Experts Warn About Eating Fish After Seeing What Was Found Inside — But What Does It Really Mean?

A shocking image circulating online shows a market filled with fish, including one large fish with what appears to be a mouth full of small stones or gravel. The dramatic caption claims that experts are warning people to stop eating a particular fish after seeing what was found inside.

The image is certainly unsettling.

But before throwing fish out of your diet, there is an important point to understand: a photograph alone cannot establish that the fish shown is contaminated, poisonous, or unsafe to eat. The image also does not provide enough information to identify the fish species, where it came from, or whether the material in its mouth is actually a health hazard.

What we do know is that fish can contain a variety of natural materials depending on the species, habitat, and feeding behavior.

Here is what consumers should actually know.

What Could Be Inside a Fish's Mouth?

Some fish naturally feed from the bottom of rivers, lakes, ponds, or coastal environments.

When feeding, they may accidentally ingest:

• Small stones
• Sand
• Gravel
• Shell fragments
• Plant material
• Mud
• Small aquatic organisms

Finding small pieces of sediment or other material inside a fish does not automatically mean that the fish is poisonous or contaminated.

Some fish use specialized mouth structures to search through sediment for food. Bottom-feeding species may therefore encounter considerably more sand and small particles than fish that primarily feed in open water.

The digestive tract can also contain material from the animal's last meal.

So a strange-looking substance inside a fish isn't necessarily evidence of a dangerous toxin.

Does Finding Gravel Mean the Fish Is Unsafe?

Not necessarily.

If a fish has accidentally swallowed small stones or sediment, that material is generally a physical contaminant, not automatically a chemical poison.

During normal fish preparation, the digestive organs are removed, and the fish is cleaned before cooking.

The bigger food-safety concerns are usually things such as:

Bacterial contamination

Parasites

Environmental pollutants

Naturally occurring toxins in certain species

Improper storage or handling

Insufficient cooking

These risks are much more important than the mere presence of a few small stones.

The Real Danger: Raw or Undercooked Fish

One of the most important food-safety issues involving fish is inadequate cooking.

Raw or undercooked fish can contain parasites or disease-causing microorganisms.

Depending on the species and preparation method, consuming raw fish can expose a person to parasites such as Anisakis and to certain bacterial pathogens.

This is why fish intended to be eaten raw requires appropriate sourcing and handling.

Simply putting questionable raw fish into a home freezer or washing it under running water should not be assumed to eliminate every possible hazard.

For ordinary cooked fish, thorough cooking is one of the most important safety measures.

Some Fish Can Accumulate Mercury

Another legitimate concern has nothing to do with stones.

Certain fish contain higher concentrations of methylmercury, a contaminant that can accumulate through the aquatic food chain.

Large, long-lived predatory fish tend to accumulate more mercury than smaller fish.

Examples of fish that can contain relatively high mercury levels include certain types of: