Our creator gave us easy ways to know what is food and what is not. Among things that live in fresh water or salt water the standard holds to fish having fins and scales. The reason things were established this way is because these are the fish that will not do our body harm. Eating sea food that is unclean will not only harm our body, but could cause lasting health problems.
Shellfish – Risky food
Generally speaking, unclean aquatic creatures are either scavengers or predatory carnivores (such as most sharks). Most clean, edible marine life—those with both fins and scales—are found in deep or fast-running waters and primarily consume algae. However, many varieties (such as the common bass) eat smaller fish, frogs, insects, etc. however, clean fish do not eat dead matter. They also have an efficient enzymatic system of detoxification.
Most of the unclean aquatic creatures are bottom feeders. These are scavengers that scour marine beds for dead, decaying matter. The highly popular catfish—which has fins but no scales—is a bottom feeding scavenger and not good to be eaten. This feature is precisely what makes unclean marine life unsafe to eat.
Shellfish are bivalve filter feeders, hence they rapidly accumulate toxins produced by microscopic algae such as dinoflagellates, diatoms, and cyanobacteria. The toxicity levels of marine bed algae are often seasonal: when the algae of a given area are in “bloom,” the toxicity is high; shellfish that feed on such algae become highly toxic.20 However, it is important to understand that these toxins are a normal byproduct of their existence. In other words, shellfish are always toxic, and have the potential to become dangerously toxic at any time. Attempting to predict the toxicity level of shellfish is highly problematic, sort of like playing Russian roulette!