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Marine typology - Investigation of marine water types in context of Vannforskriften
No full textInndeling av kystvann i vanntyper er fundamentet for fastsetting av vannkvalitet i henhold til Vannforskriften (2006, Vannrammedirektivet). Vanntyper er karakterisert ved fysiske og kjemiske faktorer og geografisk avgrenset på et sjøkart ut til 1 nautisk mil utenfor grunnlinjen. Vannkvalitet fastsettes basert på økologisk tilstand til planteplankton, makroalger, ålegress og bunndyr, målt som avvik fra vanntypens referansetilstand. Erfaring har vist at det er utfordringer og feil i dagens inndeling i vanntyper og Miljødirektoratet ønsket en helhetlig revisjon av vanntyper i kystvann. Havforskningsinstituttet fikk i oppdrag å utrede og foreslå en ny inndeling av kystvannet i vanntyper. Det var en målsetning å bygge inndelingen på modellerte fysiske og kjemiske vannparametere, og det har i arbeidets gang vært mange møter med vannmyndigheter for å komme fram til gode løsninger. Det har derfor vært viktig å dokumentere fremgangsmåte, vurderinger og valg som er gjort i arbeidets gang, fram til foreliggende forslag til 35 vanntyper fordelt på 6 økoregioner. Arbeidet med å tegne inn vanntyper geografisk i ArcGIS (versjon 10) ble avsluttet i desember 2022 og kvalitetssikrede kartfiler (shapefiler) ble levert til Miljødirektoratet mars 2023.Marin typologi — Utredning av marine vanntyper i vannforskriftsammenhengMarine typology - Investigation of marine water types in context of VannforskriftenpublishedVersio
Diet and trophic structure of fishes in the Barents Sea: Effects of size within (ontogenetic) and between species
Full text linkA large data set on stomach content (over 27,000 individual fish) – collected in the Barents Sea in 2015 – was used to examine ontogenetic and interspecific changes in diet with size for 35 fish species. The analysis combined the use of hierarchical clustering and random forest. Two different diet metrics were used (% weight of prey types per weight of stomach content or per weight of fish, the latter reflecting also feeding intensity), and data were analysed based on average diet of predator groups (species and size groups) across the entire sample series (from the whole Barents Sea in different seasons), or for data broken down by geographical areas and seasons. Similar trophic groups (clusters) were identified for the various data sets suggesting that the results on trophic structure were robust. The trophic groups including size information were broadly similar to groups found earlier with data averaged at species level. Hierarchical clustering produces a hierarchy of trophic groups (or trophic guilds) at various levels of diet dissimilarity. With 12 clusters identified, one cluster had fish as dominant prey, and 5–6 others had either plankton or benthos as dominant prey. The clusters tended to be distinct and homogenous with one dominant prey category in average diet (often > 60 %). This was especially the case for the plankton clusters, with copepods, euphausiids, hyperiid amphipods, or gelatinous zooplankton as dominant prey in each of 4 trophic groups. The benthos clusters tended to be less dissimilar with more overlap in diet composition, with predominance of either hard-shelled forms (echinoderms and molluscs) or softer prey (polychaetes and crustaceans) for groups of clusters. There were clear patterns of ontogenetic shifts in fish diet. Fish that clustered as piscivores at larger size tended to grow from being planktivores when smaller. Smaller species of planktivores or benthivores shifted position among trophic groups but remained within the categories of planktivores or benthivores, respectively. Taxonomy (species) tended to be more important than size for explaining the diet composition of the different clusters of fish predators.publishedVersio
Efficacy of lime, hydrogen peroxide and azamethiphos as potential control treatments against the proliferation of the invasive ascidian Didemnum vexillum
Full text linkThe invasion of the colonial ascidian Didemnum vexillum (Kott, 2002) represents a significant threat to marine ecosystems. In Norway, D. vexillum was recorded for the first time in 2020 and has since continued spreading along the coast. Although the total eradication of this species appears highly unlikely, the implementation of control measures is important to slow down its proliferation and limit the impacts on important species and habitats. In this study, we performed three laboratory experiments, to separately test the effects of lime (fine and coarse quicklime particles and hydrated lime), hydrogen peroxide (H2O2; 0, 1000, 2000 and 4000 mg l-1) and Azamethiphos (0, 50, 100 and 200 µg l-1 ), on the biofouling cover of D. vexillum. No significant effect of Azamethiphos was detected on D. vexillum cover after 1 hr of exposure, while exposure to H2O2 for 1 hr only reduced its biofouling cover by 50% after exposure to the highest concentration (4000 mg l-1 ). Conversely, both fine and coarse quicklime particles appeared as suitable control options, reducing the size of the colonies by 100% and 99%, respectively, after exposure for 20 hrs. Additionally, treatment with hydrated lime induced a significant decline in D. vexillum cover by about 89% after 1 hr of exposure. Our results suggest the importance of considering the seasonal variations in environmental conditions and the biology of D. vexillum, to optimize the efficacy of the treatment. Here, we suggest using quicklime and hydrated lime between October and December in the Northern Hemisphere, to benefit from the natural degeneration of D. vexillum during winter and to more effectively eradicate potential remnants that could serve as a basis for regeneration.publishedVersio
Comparison of WP-2 and MOCNESS plankton samplers for measuring zooplankton biomass in the Barents Sea ecosystem
Full text linkZooplankton in the Barents Sea has been monitored on an annual autumn survey since the late 1980s, using vertical WP-2 and oblique Multiple Opening and Closing Net and Environmental Sensing System (MOCNESS) tows over the water column. Sampling with MOCNESS is used to describe the vertical distribution and more frequent sampling with WP-2 (~3:1) to describe the horizontal distribution. We use here a large cumulative data set of 874 MOCNESS and 2850 WP-2 stations with data on size-fractioned dry-weight biomass to compare the two zooplankton sampling gears. MOCNESS is consistently collecting more biomass of the large size fraction (>2 mm screen size) by ~20% and less of the small fraction (<1 mm) by ~30% compared to WP-2. This is interpreted to reflect more extrusion of small plankton and less avoidance by larger plankton with the MOCNESS. The data set has been collected by three research vessels. There was a difference in vertical speed in oblique tows of MOCNESS among the ships but no clear effect on volume filtered per unit time. This demonstrates operational consistency and suggests the use of a constant flow factor (distance per flowmeter count) when calculating results over the time series. The issue of calibration of traditional flowmeters on oblique tows needs further examination.publishedVersio
Self-supervised feature learning for acoustic data analysis
Full text linkAcoustic surveys play a pivotal role in fisheries management. During the surveys, acoustic signals are sent into the water and the strength of the reflection, so-called backscatter, is recorded. The collected data are typically annotated manually, a process that is both labor-intensive and time-consuming, to support acoustic target classification (ATC). The primary objective of this study is to develop an annotation-free deep learning model that extracts acoustic features and improves the representation of acoustic data. For this purpose, we adopt a self-supervised method inspired by the Self DIstillation with NO Labels (DINO) model. Extracting useful acoustic features is an intricate task due to the inherent variability and complexity in biological targets, as well as environmental and technical factors influencing sound interactions. The proposed model is trained with three sampling methods: random sampling, which ignores class imbalance present in the acoustic survey data; class-balanced sampling, which ensures equal representation of known categories; and intensity-based sampling, which selects data to capture backscatter variations. The quality of extracted features is then evaluated and compared. We show that the extracted features lead to improvement, in comparison to using the untreated data, in the discriminative power of several machine learning methods (k-nearest neighbor (kNN), linear regression, multinomial logistic regression) for ATC. The improvement was measured through higher accuracy in kNN (77.55% vs. 71.93%), Macro AUC in logistic regression (0.92 vs. 0.80), and R^2 in linear regression (0.69 vs. 0.45) when comparing extracted features to the untreated data. Our findings highlight the advantage of applying emerging self-supervised techniques in fisheries acoustics. This study thus contributes to the ongoing efforts to improve the efficiency of acoustic surveys in fisheries management.Self-supervised feature learning for acoustic data analysispublishedVersio
Effect of environmental drivers on the spatiotemporal distribution of mackerel at age in the Nordic Seas during 2010−20
Full text linkA joint spatio–temporal distribution model of mackerel (ages 3–10) was developed to investigate the age-based responses of mackerel to three environmental drivers: sea surface temperature (SST), mixed layer depth, and chlorophyll-a concentration during the summer months 2010–20 in the Nordic Seas. The study showed that SST was the most important variable amongst the ones tested and had the strongest impact on the distribution of the younger age classes (3–5), which had a narrower range of favourable SST and a stronger aversion to cold temperatures than older individuals. Consequently, the impact of SST differed regionally; in the polar front regions, SST explained up to 61% of the variability in the observed density of young individuals, where Arctic water masses likely acted as a barrier to these young individuals. That said, part of it could be confounded with the limited migration capability of young mackerels, which could not reach the furthest frontal regions. In warmer southern waters, the same environmental variables had less explanatory power for mackerel of all ages. Individuals in the south were likely not constrained by temperature and perhaps more influenced by other variables, such as food availability or ocean current (throughout their migration path), for which appropriate data are lacking. Moreover, the model showed that older mackerel were distributed more to the north and west, and their migration pattern changed when the 2013 year-class no longer migrated to the west compared to previous year-classes. Additionally, all-year classes started migrating more eastward from summer 2018.publishedVersio
Multidrug-resistant Enterococcus faecium strains enter the Norwegian marine environment through treated sewage
Full text linkThis study aimed to understand the antibiotic resistance prevalence among Enterococcus spp. from raw and treated sewage in Bergen city, Norway. In total, 517 Enterococcus spp. isolates were obtained from raw and treated sewage from five sewage treatment plants (STPs) over three sampling occasions, with Enterococcus faecium as the most prevalent (n = 492) species. E. faecium strains (n = 307) obtained from the influent samples, showed the highest resistance against quinupristin/dalfopristin (67.8%). We observed reduced susceptibility to erythromycin (30.6%) and tetracycline (6.2%) in these strains. E. faecium strains (n = 185) obtained from the effluent samples showed highest resistance against quinupristin/dalfopristin (68.1%) and reduced susceptibility to erythromycin (24.9%) and tetracycline (8.6%). We did not detect resistance against last-resort antibiotics, such as linezolid, vancomycin, and tigecycline in any of the strains. Multidrug-resistant (MDR) E. faecium strains were detected in both influent (2.3%) and effluent (2.2%) samples. Whole genome sequencing of the Enterococcus spp. strains (n = 25) showed the presence of several antibiotic resistance genes, conferring resistance against aminoglycosides, tetracyclines, and macrolides, as well as several virulence genes and plasmid replicons. Two sequenced MDR strains from the effluents belonged to the hospital-associated clonal complex 17 and carried multiple virulence genes. Our study demonstrates that clinically relevant MDR Enterococcus spp. strains are entering the marine environment through treated sewage.publishedVersio
Flagged observation analyses as a tool for scoping and communication in integrated ecosystem assessments
Full text linkArticle Authors Metrics Comments Media Coverage Peer Review Abstract Introduction Statistical method Illustrative examples Discussion Supporting information Acknowledgments References Reader Comments Figures Abstract Working groups for integrated ecosystem assessments are often challenged with understanding and assessing recent change in ecosystems. As a basis for this, the groups typically have at their disposal many time series and will often need to prioritize which ones to follow up for closer analyses and assessment. In this article we provide a procedure termed Flagged Observation analysis that can be applied to all the available time series to help identifying time series that should be prioritized. The statistical procedure first applies a structural time series model including a stochastic trend model to the data to estimate the long-term trend. The model adopts a state space representation, and the trend component is estimated by a Kalman filter algorithm. The algorithm obtains one- or more-years-ahead prediction values using all past information from the data. Thus, depending on the number of years the investigator wants to consider as “the most recent”, the expected trend for these years is estimated through the statistical procedure by using only information from the years prior to them. Forecast bands are estimated around the predicted trends for the recent years, and in the final step, an assessment is made on the extent to which observations from the most recent years fall outside these forecast bands. Those that do, may be identified as flagged observations. A procedure is also presented for assessing whether the combined information from all the most recent observations form a pattern that deviates from the predicted trend and thus represents an unexpected tendency that may be flagged. In addition to form the basis for identifying time series that should be prioritized in an integrated ecosystem assessment, flagged observations can provide the basis for communicating with managers and stakeholders about recent ecosystem change. Applications of the framework are illustrated with two worked examples.publishedVersio
How Fish Population Genomics Can Promote Sustainable Fisheries: A Road Map
Full text linkMaintenance of genetic diversity in marine fishes targeted by commercial fishing is a grand challenge for the future. Most of these species are abundant and therefore important for marine ecosystems and food security. Here, we present a road map of how population genomics can promote sustainable fisheries. In these species, the development of reference genomes and whole genome sequencing is key, because genetic differentiation at neutral loci is usually low due to large population sizes and gene flow. First, baseline allele frequencies representing genetically differentiated populations within species must be established. These can then be used to accurately determine the composition of mixed samples, forming the basis for population demographic analysis to inform sustainably set fish quotas. SNP-chip analysis is a cost-effective method for determining baseline allele frequencies and for population identification in mixed samples. Finally, we describe how genetic marker analysis can transform stock identification and management.publishedVersio
Sjøpattedyrutvalget 2024 - Tilrådning om forskning og forvaltning
Full text linkSjøpattedyrutvalget hadde sitt årlige møte i Tromsø 18.-19. november 2024. Utvalgets oppgave er å utarbeide anbefalinger og tilrådninger om forskning og forvaltning av sjøpattedyr i Norge. Dette inkluderer kvoteråd for arter som fangstes eller jaktes. I denne rapporten oppsummeres sakene som ble behandlet på årets møte.Sjøpattedyrutvalget 2024 - Tilrådning om forskning og forvaltningpublishedVersio