Evaluating non‐lethal and latent effects of the anti‐sea lice pesticide azamethiphos on larvae and adults of the American lobster ( Homarus americanus )

Abstract

Both the American lobster fishery and salmon aquaculture are important to the economy of Atlantic Canada. Where these industries operate in proximity, research is needed to better understand any interactions and their possible effects. This study explored the effects of azamethiphos on survival and development of larval American lobsters, Homarus americanus, using exposures that reflect concentrations and durations of azamethiphos (anti‐sea lice therapeutant used in salmon aquaculture) that can be found in the environment following treatment. In adult trials, we recorded the survival and behaviour of individuals consecutively exposed to short pulses of low concentrations of azamethiphos for a period of 1 to 4 days. Larvae from all stages (I‐IV) exhibited an immobilization response when exposed to azamethiphos and that the concentration of azamethiphos that results in a 50% increase in immobilization decreases at increasing exposure time and was as low as 2.9 μgL−1 for a 3 h exposure. After exposure, we registered mortality occurring within 5 days and during the moulting window. In the larval trials the concentration required to reduce the acetylcholinesterase (AChE) activity by 50% increased from stages I to III. In the trials conducted with adults, we observed no mortality over 21 days, but did record an increase in aggressive behaviour with an increasing number of exposures. The temporal overlap between the release of larval lobster stages and the use of azamethiphos is important to consider when assessing potential risk.