Ecotoxicology and Food science. Can you help? please

A large dinner table of people celebrating a birthday in Far North Queensland are taken separately to hospital early the next morning complaining of nausea, headaches and convulsions. On investigation by the food authorities, the restaurant owner is told that what they ate at the restaurant was to blame. The restaurant owner vehemently insists that the coral trout and shellfish served to the diners was fresh, having just been caught that morning, the first time fishermen have been allowed by fisheries authorities to fish in estuaries and on the offshore reef for a fortnight after a violent storm and flooding.
 
A. Explain to the restaurant owner how and why the food he served caused the problem, including the organisms and toxins responsible but that he is not to blame.

B. If the diners sue, who should they sue? What could the body that they sue have done to prevent this?                   

C. Could they have tested the food, and if so, how? And why did they not do this routinely?