In European waters, significant economic damages to wooden structures are caused by bivalves molluscs and crustaceans. Treatments like copper-chrome-arsenic mixtures (CCA) were designed to prevent settlement of these wood borer species. However, limited and conflicting evidence regarding the toxicity to non-target organisms are available in the literature. This report aims to provide insights regarding the CCA leachates' toxicity to an important aquaculture species, the blue mussel Mytilus edulis for which much information on normal and stressed physiology is available for purposes of comparisons. The mussels are usually considered as a particularly suitable species for biological monitoring (Smaal and Widdows, 1994). To address the CCA leachate issue, two approaches have been developed by using a biological early waming system (Baldwin and Kramer, 1994) and by assessing the mussel scope for growth (SFG). The biological early warning system concems a valvometer monitoring continuously the valve movement response. Under normal conditions, mussels have their shells open for respiration and feeding processes. They close their shells under natural or anthropogenic stress for an extended period of time as an escape behavior response. They might also increase the valve movement activity when stressed by specific pollutants (Kramer et al., 1989). Therefore, the valve movement response has been used to study a number of pollutant effects, like trace metals and trace organics (Davenport, 1977; Sloof & al., 1983). The scope for growth (SFG) is an integrated physiological parameter reflecting the energy balance between energy acquisition (feeding - absorption) and catabolism, mainly due to respiration. This parameter has been widely used to assess environmental quality and test pollutant effects (Bayne, 1976; Bayne & al., 1985; Widdows & al., 1990). Relationsrnps between both approaches will be developed to improve understandings of CCA effects on the mussel physiology.