Lethal and sub-lethal effects of repeated short term exposures Salmosan (A.I. azamethiphos) on the Pacific Spot Prawn, Pandalus platyceros

Abstract

Sea lice are a cause of concern in Canada, as outbreaks in fish farms have significant implications for both farmed and wild salmonid populations. The most common sea lice treatment protocols in BC call for the subsequent release of anti-sea lice chemotherapeutants directly into the water column. These chemotherapeutants have been shown to have lethal effects on non-target crustaceans such as lobsters and prawns. This project is concerned specifically with Salmosan® (A.I. azamethiphos) which has received emergency approval in Eastern Canada and may be used in BC as aquaculture site managers look for alternatives to the most common current-use product, SLICE®. However, few experiments on Salmosan® have involved species from the West Coast. Furthermore, there is a little known about sub-lethal effects. This project addresses this data gap by investigating both the lethal and sub-lethal effects of Salmosan® on Pacific spot prawns, Pandalus platyceros under environmentally relevant multiple pulse and combined stressor scenarios. Lethality tests show post-molt prawns to be significantly more sensitive to Salmosan® than inter-molt prawns, with increasing sensitivity at higher temperatures. Molting experiments suggest that temperature negatively impacts molting survival while Salmosan® has no effect on overall molting success. Preliminary behavioural data suggest that Salmosan® has no effect on olfactory behavior while high concentrations of Salmosan® may elicit an avoidance response. The results of this project can contribute to improving chemical use regulations by informing on both selection of chemotherapeutants and design of application protocols