Lethal and Sublethal Effects of the Anti-sea Lice Formulation Salmosan® on the Pacific Spot Prawn (Pandalus Platyceros)

The effects of the aquaculture chemotherapeutant Salmosan® (active ingredient [a.i.]: azamethiphos) were examined in Pacific spot prawns (Pandalus platyceros) at three temperatures (5, 11, and 17°C). Post-molt prawns were more sensitive to Salmosan® than intermolt prawns; repeated (3x) 1-hr LC50 values for post-molt prawns ranged from 17 (9.3–31 95% confident intervals) to 40 (25–63) μg/L a.i. while intermolt prawns survived 3 × 1-hr exposures up to 100 μg/L a.i. Using LC50 values, Salmosan® was approximately 2.4 times more toxic at 17 versus 5°C. Temperature significantly altered chemosensory and locomotory behaviors in intermolt prawns with the highest activity at the intermediate temperature. Significant decreases in antennule flicking (84 and 104% over controls) were seen at 17°C after 3 × 1-hr pulse exposures to 50 and 100 μg/L a.i., respectively. Temperature, but not Salmosan®, affected molting success: at 17°C significantly lower survival was seen during ecdysis (60% of those at 5°C) and at 5°C, molt time was longer (41 ± 3 days) compared to 11°C (34 ± 4 days) or 17°C (21 ± 4 days). Life stage (molt status) and environmental parameters (temperature) alter the effects of Salmosan® to non-target spot prawns.