Functional feed for Atlantic salmon (Salmo salar L.). Effect on gastrointestinal tract during parr-smolt transformation and susceptibility to infectious pancreatic necrosis virus (IPNV)

Atlantic salmon (Salmo salar L.) aquaculture is a relatively new industry in Norway, dating back to the 1960s. It has since then developed in to a profitable industry. Continuous improvement of hygiene control, knowledge of fish nutrition and health has been important for this development. Fish nutrition is a research field that has been increasingly focused on partly due to more use of plant raw materials as substitute for the less sustainable marine sources. The search for feed components meeting the nutritional requirements, improving fish health, growth and disease resistance is continuous. Feed producers produce functional feed by implementing functional ingredients that have positive effect on the fish. In this study, Atlantic salmon were fed a control diet and two different functional feeds during the parr-smolt transformation in freshwater and subsequently in seawater. The feed effects on the salmon gastrointestinal (GI) tract were investigated using light microscopy combined with a qualitative histological scoring system and real time polymerase chain reaction (PCR). Results from the histological analyses showed that feeding salmon with functional feeds produces less morphological changes to the GI tract compared to the control diet. The relative expression of pro- and anti-inflammatory genes was low during both periods. A mortality test using an Infectious pancreatic necrosis virus (IPNV) cohabitant challenge model revealed a significantly lower susceptibility and mortality in fish fed the functional diet. Numerous morphological observations were done during the histological examination from the feed- and challenge trial. Furthermore IPNV were detected by immunolabeling and transmission electron microscopy in pyloric caeca and distal intestine enterocytes. The results of this study showed that salmon fed a diet containing added vitamins, prebiotics, nucleotides and beta-glucans during the parr-smolt transformation period had significantly better gut status than the control diet two weeks post seawater transfer. The functional feed fed during the freshwater period contributed to significantly lower susceptibility to IPNV post seawater transfer

Effect of Season and Increased Temperature on Survival, Roe Enhancement, and Reproductive Cycle of the Green Sea Urchin (Strongylocentrotus droebachiensis) Collected from Four Relatively Close Sites in Northern Norway

A series of three trials were conducted in the North of Norway at different times of the year. The trials consisted of harvesting sea urchins from four sites, situated within 5 km of each other and then holding them in land-based enhancement facilities. They were held at ambient seawater temperatures as well as ambient plus 3.0°C. Samples were taken from the wild at the time of collection and at the end of the enhancement period as well as from the enhanced sea urchins from each site. Results showed that utilising the sea urchins from a variety of sites, even from areas where there is an abundance of sea urchins (sea urchin barrens) and the Gonad Index (GI) is almost always low, is viable in terms of the final, post roe enhancement GI. The results of the study indicate that differences in initial and final GI and the increase in GI between the sites, despite the relatively close proximity, show site selection is most likely not as important as ease of harvesting and sea urchin availability and the positive environmental impact from removal of sea urchins and these are the factors that harvesting strategies should focus on. The study has shown that it is possible to have a relatively consistent roe enhancement from S. droebachiensis from the North of Norway regardless of seasonality (time of year), site selection, and initial GI. Relatively small changes (up to 3°C) in the seawater temperature appear to have a slightly negative impact on enhancement efforts. However, this may vary when larger differences in temperature are experienced.Effect of Season and Increased Temperature on Survival, Roe Enhancement, and Reproductive Cycle of the Green Sea Urchin (Strongylocentrotus droebachiensis) Collected from Four Relatively Close Sites in Northern NorwaypublishedVersio

Effects of weathered polyethylene microplastic ingestion on sexual maturation, fecundity and egg quality in maturing broodstock Atlantic cod Gadus morhua

Microplastics (MPs) have become a global issue as they are omnipresent in the ocean. Fish ingesting MPs through feed could be affected in their physiological function, e.g., disrupted enzyme production and function, reduction of feeding and reproductive failure. This study assessed the effects of feed containing naturally weathered MPs from the Oslofjord (Norway) on the reproductive physiology of Atlantic cod (Gadus morhua). Farmed cod broodstock were fed either control (C-diet) or feeds containing 1% microplastic (MP-diet) starting nine months prior to spawning, from June until May. No major differences were found between diet groups in overall biometrics or gonad histology. Sex steroid levels (testosterone, 11-ketotestosterone and 17β-estradiol) resulted in expected profiles increasing over time without any significant differences between treatments. Gene expression levels of the steroidogenic enzyme 20β-hydroxysteroid dehydrogenase (20β-hsd) and vitellogenin1 (vtg1) showed significant differences between dietary treatments with lower expression in the control group. This can be a direct effect of MPs, but endocrine disrupting effects of potentially leachable plastic additives cannot be completely ruled out. Thus, these enzymes could be indicators of exposure to contaminants that disrupt sexual maturation by affecting the production of primarily maturation-inducing steroid. Although the concentration of MPs employed in this study may not be high enough to elicit any observable short-term biological effects, the observed gene expression suggests that long-term consequences should be considered caused by an expected increase of MPs in marine environments

Climate change with increasing seawater temperature will challenge the health of farmed Atlantic Cod (Gadus morhua L.)

Aquaculture is one of the fastest growing food production sectors in the world and further expansion is expected throughout the 21st century. However, climate change is threatening the development of the sector and action is needed to prepare the industry for the coming challenges. Using downscaled temperature projections based on the Intergovernmental Panel on Climate Change (IPCC) climate projection (Shared Socioeconomic Pathway, SSP2-4.5), we analysed potential future temperatures at a selected Atlantic cod (Gadus morhua L.) farm site in Northern Norway. Results showed that the farming area may experience increased temperatures the next 10–15 years, including more days with temperatures above 17°C. Based on the predicted future conditions, we designed a study with Atlantic cod (Gadus morhua L.) to evaluate effects from high temperature alone and in combination with Fransicella noatunensis infection. Fish were kept at 12°C and 17°C for eight weeks and samples of skin and spleen collected at different timepoints were analysed with transcriptomics, histology, scanning electron microscopy and immunohistochemistry. Results showed that high temperature had a stronger effect on the barrier functions of skin than the infection. Increased temperature induced gene expression changes in skin and spleen, heat shock protein 47 and cold inducible RNA binding protein were identified as potential gene markers for thermal stress. The effect of bacterial challenge was small at 12°C. At high temperature, the development of severe pathology in spleen coincided with a significant decrease of immunoglobulins transcripts, which contrasted with the activation of multiple immune genes. In addition, we used an in vitro model of skin biopsies and scale explants exposed to hydrogen peroxide (H2O2) to assess the effects of thermal and oxidative stress. High temperature and H2O2 reduced proliferation and migration of keratocytes, and increased expression of stress markers, and compounding effects were observed with combined stressors. Results suggest that the projected increased seawater temperature will pose a significant threat to Norwegian cod farming, affecting various biological processes and making fish more vulnerable to stressors and pathogens. Cod farming needs high attention to temperature changes, and special precautions should be taken if the temperature increases beyond cods’ thermal optimum

Functional feed for Atlantic salmon (Salmo salar L.). Effect on gastrointestinal tract during parr-smolt transformation and susceptibility to infectious pancreatic necrosis virus (IPNV)

Atlantic salmon (Salmo salar L.) aquaculture is a relatively new industry in Norway, dating back to the 1960s. It has since then developed in to a profitable industry. Continuous improvement of hygiene control, knowledge of fish nutrition and health has been important for this development. Fish nutrition is a research field that has been increasingly focused on partly due to more use of plant raw materials as substitute for the less sustainable marine sources. The search for feed components meeting the nutritional requirements, improving fish health, growth and disease resistance is continuous. Feed producers produce functional feed by implementing functional ingredients that have positive effect on the fish. In this study, Atlantic salmon were fed a control diet and two different functional feeds during the parr-smolt transformation in freshwater and subsequently in seawater. The feed effects on the salmon gastrointestinal (GI) tract were investigated using light microscopy combined with a qualitative histological scoring system and real time polymerase chain reaction (PCR). Results from the histological analyses showed that feeding salmon with functional feeds produces less morphological changes to the GI tract compared to the control diet. The relative expression of pro- and anti-inflammatory genes was low during both periods. A mortality test using an Infectious pancreatic necrosis virus (IPNV) cohabitant challenge model revealed a significantly lower susceptibility and mortality in fish fed the functional diet. Numerous morphological observations were done during the histological examination from the feed- and challenge trial. Furthermore IPNV were detected by immunolabeling and transmission electron microscopy in pyloric caeca and distal intestine enterocytes. The results of this study showed that salmon fed a diet containing added vitamins, prebiotics, nucleotides and beta-glucans during the parr-smolt transformation period had significantly better gut status than the control diet two weeks post seawater transfer. The functional feed fed during the freshwater period contributed to significantly lower susceptibility to IPNV post seawater transfer

A Guide to the Sea Urchin Reprodctive Cycle and Staging Sea Urchin Gonad Samples - Second Edition

publishedVersio

Effect of starvation on the survival, injury, and weight of adult snow crab, Chionoecetes opilio

submittedVersio

Impact of germ cell ablation on the activation of the brain–pituitary–gonadal axis in precocious Atlantic salmon (Salmo salar L.) males

The germ cells are essential for sexual reproduction by giving rise to the gametes, but the importance of germ cells for gonadal somatic functions varies among vertebrates. The RNA‐binding dead end (Dnd) protein is necessary for the specification and migration of primordial germ cells to the future reproductive organs. Here, we ablated the gametes in Atlantic salmon males and females by microinjecting dnd antisense gapmer oligonucleotides at the zygotic stage. Precocious maturation was induced in above 50% of both germ cell‐depleted and intact fertile males, but not in females, by exposure to an off‐season photoperiod regime. Sterile and fertile males showed similar body growth, but maturing fish tended to be heavier than their immature counterparts. Pituitary fshβ messenger RNA levels strongly increased in maturing sterile and fertile males concomitant with the upregulated expression of Sertoli and Leydig cell markers. Plasma concentrations of 11‐ketotestosterone and testosterone in maturing sterile males were significantly higher than the basal levels in immature fish, but lower than those in maturing fertile males. The study demonstrates that germ cells are not a prerequisite for the activation of the brain–pituitary–gonad axis and sex steroidogenesis in Atlantic salmon males, but may be important for the maintenance of gonadal somatic functions