The world-wide distribution of squid has led researchers to propose that these animals be used for biomonitoring of persistent organic chemicals in the open ocean. However, their utility as a bioindicator species has not been examined in detail. The present study examined the accumulative characteristics of organochlorine compounds (OCs) in the Japanese common squid Todarodes pacificus. Sampling was done in the Japan Sea and East China Sea, with a focus on whether contaminant levels in squid reflected those in surface waters at particular sampling sites. Accumulation of OCs was primarily in the liver, and concentrations did not vary with stage of maturation of the animals. This suggests that an apparent equilibrium of OCs between liver and seawater may occur in a relatively short time at each sampling area. Moreover, we found that it may be possible to estimate the concentrations of OCs in seawater from levels of α-HCH and PCB congener (Cl5–Cl9) in squid liver, because concentrations of these compounds in squid liver displayed a significant linear correlation with concentrations in seawater of 1-2 later years at almost the same area.
The present study indicates that the Squid Watch program using T. pacificus can be a useful biomonitoring method to estimate OCs levels in surface seawater of the open ocean.