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Acoustic micronektonic distribution and density is structured by macroscale oceanographic processes across 17–48° N latitudes in the North Atlantic Ocean
Get PDFThis study investigates the large-scale distribution patterns of the acoustic scattering layers and micronekton density across the Northeast Atlantic Ocean during daylight hours. A research cruise on board R/V “Kronprins Haakon” was conducted during May 2019 from Cape Verde to Bay of Biscay. Hydrological data were obtained at 20 conductivity-temperature-depth sensor (CTD) stations. To estimate the micronekton densities in front of the trawl, an autonomous echo sounder (120 or 200 kHz) on the headrope of the macroplankton trawl was used. Acoustic data were also collected along the cruise track using ship-mounted multi-frequency echo sounders (backscatter at 18 and 38 kHz was analyzed). Acoustic observations (both at 18, 38 and 120/200 kHz) showed clear patterns in the horizontal distribution of the micronekton during daytime with higher backscatter and echo densities in the south of the study area (from 17 to 37° N), and the absence of high backscatter in the surface from 37 to 45° N. Backscatter and echo densities were found to be significantly influenced by: temperature, salinity, and oxygen, as well as depth and time of the day.publishedVersio
Aquaculture-driven evolution of the salmon louse mtDNA genome
Get PDFResistance toward the antiparasitic pyrethroid, deltamethrin, is reported in the Atlantic salmon louse (Lepeophtheirus salmonis salmonis), a persistent ectoparasite of farmed and wild salmonids. The resistance mechanism is linked to mitochondrial DNA (mtDNA), where genetic markers for resistance have been identified. Here, we investigated how widespread pyrethroid use in aquaculture may have influenced mtDNA variation in lice, and the dispersion of resistant haplotypes across the North Atlantic, using historical (2000–2002 “pre-resistance”) and contemporary (2014–2017 “post-resistance”) samples. To study this, we sequenced ATPase 6 and cytochrome b, genotyped two genetic markers for deltamethrin resistance, and genotyped microsatellites as “neutral” controls of potential population bottlenecks. Overall, we observed a modest reduction in mtDNA diversity in the period 2000–2017, but no reduction in microsatellite variation was observed. The reduction in mtDNA variation was especially distinct in two of the contemporary samples, fixed for one and two haplotypes, respectively. By contrast, all historical samples consisted of close to one mtDNA haplotype per individual. No population genetic structure was detected among the historical samples for mtDNA nor microsatellites. By contrast, significant population genetic differentiation was observed for mtDNA among some of the contemporary samples. However, the observed population genetic structure was tightly linked with the pattern of deltamethrin resistance, and we therefore conclude that it primarily reflects the transient mosaic of pyrethroid usage in time and space. Two historically undetected mtDNA haplotypes dominated in the contemporary samples, both of which were linked to deltamethrin resistance, demonstrating primarily two origins of deltamethrin resistance in the North Atlantic. Collectively, these data demonstrate that the widespread use of pyrethroids in commercial aquaculture has substantially altered the patterns of mtDNA diversity in lice across the North Atlantic, and that long-distance dispersion of resistance is rapid due to high level of genetic connectivity that is observed in this species.publishedVersio
Statistical modelling of voluntary feed intake in individual Atlantic salmon (Salmo salar L.)
Get PDFPrecision feeding aims to provide the correct amount of feed to farmed animals for optimal growth and performance and to avoid feed waste. However, knowledge underlying the meal-to-meal variability in voluntary feed intake of farmed species is still limited. This study examined the relationship between meals, feed deprivation time and the feed (pellets) consumed by Atlantic salmon post smolts. The data was collected from individual fish handfed to satiety without social interaction in three independent short-term (6-12 days) experiments. The fixed variables of our model (feed deprivation time (i.e., time between meals), number of pellets provided, day, previous meal size, and fish growth) explained most of the feed intake (number of pellets ingested) (R2 0.68). Results show that fish ingested more pellets over the course of the trials as they grew, resulting in a positive correlation between feed intake and fish growth (final minus initial fish weight). The time between meals and prior meal size (the number of pellets ingested in the previous meal) significantly affected feed intake in the following meal. Our results suggest that it is possible to optimise meal size by considering the size of the previous meal and the time since it was given.publishedVersio
Havforskningsinstituttets rådgivning for menneskeskapt støy i havet - Kunnskapsgrunnlag, vurderinger og råd for 2023
Get PDFHavforskningsinstituttet gir råd for alle operasjoner til havs som involverer bruk av lydkilder, samt elektromagnetiske kilder som kan påvirke marine økosystemer. Dette inkluderer vitenskapelige undersøkelser, utbygging og sprenging i sjø, seismiske og elektromagnetiske undersøkelser i forbindelse med petroleumsvirksomhet og utbygging og drift av vindkraftanlegg til havs. Denne rapporten er en sammenstilling av tilgjengelig kunnskap omkring hvordan de overnevnte typer av undersjøisk støy påvirker livet i havet. Videre evalueres denne kunnskapen i lys av hvilke konsekvenser dokumenterte effekter kan gi på økosystemet. Denne rapporten er inndelt med et kapittel for hver av de overnevnte støykildene (seismikk, elektromagnetiske undersøkelser, undersjøiske sprenginger og vindkraft til havs), som igjen er inndelt i delkapitler med 1) kunnskapsgrunnlag, 2) konsekvensvurdering og 3) råd. Rapporten inneholder konkrete råd fra Havforskningsinstituttet for 2023 for de ulike typene av støy. I tillegg inneholder rapporten en oversikt over hvor det finnes sårbare koraller i norske farvann. Årsaken til at dette er med er grunnet at mange av operasjonene til havs lager støy også innebærer å plassere ulike måleinstrumenter på bunn, og de bør ikke plasseres i områder med korall-forekomster. Derfor er det relevant å også ha med informasjon om romlig fordeling av koraller her. Rapporten inneholder konkrete råd fra Havforskningsinstituttet for 2023 for de ulike typene av støy og elektromagnetisk stråling. Råd for seismikk og elektromagnetiske undersøkelser gis i form av rådgivningskart, som viser perioder og områder som bør unngås. Disse kartene inngår også i Oljedirektoratets meldesystem.Havforskningsinstituttets rådgivning for menneskeskapt støy i havet - Kunnskapsgrunnlag, vurderinger og råd for 2023publishedVersio
Norwegian kelp forest restauration - Kelp restoration actions in Norway, 1988-2022.
No full textThe extensive kelp forests between 58 and 71oN along the Norwegian coastline have suffered greatly from sea urchin grazing since the 1970-ies (Mid and North Norway) and from turf/filamentous algal competition (South and Vest) the last 20 years. The first restoration effort was hammering sea urchins around a small island in 1988, giving the opportunity for a dense kelp recovery already in 1989. Despite this promising result and many proposals, successful sea urchin removal actions were not initiated until about 2005: two experiments with artificial reefs, three experiments with quicklime, one experiment with exclusion in cages, and some transplants of adult kelps. By the same time some very small efforts were tried in the turfing areas; transplants of juvenile and adult kelps, scraping of turf and sediments. Many methods seemed to be promising, but as long as the environmental conditions favored sea urchins and turf in their respective areas, the restored kelps were of limited duration. One exception is the large scale (70 hectare) quicklime experiment initiating a large-scale and lasting kelp recovery and with further expansion due to sea urchin predation by crabs. This is in accordance with an even more large-scale natural kelp recovery initiated by increasing crab populations reducing sea urchins. A starting Norwegian restoration effort is initiated by commercial harvest of sea urchins by newly developed methods (mainly baited traps) accompanied by voluntary groups (kelp watchers, ecotourism). There, new kelp beds are now appearing (2022). Continuous removing of sea urchins will compensate for the (so far) lack of sea urchin predators in this area.acceptedVersio
Potential role of seaweeds in climate change mitigation
Get PDFSeaweed (macroalgae) has attracted attention globally given its potential for climate change mitigation. A topical and contentious question is: Can seaweeds' contribution to climate change mitigation be enhanced at globally meaningful scales? Here, we provide an overview of the pressing research needs surrounding the potential role of seaweed in climate change mitigation and current scientific consensus via eight key research challenges. There are four categories where seaweed has been suggested to be used for climate change mitigation: 1) protecting and restoring wild seaweed forests with potential climate change mitigation co-benefits; 2) expanding sustainable nearshore seaweed aquaculture with potential climate change mitigation co-benefits; 3) offsetting industrial CO2 emissions using seaweed products for emission abatement; and 4) sinking seaweed into the deep sea to sequester CO2. Uncertainties remain about quantification of the net impact of carbon export from seaweed restoration and seaweed farming sites on atmospheric CO2. Evidence suggests that nearshore seaweed farming contributes to carbon storage in sediments below farm sites, but how scalable is this process? Products from seaweed aquaculture, such as the livestock methane-reducing seaweed Asparagopsis or low carbon food resources show promise for climate change mitigation, yet the carbon footprint and emission abatement potential remains unquantified for most seaweed products. Similarly, purposely cultivating then sinking seaweed biomass in the open ocean raises ecological concerns and the climate change mitigation potential of this concept is poorly constrained. Improving the tracing of seaweed carbon export to ocean sinks is a critical step in seaweed carbon accounting. Despite carbon accounting uncertainties, seaweed provides many other ecosystem services that justify conservation and restoration and the uptake of seaweed aquaculture will contribute to the United Nations Sustainable Development Goals. However, we caution that verified seaweed carbon accounting and associated sustainability thresholds are needed before large-scale investment into climate change mitigation from seaweed projects.publishedVersio
Biological Impacts of Marine Heatwaves
Get PDFClimatic extremes are becoming increasingly common against a background trend of global warming. In the oceans, marine heatwaves (MHWs)—discrete periods of anomalously warm water—have intensified and become more frequent over the past century, impacting the integrity of marine ecosystems globally. We review and synthesize current understanding of MHW impacts at the individual, population, and community levels. We then examine how these impacts affect broader ecosystem services and discuss the current state of research on biological impacts of MHWs. Finally, we explore current and emergent approaches to predicting the occurrence andimpacts of future events, along with adaptation and management approaches. With further increases in intensity and frequency projected for coming decades, MHWs are emerging as pervasive stressors to marine ecosystems globally. A deeper mechanistic understanding of their biological impacts is needed to better predict and adapt to increased MHW activity in the Anthropocene.publishedVersio
Genetic study reveals local differentiation persisting in the face of high connectivity and a genomic inversion likely linked with sexual antagonism in a common marine fish
Get PDFSustainable harvest of wild populations requires knowledge of the underlying population structure. The focus of this study is on goldsinny wrasse (Ctenolabrus rupestris), a small marine fish inhabiting coastal waters of the north-eastern Atlantic. This species is caught in large numbers to serve as cleaner fish in salmonid aquaculture. We genotyped 2073 goldsinny wrasse from 43 sites along the Scandinavian coastline with 143 SNPs. Seven of the SNPs were linked and likely reside within a large genomic inversion dominated by one haplotype. The heterokaryotype of the putative inversion displayed sex-specific growth patterns, potentially resolving sexual antagonism for this trait. The unlinked 134 SNPs showed modest isolation-by-distance with samples from the northernmost locations showing highest divergence, whereas sites farther south were much more interconnected. Genetic divergence (FST) was highly variable among sites within regions, suggesting a varying degree of connectivity and local divergence. We conclude that despite a high degree of gene-flow mediated through pelagic dispersal in early life stages, regional and some local population structure remains due to limited adult movement in addition to other unidentified factors. Consequently, the species might be more vulnerable to local disturbances than previously anticipated.publishedVersio
Characterizing coastal cod vocalization using a towed hydrophone array
Get PDFTo better understand spawning vocalizations of Norwegian coastal cod (Gadus morhua), a prototype eight-element coherent hydrophone array was deployed in stationary vertical and towed horizontal modes to monitor cod sounds during an experiment in spring 2019. Depth distribution of cod aggregations was monitored concurrently with an ultrasonic echosounder. Cod vocalizations recorded on the hydrophone array are analysed to provide time–frequency characteristics, and source level distribution after correcting for one-way transmission losses from cod locations to the hydrophone array. The recorded cod vocalization frequencies range from ∼20 to 600 Hz with a peak power frequency of ∼60 Hz, average duration of 300 ms, and mean source level of 163.5 ± 7.9 dB re 1 μPa at 1 m. Spatial dependence of received cod vocalization rates is estimated using hydrophone array measurements as the array is towed horizontally from deeper surrounding waters to shallow water inlet areas of the experimental site. The bathymetric-dependent probability of detection regions for cod vocalizations are quantified and are found to be significantly reduced in shallow-water areas of the inlet. We show that the towable hydrophone array deployed from a moving vessel is invaluable because it can survey cod vocalization activity at multiple locations, providing continuous spatial coverage that is complementary to fixed sensor systems that provide continuous temporal coverage at a given location.publishedVersio
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