Domoic acid in Portuguese shellfish and fish.

The presence of domoic acid (DA) in Portuguese shellfish is a recurrent event that affects shellfish resources several times a year, mainly in spring and autumn. Levels of domoic acid as high as twice the regulatory level of 20 microg DA/g tissue are not unusual. When several shellfish species are exploited in the same restricted area, common cockle (Cerastoderma edule) and carpet shell (Venerupis pullastra) are usually amongst the most toxic, followed by peppery furrow shell, clam, mussel, oyster and razor clam. In whole sardine, domoic acid was detected in levels exceeding sometimes the regulatory limit. Fortunately, toxicity is restricted to the gut content, and does not accumulate in muscle tissue. In brain tissue, domoic acid was detected in levels generally below 1 microg/g. Domoic acid was confirmed by spectra acquired with a diode-array detector. The most toxic samples were confirmed by mass spectrometry.