Influence of organs, body size and growth on domoic acid depuration in the king scallop, Pecten maximus

Since 1995, European fisheries of Pecten maximus faced the presence of Pseudo-nitzschia species, which are able to produce the neurotoxin domoic acid responsible for Amnesic Shellfish Poisoning (ASP). As filter-feeders, scallops can accumulate and retain domoic acid much longer than most of the other bivalves, from months to years. When concentrations exceed the regulatory threshold, fisheries are closed leading to economic crisis. Inter-individual variability increases the difficulty to predict the depuration dynamics. Quantifying the correlations between domoic acid depuration in P. maximus and individual physiological traits, particularly body size, could improve the understanding of contamination and depuration. In this study, toxin dynamics in organs were analysed and the effects of body size and growth were assessed. This analysis was based on two datasets, one experimental and one in situ, of depuration monitoring of P. maximus exposed to a natural bloom of toxic P. australis. Results show that the distribution of domoic acid shifted among organs between the contamination and after two months of depuration. Toxin concentrations negatively correlate with body size during contamination and after two months of depuration, but shift to a positive correlation after 7 months of depuration. This shift suggests that smaller scallops accumulate more domoic acid and depurate it faster. Thus, dilution by growth can explain the reversal of the correlation between domoic acid and body size throughout depuration. These results yield useful information for modelling such mechanisms, providing valuable tools for scallop fishery management facing ASP.