PestPuls - Effects of pulsed exposure to combinations of pesticides used as anti-parasitic medicines in aquaculture

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2017

End date

12/31/2019

Budget

938,490 EUR

Fundings

Abstract

Even if the aquaculture industry increasingly uses mechanical delousing and cleaner fish, chemical delousing is still used. Combinations of chemicals are also used as treatment, and since the chemicals are discharged directly to the ocean after use, marine organisms living in areas with salmon farms could be exposed repeatedly to pulses of mixtures of chemicals. The main aim is to provide new knowledge about the effects of exposure to pulses with low concentrations of chemicals used in bath treatment of salmon on the ecologically and commercially important Northern shrimp Pandalus borealis. The Paramove treatment solution for salmon contains 1500 mg/L hydrogen peroxide (H2O2). Increased mortality and reduced feeding rate were observed for ovigerous shrimp after exposure to three 2-hour pulses of 1.5 mg/L H2O2. None of the females lost their eggs during the exposure. The embryo exposure did not cause increased mortality of larvae 12 days after hatching. Increased mortality of adult shrimp was also observed after one 2-hour pulse of 15 mg/L. Mortality occurred around three days after the first pulse (delayed effect). Gill damage and evidence of lipid peroxidation in the hepatopancreas was documented after one-hour exposure to 1.5 mg/L and 15 mg/L hydrogen peroxide. Increased mortality and delayed development time for shrimp larvae was observed after nine days of pulsed exposure to 1.5 mg/L H2O2. One pulse (2 h) of exposure to 1.5 mg/L H2O2 caused no effects on mortality nor development time, but a significant temporary induction of gene expression associated with the organism's oxidative stress protection was observed in addition to permanent sublethal effects. We have tested the effects of short-term pulses of two commercially available anti-parasitic bath treatments Alpha Max (active ingredient deltamethrin) and/or Salmosan (active ingredient azamethiphos) on the shrimp. The Alpha Max treatment solution for salmon contains 2 microgram deltamethrin per liter. When adult shrimp were exposed to a 1000 times lower concentration (2 ng/L) they became immobilized or died after less than 24 hours exposure. When ovigerous shrimp were exposed for 2 hours per day for a week they survived, but the feeding rate was significantly reduced during and after the exposure. None of the females lost their eggs during the exposure. The embryo exposure caused significantly reduced survival of larvae 12 days after hatching. Shrimp larvae were even more sensitive to Alpha Max than the adult shrimp. High mortality of larvae was observed after exposure to 2 ng/L for two hours, and few of the survivors were able to swim. The swimming behavior of adult shrimp exposed for 24 hours to 0.2 ng/L was also affected, but this low concentration did not affect survival after 24 hours exposure. The Salmosan treatment solution for salmon contains 100 microgram azamethiphos per liter. There was no mortality of adult shrimp exposed for 24 hours to a 1000 times diluted treatment concentration for salmon (100 ng/L azamethiphos), but there was a transient increase in swimming activity. Two hours exposure per day to 100 ng/L did not affect mortality, swimming activity or feeding rate for adult shrimp, but tissue damage was detected in the hepatopancreas. There was no clear effect on mortality of shrimp larvae exposed to 100 ng/L azamethiphos for two hours once or three times or for larvae exposed as embryos. Similar effects were observed for shrimp exposed to Alpha Max and a combination of Alpha Max and Salmosan. There was, however, more severe tissue damage in the combined exposure than in adult shrimp exposed to just one of the chemicals. The tissue concentrations of deltamethrin and azamethiphos in adult shrimp was below the detection limit in most samples. Hence, it will not be possible with the current analytical methods to monitor these compounds in shrimp in the field. It is not possible to measure H2O2 in the shrimp. The main conclusion is that a few hours exposure to Alpha Max (2 ng/L deltamethrin) or Paramove (1.5 mg/L hydrogen peroxide) caused significantly increased mortality of shrimp. This is 1000 times lower concentrations than those used for delousing of salmon. Results from the lab experiments together with reported estimates of dispersion plume concentrations of discharged chemicals indicate that toxic concentrations could reach shrimp several kilometers from a treated salmon farm. Modelling performed in the project shows that there is risk for reduced shrimp populations in areas where H2O2 is used for delousing salmon. PestPuls is led by NORCE with NIVA, the University of Leicester, DEBtox Research and Burridge Consulting Inc. as project partners. In addition, Akvaplan-niva has been involved in the modelling work. PestPuls has a national advisory board with representatives from the authorities, the aquaculture industry and the fishermen's association.