Fish are a highly diverse group of aquatic vertebrates, most of which breathe through gills and move with fins. People encounter them as wildlife, aquarium pets, food, and catches from fisheries—but those contexts raise different questions. Here is a practical overview, with food-safety and sustainability claims kept within the evidence available for the species, place, and year involved.
What are fish?
Fish are aquatic vertebrates: animals with backbones adapted to life in water. Most have gills, fins, and scales, but fish vary widely in body shape, habitat, size, and behavior; not every species has the same features or needs. The word “fish” covers many different species, so a claim that applies to one fish cannot automatically be applied to all of them.
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Fish live in freshwater, saltwater, and habitats where conditions change between the two. Some are kept in home aquariums, while others are caught or raised for food. Those are different settings: a commercial fish farm is not the same thing as a home aquarium.
What do fish eat?
A fish’s diet depends on its species, life stage, and habitat. Depending on the fish, food may include algae or other plant matter, plankton, insects, crustaceans, worms, or smaller fish. Some species eat a varied diet; others specialize. There is no single food that is suitable for every fish, especially in an aquarium, where the correct diet depends on identifying the species and its care requirements.
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How do people obtain fish?
Wild capture
Wild-caught fish come from fisheries that capture fish living in natural waters. Their origin and management matter: sustainability is assessed for particular stocks and places, not for “wild fish” as one universal category.
Aquaculture
Aquaculture means farming organisms in water. NOAA defines it as “the breeding, rearing, and harvesting of fish, shellfish, algae, and other organisms in all types of water environments.” It includes freshwater and marine production; marine fish may be raised in net pens or land-based tanks, while U.S. freshwater examples include catfish and trout. NOAA Ocean Service explains aquaculture.
Aquaculture is a major source of food, but many reported totals include more than finfish. FDA says aquaculture supplies more than 50 percent of seafood produced for human consumption worldwide and that about 580 aquatic species are farmed. Its aquacultured-seafood page does not attach a reporting year to those figures, and “seafood” and “aquatic species” are broader categories than finfish alone. FDA’s aquacultured seafood guidance describes the scope and food-safety requirements.
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Recent production totals also need their scope stated. FAO estimated that global fisheries and aquaculture production reached 235 million tonnes in 2024, including 195 million tonnes of aquatic animals; aquaculture production of aquatic animals exceeded 100 million tonnes that year for the first time. These are aquatic-animal figures, not finfish-only totals. FAO’s 2026 SOFIA announcement reports the estimates.
Wild-caught or farm-raised: which should you choose?
Neither label alone establishes that a fish is safer or more sustainable. Compare the same species and market context where possible, then look at how it was produced, where it came from, the applicable safety controls, and stock or environmental information relevant to that source.
| Question | Wild-caught | Farm-raised |
|---|---|---|
| How it is produced | Captured from a natural fishery. | Raised in an aquatic production system; systems and species vary. |
| Food-safety standards in the United States | Subject to FDA food-safety standards and regulatory requirements. | Domestic and imported aquacultured seafood are held to the same FDA food-safety standards and regulatory requirements as wild-caught seafood. |
| What sustainability depends on | The particular fish stock, location, management, and catch level. | The species, production system, location, and environmental effects; the label alone does not settle the question. |
FDA identifies regulated animal-drug residues as one hazard it considers for aquaculture products. That is a food-safety control issue, not proof that farmed fish as a category is unsafe. In the United States, both farmed and wild-caught seafood are covered by FDA requirements. FDA’s guidance on aquacultured seafood discusses these requirements.
Is fish healthy to eat?
Seafood can be part of a healthy dietary pattern, but “fish” is not a single nutritional or safety category. Species differ, and advice can also depend on a person’s age and circumstances. In its summary of the U.S. 2020–2025 Dietary Guidelines, FDA advised women who might become pregnant, are pregnant, or are lactating, and young children, to eat two to three servings per week of seafood lower in mercury. Because that guideline period has ended, use FDA’s current, species-specific advice rather than treating the older summary as a current recommendation for every fish or person. FDA’s seafood guidance links food safety and consumption advice.
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For a particular meal, check the species against current FDA mercury advice, especially when choosing fish for someone in a group covered by specific guidance. A broad recommendation to “eat fish” is not a substitute for checking the species.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How can you identify a fish?
Start with where the fish was found or sold, then compare visible features such as body shape, fin placement, markings, and mouth shape with a reliable species reference. Common names can be ambiguous, and a fish’s appearance may change with age or between populations. For seafood, correct identification also matters because substitution can make a product’s label misleading.
The U.S. FDA’s Regulatory Fish Encyclopedia is a reference intended to help seafood purchasers and officials identify fish species and address substitution. It is useful for species-level reference, not a replacement for expert identification in cases where a mistaken identification could affect health or regulatory decisions. Open FDA’s Regulatory Fish Encyclopedia.
What do fishery status figures mean?
Fishery figures need a place, year, and measure. In NOAA Fisheries’ report on U.S.-managed stocks, 23 of 522 stocks or stock complexes were subject to overfishing and 42 were overfished at the end of 2024. These are separate findings for U.S.-managed stocks, not a global estimate and not a statement about every fish sold or caught.
- Subject to overfishing means the current fishing rate or pressure is too high.
- Overfished describes a stock’s condition—its population is below the relevant threshold.
A stock can be overfished without currently being subject to overfishing, or subject to overfishing without yet being overfished. NOAA’s status report explains the U.S. determinations and their scope: Status of Stocks 2024.
For additional U.S. context, NOAA Fisheries reports that marine and freshwater aquaculture produced 688 million pounds, valued at $1.3 billion, in 2023. Those figures describe U.S. aquaculture production for that year, not global output or seafood consumption. NOAA’s Fisheries of the United States page reports the figures.
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