The effects of the anti-sea lice chemotherapeutants Salmosan® and Interox® Paramove® 30 on marine zooplankton

Sea lice infestations can be harmful to both wild and farmed salmon. The Atlantic salmon aquaculture industry relies on the use of chemotherapeutants to control sea lice outbreaks, which can have both economic and ecological impacts. With treatment, several chemotherapeutants are released directly into the water column, potentially exposing non-target organisms. The lethal and sublethal effects of two anti-sea lice chemotherapeutants, Interox® Paramove® 30 and Salmosan®, were examined in wild zooplankton assemblages, wild brachyuran and porcelain crab zoea, and cultured marine copepods (Acartia tonsa). The lowest LC50 values for Interox® Paramove® 30 and Salmosan® of 4 mg/L (CI 4 – 6.9 mg/L) and 54 µg/L (CI 32 – 90 µg/L), respectively) were found for wild zooplankton exposed for 3-h with a 48-h recovery period. The highest Interox® Paramove® 30 LC50 value was 55 mg/L (CI 30 – 95 mg/L) for brachyuran crab zoea using a 1-h exposure, and the highest LC50 value found for Salmosan® was 529 µg/L (CI 333 – 900 µg/L) using a 1-h exposure for wild zooplankton. In terms of sublethal affects, Acartia tonsa naupliar development was more sensitive to both chemicals compared to hatching and reproductive success. After exposure to Interox® Paramove® 30 or Salmosan®, the 3-h naupliar development EC50 values were 0.12 mg/L (CI 0.08 – 0.18 mg/L) and 30 µg/L (CI 20 – 41 mg/L), respectively. The least sensitive Acartia tonsa endpoint tested was immobility after hatching: eggs exposed for 1-h to Interox® Paramove® 30 had an immobility EC50 value of 7.3 mg/L (CI 3.2 – 72 mg/L). In contrast, Salmosan® had no observable effect after a 1-h exposure of Acartia tonsa eggs up to 7500 µg/L. Collectively, these results provide novel toxicity data for two chemotherapeutants to planktonic organisms which will support the safe and appropriate regulation of these aquaculture chemicals in Canada.