Low concentrations of sodium hypochlorite affect population dynamics in Gyrodactylus salaris ( Malmberg, 1957): practical guidelines for the treatment of the Atlantic salmon, Salmo salar L. parasite

• Published in: Journal of Fish Diseases
• Main Authors: Hagen, A G, Hytterød, S, Olstad, K
• Other Authors: Norwegian Institute for Water Research, Norwegian Veterinary Institute, Norwegian Institute for Nature Research
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1111/jfd.12218; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fjfd.12218; https://onlinelibrary.wiley.com/doi/pdf/10.1111/jfd.12218

Abstract Atlantic salmon, S almo salar L . parr (age 1+), infected by the monogenean ectoparasite G yrodactylus salaris ( M almberg, 1957), were exposed to chlorine ( C l)‐enriched water at three different concentrations: C l low (0–5 μg Cl L −1 ), C l medium (18 μg Cl L −1 ) and C l high (50 μg Cl L −1 ). There was a negative correlation between G . salaris infections and the hypochlorite concentrations added. The parasite infection was eliminated by day 6–8 and day 2–4 in the groups C l medium and Cl high , respectively, while inhibition of G . salaris population growth was observed in the C l low group. An important note to this matter, however, is that the G . salaris specimens observed at day 6 in C l medium and at day 2 in C l high were all considered dead by subjective judgement. No mortality in the salmon parr was observed during the first 8 days of the experiment, demonstrating that C l has a stronger effect on G . salaris than on the salmonid host. The differences in sensitivity between the parasite and the A tlantic salmon indicate that hypochlorite has a potential use as a parasiticide with a therapeutic margin. The low‐dose sensitivity may imply that C l pollution in urban areas may pose a greater risk towards biodiversity than previously assumed.