Spatial variability of domoic acid concentration in king scallops Pecten maximus off the southeast coast of Ireland

Amnesic shellfish poisoning (ASP) has proved problematic in Irish king scallop, Pecten maximus fisheries necessitating restrictions on the sale of fresh scallops (in-shell), which achieve a higher market price than frozen processed product. An investigation of variability in domoic acid (DA) concentration in king scallop from 69 sampling sites within a limited area off the southeast coast of Ireland was performed. Variation in DA concentration was examined in the whole area, within smaller sub-areas, with size, age, and water depth. Mean DA concentrations in whole scallop ranged from 6.5 to 154.3 μg g^-1, with an overall mean of 40.6 ± 30.8 μg g^-1. The concentration in gonad exceeded 20 μg g^-1 in 17 sites and in adductor muscle in 3 sites. Significant differences in DA concentration were detected between scallops from different sampling stations. Whole scallop tissue and individual scallop tissues with the exception of gonad, exhibited significant negative correlations with water depth. Highest DA concentrations were recorded in inshore, shallow sites and lowest DA concentrations in deeper offshore waters. Significant positive correlations between DA concentration in hepatopancreas and scallop size were exhibited at inshore sites but not at offshore sites. High inter-animal and spatial variability in toxin concentration demonstrated the importance of a reliable sampling protocol for the management of ASP outbreaks to ensure public safety and to avoid unnecessary fishery closures.