Variability in Calanus spp. abundance on fine- to mesoscales in an Arctic fjord : implications for little auk feeding

Paid Open Acces

Detachment and re-attachment of Salmon lice during full-scale delousing operations on Salmon farms

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Light in the dark – the role of irradiance in the high Arctic marine ecosystem during polar night

In this thesis, I studied the role of light in the Arctic marine ecosystem during the polar night; a time of year when it appears completely dark to the human eye. I have studied patterns of diel vertical migration (DVM) of zooplankton, and the vision of selected Arctic organisms was investigated by using hyperspectral imaging as well as behavioural experiments. During polar night, patterns of bioluminescence and DVM were mapped in Kongsfjorden, Svalbard, using an autonomous underwater vehicle (AUV) as well as zooplankton net hauls. Bioluminescence was, as the first registration during the polar night, documented throughout the water column. Diel changes in bioluminescence over depth were observed, with a significantly greater proportion of the more intense flashes occurring in surface layers during night and at depth during day. In addition, investigations using acoustic backscatter as well as plankton net hauls supported that the larger zooplankton, like Calanus spp., performed DVM in Kongsfjorden during polar night. To investigate the spectral characteristics of the eyes of different organisms, the eyes of live specimens of different copepod and amphipod species were characterised using a hyperspectral imager. The spectral properties of the eyes were found to match the light climate of their habitats, sympagic and shallow-living pelagic species probably absorbing in blue and some in green wavebands, while deeper-living pelagic and hyperbenthic species absorbed mainly in blue. The sensitivity to ambient wavelengths may be part of the explanation to how organisms can stay active during the polar night, when ambient irradiance is very limited. Calanus spp. is a genus highly important to the Arctic marine ecosystem, and was selected for studies of potential response to extremely low irradiance levels. An experimental setup was developed to investigate their phototactic behaviour (behavioural response to irradiance). For laboratory cultured C. finmarchicus (originating from Trondheimsfjorden), the lowest irradiance levels eliciting a phototactic response were in the range of 1-10×10-6 μmol photons m-2 s-1. Using parameters from spring phytoplankton bloom conditions, when attenuation of light is high, the irradiance threshold levels for C. finmarchicus were estimated to correspond to 48-57 m depth in a fjord (Trondheimsfjorden) and 158-186 m in open ocean (Norwegian Sea), which matched with reported depth ranges of natural C. finmarchicus populations. The phototactic behaviour of Calanus spp. sampled during polar night was investigated, to start revealing the visual capabilities of polar night acclimated organisms. The copepods showed highest sensitivity towards blue and green wavebands, responding to irradiance as low as 0.3-4.0×10-6 μmol photons m-2 s-1, while the corresponding values for red was about three orders of magnitude higher. Correlating the lowest threshold level for response with estimations of polar night irradiance with depth, it was suggested that Calanus spp. may respond to irradiance from the night sky down to approximately 40-50 m, moonlight to 100-140 m, and aurora borealis down to 60-100 m depth. Thus, irradiance may be the proximate cue for the observed DVM patterns, and it was suggested that the background irradiance from the sun, moonlight, as well as aurora affects the pelagic ecosystem during the polar night

Biofouling on salmon pen nets and cleaner fish shelters does not harbor planktonic stages of sea lice

The objective of the current study was to determine the extent to which planktonic sea lice (Lepeophtheirus salmonis Krøyer, 1838 and Caligus elongatus Nordmann, 1832) were present in the biofouling on open-sea net pens used for commercial rearing of Atlantic salmon (Salmo salar L.), and to assess if biofouling organisms on nets act as barriers similar to salmon lice skirts. We have examined two possible interactions of biofouling and planktonic sea lice, the first was if biofouling could function as a microhabitat for planktonic sea lice, with resuspension of sea lice during net cleaning operations. The second interaction was if biofouling may cause a retaining effect on the transport of planktonic stages out of the net pen. These interactions were investigated at different commercial salmon farms. With only one sea louse found among the biofouling on nets and cleaner fish shelters, we found no indication that sea lice utilized biofouling as a reservoir. This was further supported by the lack of impact on the proportion of samples with sea lice and the average density of sea lice in the water following the release of biofouling material during in situ net cleaning. Furthermore, the presence of biofouling had no effect on the proportion of samples with sea lice or the average density of planktonic sea lice in the net pens. The presence of a lice skirt resulted, however, in a significantly higher proportion of samples with planktonic sea lice inside the net pen in one of the two sites utilizing lice skirts. The results of our study suggested that the presence of biofouling has no influence on the average density and proportion of samples with planktonic stages of sea lice and that planktonic sea lice do not inhabit biofouling.publishedVersio

Principles and Methods of Counteracting Harmful Salmon–Arthropod Interactions in Salmon Farming: Addressing Possibilities, Limitations, and Future Options

The arthropod salmon louse (Lepeophtheirus salmonis) is a major threat to Atlantic salmon aquaculture and wild salmonids. Essentially like in monoculture, very high concentrations of susceptible hosts may result in high reproduction and severe production of waves of pests. Pest management is crucial both for fish health and protection of wild fish populations from aquaculture influence. Various methods have been utilized to control salmon lice infestations, such as pesticide use, physical treatments, construction modifications, fallowing, breeding, vaccination, and biological control. Most of the methods are partially successful, but none completely fulfills the necessary pest control strategy. Like in agriculture, lice/pest management is an arms race, but the marine environment makes it even more difficult to precisely hit the target pest and avoid unintended negative effects on general wildlife. In this study, we provide an overview of the methods and principles of salmon lice management and address current possibilities and limitations. We also highlight the potential of emerging strategies and enabling technologies, like genome editing, RNA interference, and machine learning, in arthropod management in aquaculture

Phenylalanine Hydroxylase RNAi Knockdown Negatively Affects Larval Development, Molting and Swimming Performance of Salmon Lice

Phenylalanine hydroxylase (PAH) is a crucial enzyme involved in tyrosine biosynthesis, having roles in neurological and physiological processes. The purpose of PAH has received little attention in crustaceans despite extensive investigations in other arthropods. Here, we characterize the PAH gene for the first time in the parasite Lepeophtheirus salmonis, a copepod that is responsible for huge economic losses in salmonid fish farming. Phylogenetic and sequence analyses confirmed that LsPAH is closely related to the metazoan PAH with conserved ACT regulatory and catalytic domains. Temporal expression patterns revealed that LsPAH is expressed throughout all developmental stages peaking during the copepodite stages, suggesting an essential role in developmental physiology. We used RNAi to knockdown LsPAH expression in the nauplius I stage to study developmental function during the larval stages. PAH knockdown impaired larval development, molting and swimming ability with severe morphological defects. This study provides insight into the role of PAH in copepods and demonstrates the importance of this metabolic gene in salmon louse growth and development

Biofouling on salmon pen nets and cleaner fish shelters does not harbor planktonic stages of sea lice

The objective of the current study was to determine the extent to which planktonic sea lice (Lepeophtheirus salmonis Krøyer, 1838 and Caligus elongatus Nordmann, 1832) were present in the biofouling on open-sea net pens used for commercial rearing of Atlantic salmon (Salmo salar L.), and to assess if biofouling organisms on nets act as barriers similar to salmon lice skirts. We have examined two possible interactions of biofouling and planktonic sea lice, the first was if biofouling could function as a microhabitat for planktonic sea lice, with resuspension of sea lice during net cleaning operations. The second interaction was if biofouling may cause a retaining effect on the transport of planktonic stages out of the net pen. These interactions were investigated at different commercial salmon farms. With only one sea louse found among the biofouling on nets and cleaner fish shelters, we found no indication that sea lice utilized biofouling as a reservoir. This was further supported by the lack of impact on the proportion of samples with sea lice and the average density of sea lice in the water following the release of biofouling material during in situ net cleaning. Furthermore, the presence of biofouling had no effect on the proportion of samples with sea lice or the average density of planktonic sea lice in the net pens. The presence of a lice skirt resulted, however, in a significantly higher proportion of samples with planktonic sea lice inside the net pen in one of the two sites utilizing lice skirts. The results of our study suggested that the presence of biofouling has no influence on the average density and proportion of samples with planktonic stages of sea lice and that planktonic sea lice do not inhabit biofouling

Biofouling on salmon pen nets and cleaner fish shelters does not harbor planktonic stages of sea lice

The objective of the current study was to determine the extent to which planktonic sea lice (Lepeophtheirus salmonis Krøyer, 1838 and Caligus elongatus Nordmann, 1832) were present in the biofouling on open-sea net pens used for commercial rearing of Atlantic salmon (Salmo salar L.), and to assess if biofouling organisms on nets act as barriers similar to salmon lice skirts. We have examined two possible interactions of biofouling and planktonic sea lice, the first was if biofouling could function as a microhabitat for planktonic sea lice, with resuspension of sea lice during net cleaning operations. The second interaction was if biofouling may cause a retaining effect on the transport of planktonic stages out of the net pen. These interactions were investigated at different commercial salmon farms. With only one sea louse found among the biofouling on nets and cleaner fish shelters, we found no indication that sea lice utilized biofouling as a reservoir. This was further supported by the lack of impact on the proportion of samples with sea lice and the average density of sea lice in the water following the release of biofouling material during in situ net cleaning. Furthermore, the presence of biofouling had no effect on the proportion of samples with sea lice or the average density of planktonic sea lice in the net pens. The presence of a lice skirt resulted, however, in a significantly higher proportion of samples with planktonic sea lice inside the net pen in one of the two sites utilizing lice skirts. The results of our study suggested that the presence of biofouling has no influence on the average density and proportion of samples with planktonic stages of sea lice and that planktonic sea lice do not inhabit biofouling

Data from: Inferences of genetic architecture of bill morphology in house sparrow using a high density SNP array point to a polygenic basis

Understanding the genetic architecture of quantitative traits can provide insights into the mechanisms driving phenotypic evolution. Bill morphology is an ecologically important and phenotypically variable trait, which is highly heritable and closely linked to individual fitness. Thus, bill morphology traits are suitable candidates for gene mapping analyses. Previous studies have revealed several genes that may influence bill morphology, but the similarity of gene and allele effects between species and populations is unknown. Here, we develop a custom 200K SNP array and use it to examine the genetic basis of bill morphology in 1857 house sparrow individuals from a large-scale, island metapopulation off the coast of Northern Norway. We found high genomic heritabilities for bill depth and length, which were comparable with previous pedigree estimates. Candidate gene and genome wide association analyses yielded six significant loci, four of which have previously been associated with craniofacial development. Three of these loci are involved in bone morphogenic protein (BMP) signalling, suggesting a role for BMP genes in regulating bill morphology. However, these loci individually explain a small amount of variance. In combination with results from genome partitioning analyses this indicates that bill morphology is a polygenic trait. Any studies of eco-evolutionary processes in bill morphology are therefore dependent on methods that can accommodate polygenic inheritance of the phenotype and molecular-scale evolution of genetic architecture

.ped file for Helgeland individuals

PLINK .ped file containing genotype information for all Helgeland individuals used in analysis