Biochemical and behavioural effects of hydraulic dredging on the target species Chamelea gallina

This study is focused on evaluating biological effects on the target species Chamelea gallina as a result of repeated exploitation of clam beds by hydraulic dredging. A biomarker approach was adopted and two physiological indices were applied: adenylate energy charge (AEC) (biochemical level) and reburrowing behaviour (organism level). The aim was to investigate the biological response to various types of fishing, i.e., commercial systems using water at high pressures (HP), and experimental systems at lower pressures (LP) in the field, and to evaluate the response of clams to mechanical stress in the laboratory. Field results showed that HP-treated clams exhibited significantly lower levels of AEC compared with LP treatments. A similar trend was shown by reburrowing behaviour; HP-treated clams reburrowed less. Laboratory results were less clear: a very low level of AEC was measured in both control and treated clams. These poor conditions in foot muscle did not indicate worsening at organism level, as no dead or dying clams were recorded throughout the experiment. However, repeated mechanical stress reduced the percentage of reburrowing clams, which suggested that harvesting may affect reburrowing behaviour.