Lethal and sub-lethal effects of the salmon delousing agent dichlorvos on the larvae of the lobster ( Homarus gammarus L.) and herring ( Clupea harengus L.)

Abstract

A series of toxicity tests was conducted on larvae of lobster, Homarus gammarus, and herring Clupea harengus, to determine their sensitivities to dichiorvos (DDVP), the active ingredient of Aquagard R (Ciba-Geigy Agrochemicals, Cambridge, UK), a product administered m bath treatment to farmed fish as a treatment for sea lice ( Lepeophtheirus salmonis Krøyer and Caligus elongatus Nordmann) infestation. The respective 96-h LC50 values of 5.7 and 122 μg 1 −1 reflect the greater sensitivity of crustaceans to this organophosphorus compound. Whilst lobster larvae were sensitive to extended exposure at low concentrations of DDVP they were able to recover from extended exposure to sublethal concentrations. They were also able to tolerate and recover from repeated 1-h exposures to concentrations of up to 100 μg 1 −1. Lobster acetylcholinesterase activity was sensitive to inhibition by DDVP at sub-lethal concentrations. The environmental implications of the available data are discussed.