Search results for "kalatalous"
showing 10 items of 53 documents
Higher resource level promotes virulence in an environmentally transmitted bacterial fish pathogen
2017
Diseases have become a primary constraint to sustainable aquaculture, but remarkably little attention has been paid to a broad class of pathogens: the opportunists. Opportunists often persist in the environment outside the host, and their pathogenic features are influenced by changes in the environment. To test how environmental nutrient levels influence virulence, we used strains of Flavobacterium columnare, an environmentally transmitted fish pathogen, to infect rainbow trout and zebra fish in two different nutrient concentrations. To separate the effects of dose and nutrients, we used three infective doses and studied the growth of bacteria in vitro. High nutrient concentration promoted …
The Fate of Bacteriophages in Recirculating Aquaculture Systems (RAS)—Towards Developing Phage Therapy for RAS
2019
Aquaculture production has increased tremendously during the last decades, and new techniques have been developed, e.g., recirculating aquaculture systems (RAS). In RAS, the majority of water volume is circulated via mechanical and biological filters and reused in the tanks. However, the prevention and treatment of diseases in these systems are challenging, as the pathogens spread throughout the system, and the addition of chemicals and antibiotics disrupts the microbiome of the biofilters. The increasing antibiotic resistance has made phage therapy a relevant alternative for antibiotics in food production. Indeed, as host-specific and self-replicating agent they might be optimal for target…
Complementary methods assessing short and long-term prey of a marine top predator ‒ Application to the grey seal-fishery conflict in the Baltic Sea.
2019
The growing grey seal (Halichoerus grypus) population in the Baltic Sea has created conflicts with local fisheries, comparable to similar emerging problems worldwide. Adequate information on the foraging habits is a requirement for responsible management of the seal population. We investigated the applicability of available dietary assessment methods by comparing morphological analysis and DNA metabarcoding of gut contents (short-term diet; n = 129/125 seals, respectively), and tissue chemical markers i.e. fatty acid (FA) profiles of blubber and stable isotopes (SIs) of liver and muscle (mid- or long-term diet; n = 108 seals for the FA and SI markers). The methods provided complementary inf…
Genetic-based evaluation of management units for sustainable vendace (Coregonus albula) fisheries in a large lake system
2022
The goal of the processing industry, trade and consumers is to get eco-labelled freshwater fish products from sustainable fisheries into the market as soon as possible. The fourth largest natural lake system in Europe, the Saimaa lake system supports a fishery for vendace (Coregonus albula). Certification of the fishery requires an understanding of population structure to help determine the number and spatial extent of management units. In this study, we analysed the genetic diversity of local vendace populations in the Saimaa lake system and aimed to identify the conservation and management units of vendace. Within the Saimaa, the genetic divergence between local populations of vendace was…
Prevalence of genetically similar Flavobacterium columnare phages across aquaculture environments reveals a strong potential for pathogen control
2022
Intensive aquaculture conditions expose fish to bacterial infections, leading to significant financial losses, extensive antibiotic use and risk of antibiotic resistance in target bacteria. Flavobacterium columnare causes columnaris disease in aquaculture worldwide. To develop a bacteriophage-based control of columnaris disease, we isolated and characterized 126 F. columnare strains and 63 phages against F. columnare from Finland and Sweden in 2017. Bacterial isolates were virulent on rainbow trout (Oncorhynchus mykiss) and fell into four previously described genetic groups A, C, E and G, with genetic groups C and E being the most virulent. Phage host range studied against a collection of 2…
Rich resource environment of fish farms facilitates phenotypic variation and virulence in an opportunistic fish pathogen
2020
Phenotypic variation is suggested to facilitate the persistence of environmentally growing pathogens under environmental change. Here, we hypothesized that the intensive farming environment induces higher phenotypic variation in microbial pathogens than natural environment, because of high stochasticity for growth and stronger survival selection compared to the natural environment. We tested the hypothesis with an opportunistic fish pathogen Flavobacterium columnare isolated either from fish farms or from natural waters. We measured growth parameters of two morphotypes from all isolates in different resource concentrations and two temperatures relevant for the occurrence of disease epidemic…
Comparison of Delivery Methods in Phage Therapy against Flavobacterium columnare Infections in Rainbow Trout
2021
Viruses of bacteria, bacteriophages, specifically infect their bacterial hosts with minimal effects on the surrounding microbiota. They have the potential to be used in the prevention and treatment of bacterial infections, including in the field of food production. In aquaculture settings, disease-causing bacteria are often transmitted through the water body, providing several applications for phage-based targeting of pathogens, in the rearing environment, and in the fish. We tested delivery of phages by different methods (via baths, in phage-coated material, and via oral delivery in feed) to prevent and treat Flavobacterium columnare infections in rainbow trout fry using three phages (FCOV…
Screening of microalgae and LED grow light spectra for effective removal of dissolved nutrients from cold-water recirculating aquaculture system (RAS…
2019
Popularity of recirculating aquaculture systems (RAS) is increasing. Because of the high water recirculation rate, dissolved nutrients originating from fish feed are concentrated enough in RAS wastewater (WW) to enable growth of primary producers, e.g. microalgae. This study evaluated nitrate-nitrogen (NO3-N) and phosphate-phosphorus (PO4-P) removal efficiency of ten temperate zone freshwater microalgae species during their exponential growth phase in unfiltered RAS WW at 17 ± 0.5 °C. Growth and nutrient uptake efficiency of six green and four non-green microalgae strains were compared between WW and reference growth medium in batch monocultures. The effect of three different LED grow light…
Microbiome response to foam fractionation and ozonation in RAS
2022
Efficient water treatment is required to maintain high water quality and control microbial growth in recirculating aquaculture systems (RAS). Here, we examined the effects of two treatment methods, ozonation and foam fractionation, separately and combined, on the microbiology in twelve identical experimental RAS with rainbow trout (Oncorhyncus mykiss) during 8 weeks. Microbes suspended in water and growing in biofilter biofilms were examined using flow cytometry analysis and high throughput sequencing of the 16S rRNA gene. The results showed that foam fractionation did not cause large changes in abundance or overall community composition of free-living microbes. Instead, through decreasing …
Filtration of Nordic recirculating aquaculture system wastewater : Effects on microalgal growth, nutrient removal, and nutritional value
2021
Microalgal bioremediation of recirculating aquaculture system (RAS) wastewater represents an alternative for wastewater treatment with the potential to generate valuable biomass. This study evaluated the effects of removing biological contamination and suspended solids from Nordic area RAS wastewater through filtration with 0.45 μm filters on the performance and nutritional value of microalgae. All three tested green microalgae (Haematococcus pluvialis, Monoraphidium griffithii, and Selenastrum sp.) were able to grow in raw (unfiltered) and filtered RAS wastewater. Cultivation in raw RAS wastewater decreased the ω-3 and ω-6 fatty acid content of H. pluvialis as compared to filtered wastewat…