Canadian Science Advisory Secretariat (CSAS) Research Document 2013/050 National Capital Region A review of potential environmental risks associated with the use of pesticides to treat Atlantic salmon against infestations of sea lice in southwest New Brunswick, Canada Dr. Les Burridge Fisheries and Oceans Canada, St. Andrews Biological Station, 531 Brandy Cove Road, St. Andrews, NB, E5B 2L9 August 2013 Foreword This series documents the scientific basis for the evaluation of aquatic resources and ecosystems in Canada. As such, it addresses the issues of the day in the time frames required and the documents it contains are not intended as definitive statements on the subjects addressed but rather as progress reports on ongoing investigations. Research documents are produced in the official language in which they are provided to the Secretariat. Published by: Fisheries and Oceans Canada Canadian Science Advisory Secretariat 200 Kent Street Ottawa ON K1A 0E6 http://www.dfo-mpo.gc.ca/csas-sccs/ [email protected] © Her Majesty the Queen in Right of Canada, 2013 ISSN 1919-5044 Correct citation for this publication: Burridge, L. 2013. A review of potential environmental risks associated with the use of pesticides to treat Atlantic salmon against infestations of sea lice in southwest New Brunswick, Canada. DFO Can. Sci. Advis. Sec. Res. Doc. 2013/050. iv + 25 p. ii TABLE OF CONTENTS ABSTRACT ............................................................................................................................... III RÉSUMÉ .................................................................................................................................. IV INTRODUCTION ....................................................................................................................... 1 SEA LICE BIOLOGY .................................................................................................................. 2 THERAPEUTANTS IN USE ....................................................................................................... 3 SALMOSAN® ......................................................................................................................... 4 Efficacy and Mechanism of Action of Azamethiphos .......................................................... 4 Distribution and Fate of Azamethiphos ............................................................................... 5 Biological Effects of Salmosan® (Azamethiphos) ................................................................ 6 Biological effects of Salmosan® (unpublished results) ........................................................ 7 Field Studies with Salmosan® ............................................................................................. 8 ALPHAMAX® .......................................................................................................................... 9 Efficacy and Mechanism of Action of Deltamethrin ............................................................. 9 Distribution and Fate of Deltamethrin ................................................................................. 9 Biological Effects of AlphaMax® and Deltamethrin (published) ..........................................10 Biological effects of AlphaMax® (unpublished results) .......................................................10 PARAMOVE® 50 ...................................................................................................................13 Efficacy and Mechanism of Action of Hydrogen Peroxide .................................................13 Distribution and Fate of Hydrogen Peroxide ......................................................................14 Biological Effects of Hydrogen Peroxide (published) .........................................................14 Biological Effects of Hydrogen Peroxide (unpublished results) ..........................................15 DISCUSSION ...........................................................................................................................16 FUTURE WORK/KNOWLEDGE GAPS ....................................................................................20 ACKNOWLEDGEMENTS .........................................................................................................21 REFERENCES .........................................................................................................................22 ii ABSTRACT Recently, pesticide bath treatments have been used in southwest New Brunswick in order to control sea lice on farmed Atlantic salmon in open netpens. As part of the emergency registrations for anti-sea lice bath treatments, Health Canada’s Pest Management Regulatory Agency was seeking additional information on the biological effects of pesticides on non-target organisms. This review analyzed three pesticides evaluated for their biological effects on non- target organisms were: Salmosan® (active ingredient: azamethiphos), AlphaMax® (active ingredient: deltamethrin), and Paramove® 50 (active ingredient: hydrogen peroxide); however, only Salmosan® and Paramove® 50 are currently being used. This review found that in lab studies, acute lethal toxicity varied with the pesticide, the non-target species, and the life stage. Azamethiphos (active ingredient in Salmosan®) is a neurotoxin, and the formulation is soluble in water and therefore unlikely to accumulate in sediment or bioaccumulate in tissue. In acute lethal toxicity tests, adult lobster and shrimp were the most susceptible species to -1 azamethiphos (48-h LC50 for adult lobster: 1.39 µg azamethiphos L ; 96-h LC50 for Mysids: 0.52 µg azamethiphos L-1), while adult lobsters repeatedly exposed to below prescribed treatment concentrations showed sublethal behavioural effects, such as affecting reproduction in females. Deltamethrin is a synthetic pyrethroid which interferes with nerve membrane function and is -1 known to be highly toxic to crustaceans (96-h LC50: for adult lobsters - 1.4 ng L ; stage III and IV lobster larvae - 3.7 – 4.9 ng L-1 and 28.2 ng L-1, respectively; amphipods – between 1.7 and 8.0 ng L-1). It has low solubility in water and due to its high lipophilicity and adsorption coefficients can persist in sediments. It is rapidly metabolized by fish and therefore unlikely to accumulate in tissues. The hydrogen peroxide in Paramove® 50 forms bubbles in the gut and haemolymph to paralyze muscles, which causes sea lice to float to the water surface. It is fully miscible in water, does not persist or bioaccumulate, and degrades to oxygen and water in about 7 days. There is little information on the toxicity of hydrogen peroxide to marine organisms. Bath treatments against sea lice have been inconsistent and effectiveness is dependent on water temperature. In summary, in laboratory lethal toxicity tests with active ingredients, lobsters were consistently more sensitive to therapeutants than Crangon and Mysid ® shrimps tested. The degree of toxicity was therapeutant specific with Paramove 50 being the ® least toxic of the three formulations tested, while AlphaMax was the most toxic. iii Examen des risques environnementaux potentiels liés à l'utilisation de pesticides pour traiter le saumon de l'Atlantique contre les infestations de pou du poisson dans le sud- ouest du Nouveau-Brunswick, au Canada RÉSUMÉ Récemment, des bains thérapeutiques de pesticides ont été utilisés dans le sud-ouest du Nouveau-Brunswick pour lutter contre les infestations de pou du poisson sur le saumon de l'Atlantique élevé dans des filets en eau libre. Dans le cadre des homologations d'urgence des bains thérapeutiques contre le pou du poisson, l'Agence de réglementation de la lutte antiparasitaire (ARLA) souhaitait obtenir des données supplémentaires sur les effets biologiques des pesticides sur les organismes non ciblés. Pour cet examen, on a analysé les effets biologiques de trois pesticides sur des organismes non ciblés : Salmosan® (ingrédient actif : azaméthiphos), AlphaMax® (ingrédient actif : deltaméthrine) et Paramove® 50 (ingrédient actif : peroxyde d'hydrogène). Toutefois, on n'utilise actuellement que Salmosan® et Paramove® 50. L'examen a permis de constater que, dans les essais de laboratoire, la toxicité aiguë létale variait selon le pesticide, les espèces non ciblées et le stade biologique. L'azaméthiphos (ingrédient actif du Salmosan®) est une neurotoxine dont la formulation est soluble dans l'eau, ce qui rend improbable son accumulation dans les sédiments ou sa bioaccumulation dans les tissus. Dans les essais de toxicité aiguë létale, les homards et les crevettes adultes étaient les espèces les plus vulnérables à l'azaméthiphos (48 h CL50 pour le homard adulte : 1,39 µg -1 -1 d'azaméthiphos l ; 96 h CL50 pour les mysidacés : 0,52 µg d'azaméthiphos l ) tandis que les homards adultes exposés à des concentrations inférieures aux concentrations prescrites pour le traitement affichaient des effets comportementaux sublétaux affectant, par exemple, la reproduction pour les femelles. La deltaméthrine est un pyréthroïde synthétique qui nuit à la fonction de la membrane des fibres nerveuses et dont la toxicité pour les crustacés est bien -1 connue (96 h CL50: pour les homards adultes : 1,4 ng l ; larves de homard de stade 3 et 4 : respectivement de 3,7 à 4,9 ng l-1 et 28,2 ng l-1; amphipodes : de 1,7 à 8.0 ng l-1). En raison de sa faible solubilité et de ses coefficients élevés d'adsorption et de lipophilie, la deltaméthrine peut demeurer dans les sédiments. 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