Warm water treatment increased mortality risk in salmon

Thermal treatment is a controversial method to control sea lice in the Atlantic salmon farming industry. This study aimed to complement the growing evidence base to document the impact of thermal treatments on salmon welfare, behaviour, physiology and health. Here, fish were treated two times (four weeks apart) for 30 s in either 27, 30, or 33 °C warm water, and parameters were compared to a procedural control (exposed to their holding temperature of 14 °C) or a negative control (where no treatments were applied). The fish had a clear behavioural response to the warm water, despite low difference between treatment and holding temperature (Δt = 13, 16 or 19 °C). Eye damages were more prevalent in the warm water treated groups than in the controls. Little difference was recorded between treatment groups in their growth and condition factor, blood plasma values, organ health, and long-term coping ability. There was, however, a significant increase in mortality as a function of temperature after the first treatment (14 °C: 6.5%, 27 °C: 5.3%, 30 °C: 12.4% and 33 °C: 18.9% mortality). The first treatment was performed only two weeks after the fish had been tagged and moved into the experimental holding tanks, while the fish had been allowed to recover for four weeks without any handling before the second treatment. The group of fish that were not subjected to any treatments (the negative control) had no mortality throughout the entire experimental period.publishedVersio

Effekt på dyrevelferd av gjentatte termiske behandlinger med ulik Δt, ulik utgangstemperatur og ulik behandlingstemperatur

Formålet med forsøkene i arbeidspakke 2 i TermVel-prosjektet var å avdekke effekt på dyrevelferd av gjentatt termisk behandling av laks gitt ulik utgangstemperatur, ulik behandlingstemperatur og ulik Δt (differanse mellom behandlingstemperatur og utgangstemperatur). Dette inkluderte å studere atferds-respons under behandling, skader etter behandling, fysiologiske reaksjoner og eventuelle langtidseffekter av behandling. Arbeidspakken bestod av to parallelle studier, der det ene studiet ble utført på Havforskningsinstituttet sin forskningsstasjon i Matre og det andre på Nord universitet sin forskningsstasjon i Mørkvedbukta. Begge studiene benyttet relativt stor laks (1-2 kg) som først ble individmerket og deretter plassert i forsøkskarene i et såkalt «common-garden»-oppsett. Vanntemperaturen i forsøkskarene var 14 °C i forsøket i Matre, mens vanntemperaturen var 8 °C i forsøket ved Mørkvedbukta forskningsstasjon. To til tre uker etter merking og overføring til forsøkskarene ble fiskene sortert ut basert på individmerkene og behandlet på enten samme temperatur som i karene, eller eksponert til vann på enten 27, 30 eller 33 °C i 30 sekunder. Denne eksponeringen ble så gjentatt etter 1 måned.publishedVersio

Lice shielding skirts through the decade: Efficiency, environmental interactions, and rearing challenges

Lice shielding skirts are a preventative measure against salmon lice in Atlantic salmon farming. The skirt is wrapped around the top meters of the net cage to divert the current flow around the cage, and thereby keep the salmon lice out. Despite these skirts being used actively in Norwegian aquaculture for the past decade, there is no standardised way of using them, and therefore type, depth and operating procedures vary between sites. The academic literature on the lice shielding efficiency of these skirts is not extensive and reported efficiency varies across studies and sites with some reporting favourable results, while others find none. Some also report of welfare related issues, with dissolved oxygen levels being the most prevalent, but this too varies across sites and through the production cycle. The aim of this paper is to provide a comprehensive overview and summary of relevant academic and grey literature from the last decade to identify knowledge gaps that must be filled to achieve optimal use of lice shielding skirts. This paper focuses on three main topics: lice shielding efficiency, interaction with the current flow and rearing challenges. The positive results from some sites indicate that skirts have potential as a tool against salmon lice, however, to create a best practice recommendation for skirt use, more knowledge is necessary on the interaction between skirt and the environment, and sufficient monitoring procedures and decision-making tools must be established.publishedVersio

Viral and bacterial diseases of Atlantic cod Gadus morhua, their prophylaxis and treatment: a review

This review summarises the state of knowledge of both viral and bacterial diseases of Atlantic cod Gadus morhua, and their diagnosis, prophylaxis and treatment. The most important losses have been at the larval and juvenile stages, and vibriosis has long been the most important bacterial disease in cod, with Listonella (Vibrio) anguillarum dominant among pathogenic isolates. Vaccination of cod against pathogens such as L. anguillarum and Aeromonas salmonicida clearly demonstrates that the cod immune system possesses an effective memory and appropriate mechanisms sufficient for protection, at least against some diseases. Well-known viruses such as the nodavirus that causes viral encephalopathy and retinopathy (VER), infectious pancreatic necrosis virus (IPNV) and viral haemorrhagic septicaemia virus (VHSV) have been isolated from Atlantic cod and can be a potential problem under intensive rearing conditions. No commercial vaccines against nodavirus are currently available, whereas vaccines against IPNV infections based upon inactivated virus as well as IPNV recombinant antigens are available. A number of investigations of the pharmacokinetic properties of antibacterial agents in cod and their efficacy in treating bacterial infections have been reviewed

Warm water treatment increased mortality risk in salmon

Thermal treatment is a controversial method to control sea lice in the Atlantic salmon farming industry. This study aimed to complement the growing evidence base to document the impact of thermal treatments on salmon welfare, behaviour, physiology and health. Here, fish were treated two times (four weeks apart) for 30 s in either 27, 30, or 33 °C warm water, and parameters were compared to a procedural control (exposed to their holding temperature of 14 °C) or a negative control (where no treatments were applied). The fish had a clear behavioural response to the warm water, despite low difference between treatment and holding temperature (Δt = 13, 16 or 19 °C). Eye damages were more prevalent in the warm water treated groups than in the controls. Little difference was recorded between treatment groups in their growth and condition factor, blood plasma values, organ health, and long-term coping ability. There was, however, a significant increase in mortality as a function of temperature after the first treatment (14 °C: 6.5%, 27 °C: 5.3%, 30 °C: 12.4% and 33 °C: 18.9% mortality). The first treatment was performed only two weeks after the fish had been tagged and moved into the experimental holding tanks, while the fish had been allowed to recover for four weeks without any handling before the second treatment. The group of fish that were not subjected to any treatments (the negative control) had no mortality throughout the entire experimental period

Warm water treatment increased mortality risk in salmon

Thermal treatment is a controversial method to control sea lice in the Atlantic salmon farming industry. This study aimed to complement the growing evidence base to document the impact of thermal treatments on salmon welfare, behaviour, physiology and health. Here, fish were treated two times (four weeks apart) for 30 s in either 27, 30, or 33 °C warm water, and parameters were compared to a procedural control (exposed to their holding temperature of 14 °C) or a negative control (where no treatments were applied). The fish had a clear behavioural response to the warm water, despite low difference between treatment and holding temperature (Δt = 13, 16 or 19 °C). Eye damages were more prevalent in the warm water treated groups than in the controls. Little difference was recorded between treatment groups in their growth and condition factor, blood plasma values, organ health, and long-term coping ability. There was, however, a significant increase in mortality as a function of temperature after the first treatment (14 °C: 6.5%, 27 °C: 5.3%, 30 °C: 12.4% and 33 °C: 18.9% mortality). The first treatment was performed only two weeks after the fish had been tagged and moved into the experimental holding tanks, while the fish had been allowed to recover for four weeks without any handling before the second treatment. The group of fish that were not subjected to any treatments (the negative control) had no mortality throughout the entire experimental period