Cadmium (Cd) and mercury (Hg) levels were measured in the tissue samples of two loliginid (Alloteuthis sp. and Loligo forbesi) and
two ommastrephid (Todarodes sagittatus and Todaropsis eblanae) squid species collected from research cruise and fishery (market)
samples in UK waters during 2004–05. Concentrations of Cd were generally higher in the ommastrephids, in all tissues except muscle. Hg
concentrations were higher in T. sagittatus than in the loliginids. In L. forbesi, metal concentrations differed between tissues and also
varied in relation to body size, geographic origin, and season. Cd levels decreased with increasing body size. This may be related to a shift
in the diet with growth, since small L. forbesi feed on benthic invertebrates that have relatively high Cd concentrations, whereas larger
individuals prey mainly on fish that have low Cd concentrations. Hg levels increased with body size, indicating its retention, and they
were highest at the end of the spawning season and in squid from the English Channel and the Scottish West Coast. It is likely that the
ambient concentration of Hg in seawater plays an important part in its accumulation in squid tissues. As it is a short-lived species,
L. forbesi may therefore function as a bioindicator species for Hg contamination of the marine environment. Our results indicate that
there is no significant danger to humans from consuming squid from UK waters.