The Acute and Delayed Mortality of the Northern Krill (Meganyctiphanes norvegica) When Exposed to Hydrogen Peroxide

Bath treatment pharmaceuticals used to control sea lice infestations in the salmonid industry, such as hydrogen peroxide (H2O2), are released directly into the environment where non-target organisms are at risk of exposure. The aim of this study was to determine the threshold concentrations for mortality of the Northern krill, Meganyctiphanes norvegica, a major component of the north Atlantic marine ecosystem. To assess the lethal effects of H2O2, we carried out a series of 1 h acute toxicity tests and assessed mortality through a 48 h post-exposure period. One-hour exposure to 170 mg/L, corresponding to 10% of the recommended H2O2 treatment, caused 100% mortality and a subsequent acute median-lethal concentration LC50 value of 32.5 mg/L. Increased mortality was observed with time in all exposed groups, resulting in successively lower LC50 values during the post-exposure period. The suggested H2O2 concentrations have the potential of causing negative effects to the Northern krill.publishedVersio

Vurdering av helse- og miljøeffekter ved bruk av flubenzuroner ved avlusing av oppdrettsfisk

Diflubenzuron og teflubenzuron hemmer virkningen av enzymet chitinase, som løser opp kitinet. Denne prosessen er en forutsetning for at krepsdyr kan skifte skall, og dyrene dør dersom skallskiftet hindres. Alle dyr som har en chitinaseaktivitet kan bli påvirket dersom de får i seg disse stoffene, men det er særleg krepsdyr som er i faresonen

Bath treatment, an alternative method for the administration of the quinolones flumequine and oxolinic acid to halibut Hippoglossus hippoglossus, and in vitro antibacterial activity of the drugs against some Vibrio sp.

Administration of flumequine and oxolinic acid to halibut Hippoglossus hippoglossus by bath resulted in significant tissue levels of both the antibacterials. Bath treatment using 150 mg l(-1) of flumequine and 200 mg l(-1) of oxolinic acid for 72 h resulted in flumequine concentrations of 14.2 mu g g(-1) in muscle and 85.4 mu g g(-1) in abdominal organ homogenate and oxolinic acid concentrations of 9.4 mu g g(-1) in muscle and 72.6 mu g g(-1) in abdominal organ homogenate. Excretion of both antibacterials was rapid and characterised by elimination half-lives (t(1/2)) of 10 and 15.6 h respectively for flumequine and oxolinic acid in muscle and 9.8 and 15.0 h respectively in the abdominal organ homogenate. The corresponding elimination times (E(t)) were 6.5 and 8 d respectively for flumequine and oxolinic acid in muscle and 7.5 and 9 d respectively in abdominal organ homogenate when a maximum residue concentration of 0.05 mu g g(-1) was applied for both drugs. The minimum inhibitory concentration (MIG) against strains of Vibrio sp. ranged from 0.015 to 1.0 mu g ml(-1) for flumequine and 0.015 to 0.5 mu g ml-l for oxolinic acid. Following bath treatment, tissue levels of flumequine and oxolinic acid greater than MIC for susceptible strains (<0.0625 mu g ml(-1)) were maintained for up to 6.5 and 8 d respectively for flumequine and oxolinic acid in muscle and 7.5 and 9 d respectively in abdominal organ homogenate

Efficacy of orally administered oxolinic acid and Vetoquinol, an oxolinic acid ester, for the treatment furunculosis in Atlantic salmon Salmo salar held seawater

This study was performed to determine the efficacy of orally administered oxolinic acid and Vetoquinol, an oxolinic acid ester, in the treatment of experimental induced furunculosis in Atlantic salmon Salmo salar held in seawater. Two strains of the causative bacterium Aeromonas salmonicida subsp. salmonicida, 1 sensitive (VI-88/09/03175) and 1 resistant (3475/90) to oxolinic acid, were used. In 2 trials, cohabitational challenges were performed by introducing 8 fish challenged in advance by an intraperitoneal injection of 2.2 x 10(4) colony forming units of strain 3475/90 (Trial 1) or strain VI-88/09/03175 (Trial 2) to 10 aquaria each containing 40 healthy fish. The treatment groups in both trials consisted of 4 groups receiving either oxolinic acid (2 groups) or Vetoquinol (2 groups) and 1 control group. An unchallenged, unmedicated group was used to determine the natural mortality in the population. The recommended therapeutic dose of 25 mg oxolinic acid kg(-1) fish at Days 1, 2, 4, 6, 8 and 10 following initiation of treatment was used. Oral medication initiated at Day 10 (Trial 1) or Day 11 (Trial 2) following challenge significantly (p < 0.05) lowered the specific mortality in all drug-treated groups compared to the untreated control groups. Mortality in Vetoquinol-treated groups was significantly (p < 0.05) lower than in oxolinic acid-treated groups in Trial 1 whereas no significant (p < 0.05) difference in survival rate was found between the medicated groups in Trial 2

Vurdering av helse- og miljøeffekter ved bruk av flubenzuroner ved avlusing av oppdrettsfisk

Diflubenzuron og teflubenzuron hemmer virkningen av enzymet chitinase, som løser opp kitinet. Denne prosessen er en forutsetning for at krepsdyr kan skifte skall, og dyrene dør dersom skallskiftet hindres. Alle dyr som har en chitinaseaktivitet kan bli påvirket dersom de får i seg disse stoffene, men det er særleg krepsdyr som er i faresonen

Changes in plasma and liver glutathione levels in Atlantic salmon Salmo salar suffering from infectious salmon anemia (ISA)

The levels of reduced glutathione (GSH) in plasma and liver in healthy Atlantic salmon Salmo salar and salmon suffering from infectious salmon anaemia (ISA) were measured using high-performance liquid chromatography (HPLC). The infected salmon had an increased level of plasma GSH Compared to controls, the mean values being 72.31 +/- 11.56 and 52.8 +/- 2.92 muM, respectively. The increased GSH level in plasma was found to be significant (p < 0.0001, unpaired t-test) and may be a result of intracellular release. The hepatic GSH level was significantly lower in the infected salmons compared to controls (p < 0,0001, unpaired t-test) and the mean values were calculated to be 1618.7 +/- 543.7 and 2512.1 +/- 326.9 nmol g-1 liver (wet wt), respectively. A decrease in hepatic GSH of up to 70 % in diseased fish compared to controls was observed. Such low levels of GSH in the liver may affect the capability of this organ in the transformation and excretion of xenobiotics from the body

Modelling chemical releases from fish farms: impact zones, dissolution time, and exposure probability

Tarpaulin bath treatments are used in open net-pen finfish aquaculture to combat parasitic infections, in particular sea lice. After treatment, the toxic wastewater is released directly into the ocean, potentially harming non-target species in the vicinity. We model the dispersion of wastewater chemicals using a high-resolution numerical ocean model. The results are used to estimate the impact area, impact range, dissolution time, and exposure probability for chemicals of arbitrary toxicity. The study area is a fish-farming intensive region on the Norwegian western coast. Simulations are performed at 61 different release dates, each on 16 locations. In our base case where the chemical is toxic at 1% of the treatment concentration, the release of a 16000 m³ wastewater plume traverses a median distance of 1.9 km before being completely dissolved. The median impacted area is 0.9 km² and the median dissolution time is 6.8 hours. These figures increase to 5.9 km, 7.0 km², and 21 hours, respectively, if the chemical is toxic at 0.1 % of the treatment concentration. Locations within fjords have slower dissolution rates and larger impact zones compared to exposed locations off the coast, especially during summer.publishedVersio

The impact of anti-sea lice pesticides, azamethiphos and deltamethrin, on European lobster (Homarus gammarus) larvae in the Norwegian marine environment

Anti-sea lice pesticides, used in the salmonid aquaculture industry, are a growing environmental concern due to their potential to adversely affect non-target crustaceans. Azamethiphos and deltamethrin are two bath treatment pesticides used on salmon farms in Norway, however, limited information is available on their impact on European lobster (Homarus gammarus) larvae in the Norwegian marine environment. Here, we firstly report the lethal (LC50) and effective (EC50) concentrations of azamethiphos and deltamethrin for stage I and stage II larvae, following 1-h exposures. Using a hydrodynamic model, we also modelled the dispersal of both compounds into the marine environment around selected Norwegian farms and mapped the potential impact zones (areas that experience LC50 and EC50 concentrations) around each farm. Our data shows that azamethiphos and deltamethrin are acutely toxic to both larval stages, with LC50 and EC50 values below the recommended treatment concentrations. We also show that the azamethiphos impact zones around farms were relatively small (mean area of 0.04–0.2 km2), however deltamethrin impact zones covered much larger areas (mean area of 21.1–39.0 km2). These findings suggest that deltamethrin poses a significant risk to European lobster in the Norwegian marine environment while the impact of azamethiphos may be less severe.publishedVersio

Distribution and Persistence of Diflubenzuron and Teflubenzuron in the Marine Environment Around Salmonid Aquaculture Facilities

To achieve a sustainable salmonid aquaculture industry, the environmental impacts of chemicals used to treat sea lice (Caligidae) infestations need to be considered. Our ability to assess the risks associated with these treatments in relation to human and wildlife health is limited by the lack of information on their concentrations in marine coastal environments. Diflubenzuron and teflubenzuron are chitin synthesis inhibiting insecticides frequently used to treat sea lice infestations on Norwegian salmon farms. In the present study, the distribution, persistence and bioaccumulation of both compounds were assessed in marine sediments and benthic macrofauna collected at four Norwegian aquacultures sites. Both compounds were detected in sediments sampled at 30–1400 m from the selected farms and 8–22 months after the last treatments took place. Diflubenzuron was detected above the limit of quantification (LOQ) in 76% of sediment samples and measured levels ranged between 2.4 and 257 μg/kg dry weight (dw). Teflubenzuron was detected above the LOQ in 92% of sediment samples, at concentrations ranging between 1.3 and 3474 μg/kg dw. In all samples where diflubenzuron and teflubenzuron were detected, the measured levels exceeded the Norwegian environmental quality standards (EQSsediment; 0.2 and 0.0004 μg/kg dw, respectively), indicating that these compounds may pose a risk to benthic marine species living near fish farms. Both compounds were detected in wild fauna collected near the selected aquaculture sites with measured residue levels in the low micro-gramme per kilogramme wet weight range. The residue levels detected in economically important species caught for human consumption, such as pink shrimp (Pandalus montagui) and Norway lobster (Nephrops norvegicus), were substantially lower than biota EQS’s and maximum residue limits (MRL) set by the EU for salmon tissue. Further studies are needed to fully understand the ecological impacts of these compounds in the marine environment, with the potential for lethal and sub-lethal effects to occur in non-target organisms following chronic exposures.publishedVersio

Mortality in the rockpool shrimp Palaemon elegans following long-term exposure to low doses of the anti-parasitic drug Teflubenzuron

Anti-parasitic drugs used to control sea lice infestations in the salmonid aquaculture industry are a growing environmental concern due to their potential impacts on non-target crustacean species. This study examined the lethal effects of teflubenzuron, a common in-feed pharmaceutical drug used on Norwegian salmon farms, on a non-target species, rockpool shrimp Palaemon elegans, following an extended exposure period. The standard daily dose for treating salmon is 10 µg teflubenzuron g-1 fish. Adult shrimp were fed 1 of 6 low doses of teflubenzuron (0, 0.0025, 0.005, 0.05, 0.094, 0.188 and 1.88 µg g-1) twice a week for a period of 66 d. Cumulative mortality reached 15, 27, 82 and 100% amongst shrimp exposed to the highest treatment groups (0.05, 0.094, 0.188 and 1.88 µg g-1, respectively). Cumulative mortality amongst shrimp exposed to the 2 lowest teflubenzuron doses and control feed was low (5%). Dose response curves based on measured concentrations within the shrimp were used to calculate a series of lethal threshold concentrations (LCx). The LC5, LC50 and LC90 concentrations of teflubenzuron causing low, median and high levels of mortality in rockpool shrimp were estimated to be 1.2, 18.4 and 150.6 ng g-1, respectively. These concentrations are similar to those reported in wild crustacean species, including shrimp species in the vicinity of Norwegian fish farms, both during and after teflubenzuron medication, suggesting that exposure to low doses of this compound can pose a significant risk to wild shrimp populations.publishedVersio