Preliminary measurements of formaldehyde in seawater and edible tissues of farmed gilthead seabream after formalin immersion

This study was performed to measure the possible persistence of formaldehyde, the active substance of formalin solution, in seawater and edible gilthead seabream (Sparus aurata) tissues after a formalin bath. The trial was carried out during the summer period as parasitic infestations are of a high frequency. Water samples were taken within or at a short distance from the treatment cages, during and following formalin immersion. Fish fillets were also sampled at the same sampling points. Chromatographic analysis of water and tissue samples was performed with a photodiode array detector (HPLC-PDA). Measured formaldehyde concentrations in gilthead seabream fillets clearly showed no increase due to the immersion or advent of time. Formaldehyde measurements in seawater revealed that after formalin treatments negligible amounts of the substance remain in the aquatic environment and these values seem to be relatively unaffected by depth in the vicinity of the fish cages. Further research is required to investigate the formalin degradation cycle under Mediterranean seawater conditions, including more farm sites and temperature ranges.