits of a cohort as a density variable is a more appropriate alternative. In this study, we have used the Norwegian spring-spawning herring (Clupea harengus) as a test stock to investigate this concept and develop a model for predicting future trends in maturity-at-age. This stock is an optimal candidate since previous publications have highlighted a spatial separation between juveniles and adults, and changes in maturity in response to historical stock dynamics have been observed and documented. Our approach provides increased accuracy for predicting maturity-at-age when compared to an assumption of density independence. Furthermore, a further expansion of this approach, i.e. applying a relationship with somatic growth, can contribute to more realistic simulations for predicting future stock dynamics, and more appropriate catch advice.publishedVersio