Search results for "Fish Farming"

Priming of host resistance to protect cultured rainbow trout Oncorhynchus mykiss against eye flukes and parasite-induced cataracts

2010

In the present study, immunologically naive rainbow trout Oncorhynchus mykiss were experimentally exposed to a low-level Diplostomum spathaceum (Trematoda) infection to stimulate acquired resistance and, along with unexposed controls, were subsequently exposed to natural infection for 8 weeks. The priming of the host resistance, designed to simulate a procedure applicable in aquaculture, decreased the number of establishing parasites compared to untreated controls by the end of the experiment. This effect was slow and did not protect the fish against the parasite-induced cataracts. The results suggest that this type of priming of host resistance is probably inefficient in preventing the del…

The Influence of Infective Dose on the Virulence of a Generalist Pathogen in Rainbow Trout (Oncorhynchus mykiss) and Zebra Fish (Danio rerio)

2015

Pathogen density and genetic diversity fluctuate in the outside-host environment during and between epidemics, affecting disease emergence and the severity and probability of infections. Although the importance of these factors for pathogen virulence and infection probability has been acknowledged, their interactive effects are not well understood. We studied how an infective dose in an environmentally transmitted opportunistic fish pathogen, Flavobacterium columnare, affects its virulence both in rainbow trout, which are frequently infected at fish farms, and in zebra fish, a host that is not naturally infected by F. columnare. We used previously isolated strains of confirmed high and low …

By-products of farmed European sea bass (Dicentrarchus labrax L.) as a potential source of n-3 PUFA

2013

Total by-products (TBP) obtained by filleting farmed and wild European sea bass (Dicentrarchus labrax) were analyzed to evaluate if, on the basis of the percentage yield, total lipid content and fatty acid composition, they can be considered a resource of n-3 polyunsaturated fatty acids (PUFA). Results show that TBP from intensively farmed fish (IFF) contain higher total lipid content and have a higher level of n-3 PUFA rich in eicosapentaenoic (EPA) and docosaexaenoic acid (DHA), compared to extensively farmed fish (EFF) and to wild fish (WF) (P < 0.05). This difference may suggest a way of promotion of TBP from IFF sea bass through the n-3 PUFA recovery by extraction.

Intensive fish farming and the evolution of pathogen virulence: the case of columnaris disease in Finland.

2009

Ecological changes affect pathogen epidemiology and evolution and may trigger the emergence of novel diseases. Aquaculture radically alters the ecology of fish and their pathogens. Here we show an increase in the occurrence of the bacterial fish disease Flavobacterium columnare in salmon fingerlings at a fish farm in northern Finland over 23 years. We hypothesize that this emergence was owing to evolutionary changes in bacterial virulence. We base this argument on several observations. First, the emergence was associated with increased severity of symptoms. Second, F. columnare strains vary in virulence, with more lethal strains inducing more severe symptoms prior to death. Third, more vir…

Seasonal dynamics of egg laying and egg-laying strategy of the ectoparasite Argulus coregoni (Crustacea: Branchiura).

2004

Substrate preferences, spatial aggregation patterns and seasonal dynamics in the egg laying of ectoparasiticArgulus coregoniwere studied at a commercial fish farm in Finland. Pilot experiments showed thatA. coregonifemales selected specific types of substrates for egg laying. Significantly moreA. coregonieggs were laid on dark substrates than on light ones suggesting the use of visual cues. Therefore, egg-laying plates of dark colour were constructed for further experiments. MostA. coregonieggs were deposited in locations in shadow and in the deepest water in a 2 m deep farming canal. Relatively more eggs were laid on bottom stones situated near each egg-laying trap than on artificial egg-l…

Rearing of sharpsnout seabream (Diplodus puntazzo, Cetti 1777) in a Mediterranean fish farm: monoculture versus polyculture

2002

Outside-host growth of pathogens attenuates epidemiological outbreaks.

2012

Opportunist saprotrophic pathogens differ from obligatory pathogens due to their capability in host-independent growth in environmental reservoirs. Thus, the outside-host environment potentially influences host-pathogen dynamics. Despite the socio-economical importance of these pathogens, theory on their dynamics is practically missing. We analyzed a novel epidemiological model that couples outside-host density-dependent growth to host-pathogen dynamics. Parameterization was based on columnaris disease, a major hazard in fresh water fish farms caused by saprotrophic Flavobacterium columnare. Stability analysis and numerical simulations revealed that the outside-host growth maintains high pr…

Adaptation to host inVibrio vulnificus, a zoonotic pathogen that causes septicemia in fish and humans

2019

Vibrio vulnificus is a siderophilic pathogen spreading due to global warming. The zoonotic strains constitute a clonal-complex related to fish farms that are distributed worldwide. In this study, we applied a transcriptomic and single gene approach and discover that the zoonotic strains bypassed the iron requirement of the species thanks to the acquisition of two iron-regulated outer membrane proteins (IROMPs) involved in resistance to fish innate immunity. Both proteins have been acquired by horizontal gene transfer and are contributing to the successful spreading of this clonal-complex. We have also discovered that the zoonotic strains express a virulent phenotype in the blood of its main…

Biostimulation of in situ microbial degradation processes in organically-enriched sediments mitigates the impact of aquaculture

2019

Fish farm deposition, resulting in organic matter accumulation on bottom sediments, has been identified as among the main phenomena causing negative environmental impacts in aquaculture. An in situ bioremediation treatment was carried out in order to reduce the organic matter accumulation in the fish farm sediments by promoting the natural microbial biodegradation processes. To assess the effect of the treatment, the concentration of organic matter in the sediment and its microbial degradation, as well as the response of the benthic prokaryotic community, were investigated. The results showed a significant effect of the treatment in stimulating microbial degradation rates, and the consequen…

Development of monogenean communities on the gills of roach fry (Rutilus rutilus).

1999

The formation and development of monogenean communities on the gills of roach fry was followed in 1992 from early June to October (size range 9 to 47 mm). Roach fry (n=291) were sampled weekly from the small, humic River Rutajoki in central Finland. A further 209 roach fry were reared in a fish farm supplied by water from the river. Four Dactylogyrus species were found: D. nanus, D. crucifer, D. micracanthus and D. suecicus. Other species found on the gills were Gyrodactylus sp. and Paradiplozoon homoion. The first Dactylogyrus juvenile occurred on a 12 mm long fish fry in late June and the first adult (D. nanus) 1 week later in Tank 1. D. nanus was also the most common parasite in the rive…