In general, larvae and juveniles are more vulnerable to injury or death from exposure to these substances. Studies of the effects of toxic compounds must consider both the age and species of the specimens to fully assess the chemical's toxicity. Bacteria Shellfish collect fecal bacteria in their gut, making them good indicators of recent exposure to sewage waste. Since fecal coliform often indicate the presence of human or animal pathogens, tainted shellfish serve as a warning and signal that an area may not be suitable for recreation or fishing. Unlike water sampling for bacterial contamination, shellfish tissue analysis acts as a market testthat is, it determines whether the shellfish are fit for human consump tion.
Officials can set predetermined levels of fecal coliform in shellfish as a management standard.
Areas where levels exceed this standard should be closed to commercial and recreational shellfish collection until the problem is resolved. Paralytic Shellfish Poisoning Paralytic shellfish poisoning is caused by several species of dinoflagellatespredominantly marine, microscopic, one-celled organisms. Although most species are harmless, the types responsible for PSP secrete a neurotoxin. When shellfish such as clams, oysters, mussels, and scallops ingest these dinoflagellates, the neurotoxin accumulates in their tissue. Although the animals are unaffected by the toxin, humans eating these shellfish can experience serious reactions.