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Elevated sea temperature combined with dietary methionine levels affect feed intake and appetite-related neuropeptide expression in the brains of juvenile cobia (Rachycentron canadum)
Get PDFThis study aimed to determine the impact of elevated temperature combined with different levels of dietary methionine concentrations on feed intake (FI) and brain expression of selected neuropeptides and one receptor involved in appetite control in juvenile cobia (approximately 3.7 g body weight). The genes studies were neuropeptide y, npy; agouti-related protein, agrp; cocaine- and amphetamine-regulated transcript, cart; cholecystokinin, cck and melanocortin 4 receptor; mc4r. The cobia were reared at typical sea water temperature in Vietnam (30 °C) and elevated temperature (34°C; selected as one of the predicted scenarios of climate change). The fish were fed diets with different levels of methionine: deficient (M9; 9.1 g/kg), sufficient (M12; 12.8 g/kg) and surplus (M16, 16.8 g/kg) for 6 weeks (triplicate tanks per treatment). Both dietary methionine concentration and temperature affected FI in cobia. Dietary methionine deficiency (i.e., M9) and elevated temperature reduced FI in cobia. Temperature significantly influenced the mRNA expression of agrp, cart, cck and mc4r. Expression of the orexigenic neuropeptide npy was consistently higher before the meal than after the meal for all diets and at both temperatures. At 30°C, prefeeding levels of npy correlated with both increased methionine levels and FI. The interaction between dietary methionine and temperature on the levels of brain npy expression was significant (P<0.05). There was higher brain expression of agrp, cart and cck in cobia at 34°C than in fish at 30°C, which was correlated with a lower FI. In conclusion, both feeding, temperature and/or dietary methionine levels affected the brain expression of npy and agrp, cart, cck and mc4r. This suggests that these neuropeptides as well as the mc4r receptor are actively involved in adjusting feed intake to compensate for changing energetic demands, as well as metabolic adjustments due to the variable availability of methionine at elevated temperature.publishedVersio
trec: An R package for trend estimation and classification to support integrated ecosystem assessment of the marine ecosystem and environmental factors
Get PDFSolvang and Planque [ICES Journal of Marine Science, 77, pp.2529–2540, (2020)] provided a trend estimation and classification (TREC) approach to estimating dominant common trends among multivariate time series observations. This approach was developed to improve communication among stakeholders like marine managers, industry representatives, non-governmental organizations, and governmental agencies as they investigate the common tendencies between a biological community in a marine ecosystem and the local environmental factors. The tasks of trend estimation and classification in the original computational procedure have been revised, and new features include an automatic icon assignment algorithm using a multinomial logistic discriminator. In this paper, we present R package trec. Implementation of this package involves three partitions corresponding to TREC1) estimating trends from observed time series data; TREC2) classifying two/three rough patterns; and TREC3) generating a table summarizing categories of common configurations (trends) and the automatic icon assignments to them. The proposed trec focuses on investigating mean non-stationary long-term trends of data, and it works for any length of time steps. It is not necessary to apply a stationary Gaussian assumption to the estimated trends to investigate the common trends, which are interpreted as common variations of biological and environmental data.publishedVersio
Mussel farming production capacity and food web interactions in a mesotrophic environment
Get PDFLow trophic aquaculture (LTA), such as bivalve farming, offers promising avenues to supply sustainable seafood and aquafeed. While bivalve farming usually occurs in highly productive coastal areas which already support numerous human activities and suffer from environmental pressures, numerical tools offer a promising avenue to explore and assess biomass production potential and associated ecosystemic impacts for further development of the industry and prospection of new exploitation sites. In this study, we coupled an ecophysiological model, the dynamic energy budget theory (DEB), with an ecosystem model (NORWECOM.E2E) to simulate blue mussel Mytilus spp. farming production and effects based on the food web in the mesotrophic Hardangerfjord in western Norway. We tested several levels of fjord-scale farming intensity and assessed 2 production purposes: aquafeed and human consumption. Results suggested the Hardangerfjord could host large-scale mussel farming for both purposes. However, large exploitation schemes displayed detrimental effects on individual mussel growth (39% less wet mass after 2 yr) and especially on secondary production (decrease of 33% after 1 yr) due to acute trophic competition. Simulations showed short production cycles for aquafeed were more efficient to exploit primary production, since young and small mussels have lower maintenance and reproduction costs. Dissolved nutrient inputs from salmonid farms had marginal effects on primary production (<2%). However, salmonid and mussel farming activities could compete for the sites with the highest production potential.publishedVersio
Deep Semi-Supervised Semantic Segmentation in Multi-Frequency Echosounder Data
Get PDFMulti-frequency echosounder data can provide a broad understanding of the underwater environment in a non-invasive manner. The analysis of echosounder data is, hence, a topic of great importance for the marine ecosystem. Semantic segmentation, a deep learning based analysis method predicting the class attribute of each acoustic intensity, has recently been in the spotlight of the fisheries and aquatic industry since its result can be used to estimate the abundance of the marine organisms. However, a fundamental problem with current methods is the massive reliance on the availability of large amounts of annotated training data, which can only be acquired through expensive handcrafted annotation processes, making such approaches unrealistic in practice. As a solution to this challenge, we propose a novel approach, where we leverage a small amount of annotated data (supervised deep learning) and a large amount of readily available unannotated data (unsupervised learning), yielding a new data-efficient and accurate semi-supervised semantic segmentation method, all embodied into a single end-to-end trainable convolutional neural networks architecture. Our method is evaluated on representative data from a sandeel survey in the North Sea conducted by the Norwegian Institute of Marine Research. The rigorous experiments validate that our method achieves comparable results utilizing only 40 percent of the annotated data on which the supervised method is trained, by leveraging unannotated data. The code is available at https://github.com/SFI-Visual-Intelligence/PredKlus-semisup-segmentation.Deep Semi-Supervised Semantic Segmentation in Multi-Frequency Echosounder DatasubmittedVersionsubmittedVersionsubmittedVersio
Toktrapport fra økosystemtokt i Vestlandsfjordene — Hydrografi, vannkjemi, reker, krill, bunnfisk, tobis og perifylla
Get PDFDen Strategiske instituttsatsingen CoastRisk (2019–2023) har hatt som mål å styrke kunnskapsgrunnlaget om ulike påvirkningsfaktorers betydning for kystøkosystemenes tilstand, funksjon og utvikling. Vestland fylke er ett av flere studieområder i prosjektet, med bla. dypvannsreke (Pandalus borealis), kysttorsk (Gadus morhua), tobis og dyreplankton valgt ut som fokusarter/-grupper.Toktrapport fra økosystemtokt i Vestlandsfjordene — Hydrografi, vannkjemi, reker, krill, bunnfisk, tobis og perifyllapublishedVersio
Effects of local density dependence and temperature on the spatial synchrony of marine fish populations
Get PDFDisentangling empirically the many processes affecting spatial population synchrony is a challenge in population ecology. Two processes that could have major effects on the spatial synchrony of wild population dynamics are density dependence and variation in environmental conditions like temperature. Understanding these effects is crucial for predicting the effects of climate change on local and regional population dynamics. We quantified the direct contribution of local temperature and density dependence to spatial synchrony in the population dynamics of nine fish species inhabiting the Barents Sea. First, we estimated the degree to which the annual spatial autocorrelations in density are influenced by temperature. Second, we estimated and mapped the local effects of temperature and strength of density dependence on annual changes in density. Finally, we measured the relative effects of temperature and density dependence on the spatial synchrony in changes in density. Temperature influenced the annual spatial autocorrelation in density more in species with greater affinities to the benthos and to warmer waters. Temperature correlated positively with changes in density in the eastern Barents Sea for most species. Temperature had a weak synchronizing effect on density dynamics, while increasing strength of density dependence consistently desynchronised the dynamics. Quantifying the relative effects of different processes affecting population synchrony is important to better predict how population dynamics might change when environmental conditions change. Here, high degrees of spatial synchrony in the population dynamics remained unexplained by local temperature and density dependence, confirming the presence of additional synchronizing drivers, such as trophic interactions or harvesting.publishedVersio
Utvikling av et miljø- og ressursvennlig teinefiske etter snøkrabbe - Økt fangsteffektivitet, selektivitet og velferd
Get PDFProsjektet «Utvikling av et miljø- og ressursvennlig teinefiske etter snøkrabbe» har bestått av fire arbeidspakker og ble gjennomført som en kombinasjon av atferdsforsøk i lab og fiskeforsøk i felt. I den første arbeidspakken «Økt fangsteffektivitet for krabber over minstemål» ble det vist at små masker i teinene øker fangst av alle størrelsesgrupper. I den andre arbeidspakken «Effektiv utsortering av undermålskrabber på fiskedypet» ble det vist at spalter effektivt sorterer ut undermålskrabbe, men det tapes også overmålskrabbe. Spaltene kan også lett tilstoppes av overmålskrabbe. Teinene selekterer mye ut gjennom bunnen på vei til overflaten og her er det potensiale til å sortere ut enda mer med alternativ bunnutforming. Plastkrager for å hindre undermålskrabbe i å nå inngangen på toppen av teinene fungerte ikke. Krabben fikk lett tak i uregelmessigheter i kragen og klatret over hinderet. I den tredje arbeidspakken «Rømmingsåpninger i tapte teiner» ble det testet ulike tykkelser av bomullstråd i kommersielt fiskeri. Bomullstråd er foreløpig den enkleste måten å forhindre spøkelsesfiske når teiner går tapt. Det ble også gjort forsøk på standardisering av bomullstråd gjennom flere strekkcelletester, ulike metoder for måling av diameter samt ved å tilføye Rtex (vekt per 1000 meter) for beskrivelse av tråd. I den fjerde arbeidspakken «Undervannsbøye med akustisk utløser (IceCatcher)» ble det gjort flere vellykkede funksjonstester om bord på forskningsfartøy, mens det fortsatt mangler tester i fiskeri under kommersiell fangst og reelle isforhold. Prosjektet har gitt et betydelig bidrag til vår forståelse av effektivitet og seleksjon i snøkrabbeteiner. En viktig konklusjon fra studiene er at utformingen teinene har i dag er den hittil beste balansen mellom effektivitet og seleksjon. Det bør imidlertid gjennomføres fiskeforsøk med ulike maskestørrelser for å ytterligere redusere fangst av undermålskrabbe som vil bli enda viktigere med en forespeilet kvotetildeling og høyre pris for den største krabben. Arbeidet med nedbrytbar tråd har blitt brukt i rådgivningen fra HI og grunnlag for et nært forestående påbud i snøkrabbefisket. Konseptutviklingen av IceCatcher viser at det er fullt mulig å lage systemer som kan forhindre tap av redskap, men at det må rettes betydelig innsats for å komme fram til et ferdigutviklet produkt og kommersialisering.Utvikling av et miljø- og ressursvennlig teinefiske etter snøkrabbe - Økt fangsteffektivitet, selektivitet og velferdpublishedVersio
Movement diversity and partial sympatry of coastal and Northeast Arctic cod ecotypes at high latitudes
Get PDFMovement diversity within species represent an important but often neglected, component of biodiversity that affects ecological and genetic interactions, as well as the productivity of exploited systems. By combining individual tracking data from acoustic telemetry with novel genetic analyses, we describe the movement diversity of two Atlantic cod Gadus morhua ecotypes in two high-latitude fjord systems: the highly migratory Northeast Arctic cod (NEA cod) that supports the largest cod fishery in the world, and the more sedentary Norwegian coastal cod, which is currently in a depleted state. As predicted, coastal cod displayed a higher level of fjord residency than NEA cod. Of the cod tagged during the spawning season, NEA cod left the fjords permanently to a greater extent and earlier compared to coastal cod, which to a greater extent remained resident and left the fjords temporarily. Despite this overall pattern, horizontal movements atypical for the ecotypes were common with some NEA cod remaining within the fjords year-round and some coastal cod displaying a low fjord fidelity. Fjord residency and exit timing also differed with spawning status and body size, with spawning cod and large individuals tagged during the feeding season more prone to leave the fjords and earlier than non-spawning and smaller individuals. While our results confirm a lower fjord dependency for NEA cod, they highlight a movement diversity within each ecotype and sympatric residency between ecotypes, previously undetected by population-level monitoring. This new knowledge is relevant for the management, which should base their fisheries advice for these interacting ecotypes on their habitat use and seasonal movements.publishedVersio
Fluctuating Atlantic inflows modulate Arctic atlantification
Get PDFEnhanced warm, salty subarctic inflows drive high-latitude atlantification, which weakens oceanic stratification, amplifies heat fluxes, and reduces sea ice. In this work, we show that the atmospheric Arctic Dipole (AD) associated with anticyclonic winds over North America and cyclonic winds over Eurasia modulates inflows from the North Atlantic across the Nordic Seas. The alternating AD phases create a “switchgear mechanism.” From 2007 to 2021, this switchgear mechanism weakened northward inflows and enhanced sea-ice export across Fram Strait and increased inflows throughout the Barents Sea. By favoring stronger Arctic Ocean circulation, transferring freshwater into the Amerasian Basin, boosting stratification, and lowering oceanic heat fluxes there after 2007, AD+ contributed to slowing sea-ice loss. A transition to an AD− phase may accelerate the Arctic sea-ice decline, which would further change the Arctic climate system.acceptedVersio
Spatial structuring in early life stage fish diversity in the Scotia Sea region of the Southern Ocean
Get PDFThe fish community of the Scotia Sea is diverse and plays key roles in Antarctic food webs and biogeochemical cycling. However, knowledge of the spatial and community structure of their early life stages is limited, particularly in the region surrounding the South Orkney Islands. Here we examine the structure of the early life stage fish community in the epipelagic using data from a basin-scale survey conducted in early 2019, which sampled the top 200 m of the water column. 347 early life stage fish from 19 genera were caught in 58 hauls. A third of all specimens belonged to the genus Notolepis and the nine most common genera comprised over 90% of specimens. Cluster analysis revealed five distinct groupings, the most common were a group dominated by pelagic and shelf slope genera (Notolepis, Muraenolepis and Electrona) found mainly in oceanic waters (depth ≥ 1000 m), and a group dominated by species with demersal or benthopelagic adults (Chionodraco, Chaenocephalus and Nototheniops) found mainly in shelf waters. Bottom depth was the main environmental determinant of community structure, separating the diverse on-shelf assemblage at the South Orkneys from the less species-rich community of widespread oceanic taxa. Our results indicate the highest diversities of early life stages of endemic fish occur on the shelf and near-shelf areas. Dedicated monitoring is recommended to understand the seasonal differences in larval community assemblages and the implications of early life stages fish bycatch within the krill fishery.publishedVersio