The fish on your plate has a story. Where it was caught, how it was caught, and whether its population is healthy or collapsing — these details matter not just for the ocean but for the future of seafood itself. Overfishing is one of the most significant threats to marine ecosystems, yet it's also one of the most solvable. Understanding which fish to eat and which to avoid is a powerful way individuals can contribute to ocean health.

What Is Overfishing?

Overfishing occurs when fish are caught at a rate faster than they can reproduce. When fishing pressure exceeds the reproductive capacity of a population, the population declines. If left unchecked, this can lead to commercial extinction — the point where catching the species is no longer economically viable — or actual extinction.

The scale of the problem is sobering. According to the UN Food and Agriculture Organization (FAO), approximately 35% of global fish stocks are overfished — up from 10% in 1974. Another 57% are fished at maximum sustainable yield, meaning they cannot sustain additional fishing pressure. Only about 8% of fish stocks are underfished.

By the Numbers

Global per capita fish consumption has more than doubled since 1960, reaching approximately 20.5 kg per person per year. Fish provide about 3.3 billion people with almost 20% of their average per capita intake of animal protein. The demand is enormous — and growing.

The Environmental Impact

Ecosystem Collapse

Removing too many fish from an ecosystem disrupts food webs. When top predators like tuna, sharks, and swordfish are overfished, their prey species can proliferate, creating imbalances that cascade through the entire ecosystem. When herbivorous fish are overfished, algae can overgrow and smother coral reefs.

Bycatch

Bycatch — the incidental capture of non-target species — is a massive problem. An estimated 9.1 million tons of marine life are discarded as bycatch annually. This includes:

  • Sea turtles, dolphins, and whales caught in nets and on longlines
  • Non-target fish species that are discarded (often dead)
  • Sharks, many species of which are already threatened
  • Seabirds caught on longline hooks

Habitat Damage

Some fishing methods cause severe habitat damage. Bottom trawling — dragging heavy nets across the seafloor — destroys coral reefs, sponge gardens, and other seafloor habitats that can take decades or centuries to recover. Dynamite and cyanide fishing, though illegal in most countries, continue to destroy reefs in parts of Southeast Asia and Africa.

Ghost Fishing

Lost or abandoned fishing gear (ghost gear) continues to catch fish, turtles, and marine mammals for years. An estimated 640,000 tons of fishing gear are lost or abandoned annually, making it one of the most harmful forms of marine debris.

Fishing Methods: What to Know

How fish are caught matters as much as which fish are caught:

  • Pole and line: One fish at a time, minimal bycatch. Most sustainable method for tuna and other large fish.
  • Troll fishing: Lines towed behind a boat. Low bycatch, minimal habitat impact.
  • Purse seine with FADs (Fish Aggregating Devices): Large nets that can have high bycatch of juvenile fish and bycatch species. FAD-free purse seine is better.
  • Longlining: Miles of line with thousands of hooks. Can have significant bycatch of turtles, sharks, and seabirds unless mitigation measures are used.
  • Bottom trawling: Heavy nets dragged on the seafloor. High bycatch and severe habitat damage. Among the most destructive methods.
  • Gillnetting: Walls of netting that can entangle marine mammals and turtles.

Which Fish to Eat and Which to Avoid

Choosing sustainable seafood is one of the most effective individual actions for ocean conservation. Here's a practical guide:

Generally Sustainable Choices

  • Farmed bivalves (mussels, oysters, clams): Filter feeders that improve water quality, require no feed inputs, and have minimal environmental impact.
  • Sardines and anchovies: Small, fast-reproducing fish low on the food chain. Often certified sustainable.
  • Pole-caught tuna: Particularly skipjack tuna caught by pole and line. Look for "pole and line caught" labels.
  • Farmed rainbow trout (inland): Well-managed inland operations have low environmental impact.
  • Alaska wild salmon: Well-managed fisheries with strong population monitoring. Look for MSC certification.
  • Mackerel (Atlantic): Fast-reproducing, well-managed populations (check regional status).

Fish to Avoid or Limit

  • Bluefin tuna: Severely overfished, all three species (Atlantic, Pacific, Southern) are threatened or endangered.
  • Shark: Slow-growing, late-maturing species that cannot sustain fishing pressure. Many species are endangered.
  • Orange roughy: Extremely slow-growing (can live over 100 years), deep-sea species particularly vulnerable to overfishing.
  • Chilean sea bass (Patagonian toothfish): Often caught illegally, slow-growing, and frequently associated with bycatch of seabirds.
  • Farmed salmon (conventional): High feed requirements (wild fish used as feed), potential for pollution and disease transfer to wild populations.
  • Atlantic cod (some populations): Some stocks have collapsed historically and have not fully recovered.
  • Swordfish: Often high in mercury and some populations are overfished.

The Mercury Factor

Beyond sustainability, mercury contamination affects which fish are safe to eat. Large, long-lived predatory fish (tuna, swordfish, shark, marlin) accumulate mercury through biomagnification. Pregnant women, nursing mothers, and young children should limit consumption of these species. Smaller, shorter-lived fish (sardines, salmon, trout) generally have lower mercury levels.

Certification Labels to Look For

Several certification programs help consumers identify sustainable seafood:

  • Marine Stewardship Council (MSC): Blue tick label for wild-caught seafood from certified sustainable fisheries. The most widely recognized certification.
  • Aquaculture Stewardship Council (ASC): Certification for responsibly farmed seafood.
  • Friend of the Sea: Certifies both wild-caught and farmed seafood from sustainable sources.
  • Best Aquaculture Practices (BAP): Certification covering environmental and social responsibility in aquaculture.

While no certification is perfect, looking for these labels is a significant improvement over buying without any information.

The Role of Aquaculture

Fish farming (aquaculture) now provides more than half of all seafood consumed globally. Done well, aquaculture can be sustainable and reduce pressure on wild stocks. Done poorly, it can cause pollution, spread disease to wild populations, and require more wild fish as feed than it produces.

Sustainable aquaculture examples include:

  • Bivalve farming (mussels, oysters, clams) — no feed needed, filters water
  • Seaweed farming — no feed needed, absorbs nutrients, provides habitat
  • Inland recirculating systems — closed systems that minimize environmental impact
  • Integrated multi-trophic aquaculture — combining species that benefit each other

Problematic aquaculture includes conventional open-net salmon farming (pollution, disease, escape) and shrimp farming in some regions (mangrove destruction).

What You Can Do

  1. Check before you buy: Use apps like the Monterey Bay Aquarium Seafood Watch or the MSC's "Good Fish Guide" to check sustainability ratings.
  2. Look for certifications: Choose MSC, ASC, or other certified products when available.
  3. Ask questions: At restaurants and fish markets, ask where the fish came from and how it was caught.
  4. Diversify your choices: Trying less-common, sustainable species reduces pressure on overfished favorites.
  5. Eat lower on the food chain: Small fish like sardines and anchovies are more sustainable than large predators.
  6. Support policy: Advocate for science-based fisheries management, marine protected areas, and ending harmful subsidies.
  7. Reduce waste: Approximately 35% of caught fish is wasted. Buy what you need and use it fully.

The Path Forward

The good news is that overfishing is solvable. When fisheries are managed sustainably — with science-based catch limits, protected areas, and effective enforcement — fish populations recover. Examples include the recovery of US fisheries under the Magnuson-Stevens Act, where 47 once-overfished stocks have been rebuilt since 2000.

The challenge is global. International waters, IUU (illegal, unreported, and unregulated) fishing, and subsidies that incentivize overcapacity all undermine sustainable management. But consumer demand for sustainable seafood is one of the most powerful forces for change. When markets reward sustainable fishing, the fishing industry adapts.

Every Meal Matters

Your seafood choices are votes for the kind of ocean you want. Every time you choose a sustainable option over an unsustainable one, you send a signal to the market. You support well-managed fisheries and deny revenue to destructive practices. Multiply that by millions of consumers, and you have the power to transform an industry.

The ocean has fed humanity for as long as we've existed. By choosing seafood wisely, we can ensure it continues to feed us — and future generations — for centuries to come. It starts with knowing what's on your plate.

Learn more about ocean conservation in our guide to how individual actions affect ocean health.