Overfishing happens when more fish are harvested than is environmentally sustainable. Simply put, it means we’re pulling fish out of the water faster than they can reproduce.

Most of the fish we consume are predators. When their populations decline or disappear, prey species’ populations go unchecked and can grow out of proportion. Ultimately, overfishing alters the food web and changes how certain ecosystems function, which can have a devastating impact on biodiversity and the health and productivity of the ocean.

Without giving overfished species opportunities to reproduce and recover their populations, humanity is placing sustained pressure on many species and fishing them to the brink of extinction.

The destructive process of overfishing has been documented as far back as 1,000 years ago when Europeans exploited local freshwater fisheries until they collapsed, which meant they started relying more on coastal fisheries.

Since then, fishing technology has evolved to the point where we can target species everywhere they swim rather than focusing on the migration patterns that bring them within reach.

Once coastal fisheries were wiped out, offshore fisheries became the new target. Now, as those fisheries become depleted, the industry is starting to fish even deeper using the same wasteful and indiscriminate practices like bottom trawling, dredging, longlining, and drift netting that are destroying offshore fisheries.

Bycatch is the unintentional harvest of non-target species like dolphins, sea turtles, whales, and protected fish caused by nonselective fishing gear and tactics.

Bycatch can contribute to overfishing and slow efforts to rebuild fish stocks. It contributes to population declines and slow population recovery for vulnerable and endangered species.

Many types of fishing result in bycatch, including long line fishing, drift nets, gillnets, and purse seine nets, but activities like trawling, which involves dragging a trawl net across the sea floor, can be especially harmful; up to 90% of a trawl net’s total catch can be bycatch.

Lost and abandoned fishing gear like nets, traps, pots, ropes, and buoys account for about 10% of all marine debris. Once lost, derelict fishing gear becomes a significant entanglement risk that can continue to capture and kill both target and non-target species, which contributes to both overfishing and bycatch.

However, not all marine debris is distributed evenly across the ocean. A recent sample taken from the surface of the Great Pacific Garbage Patch found that fishing nets accounted for 46% of all the plastic recovered, with other types of fishing gear like ropes, oyster spacers, eel traps, crates, and baskets accounting for the majority of the other debris recovered.

Some fishing practices destroy habitats that provide food and shelter to a variety of marine species and can be permanently damaging to the marine ecosystem.

Dredging, like trawling, involves dragging equipment across the sea floor which can cause sediment to become suspended in the water column and decrease water quality, biomass, and the production of benthic species.

Blast fishing uses sticks of dynamite to cause explosions that stun nearby fish and cause them to float to the surface for easy harvesting. However, this type of fishing also destroys coral reefs, oyster beds, and other productive habitats and can impact many species and conservation efforts.

Many fish farms are set up in an “open system,” or an enclosed area of the ocean, where infectious diseases from pathogens such as bacteria, viruses, and parasites can easily spread from cultured fish to native fish. Vibrio, Aemonas, and Renibacterium are some of the most common bacterial infections. Common viruses include Birnaviridae, Rhabdoviridae, and Iridoviridae.

Open systems also create conditions where non-native or genetically modified species enter the environment and threaten or reproduce with the native species, which can upset the local ecosystem and impact fish populations in the surrounding waters.

Some of our favorite seafoods are also top ocean predators like tuna and salmon. These are large, carnivorous fish that require high-fat diets. Many prey species face pressure from overfishing that stems from the effort to feed and sustain these fish when farmed. Some farms use “fish meal” as an alternative; however, this combination of fish oil, wheat products, and chemicals isn’t easily digested by fish who aren’t designed to metabolize carbs. Since fish oils are used, even “fish meal” can contribute to overfishing.

Densely-packed fish farms not only facilitate the spread of infectious diseases, they also create waste that gets discharged into local ecosystems where it can contaminate the surrounding environment. This is a concern even for solid, closed-wall, and fully-contained aquaculture systems.

While “closed systems” may be a better alternative to existing aquaculture methods, there are barriers to implementing them successfully on a commercial scale. The high energy costs associated with the systems’ water pumps and the cost of electricity to keep them running can be barriers to operating them at a commercial scale.

Seafood Watch is a program run by the Monterey Bay Aquarium that helps consumers and businesses choose sustainable seafood with detailed information on how products are fished or farmed.

NOAA’s FishWatch helps consumers understand science, laws, and management in order to make informed seafood choices.

On pre-packaged foods, you can look for the labels from the Marine Stewardship Council, which sets standards for sustainable wild-caught fish and certifies fisheries that meets those standards, and the Aquaculture Stewardship Council, which does the same for fish farms.

Just remember that certification doesn’t necessarily mean your seafood is audited on a regular basis. Always do your own research to understand how these or any certifications are achieved and maintained.

The more people that become aware of issues in the commercial fishing industry, the more we can do to drive positive change. Talk to your friends. Talk to your family. Contact your favorite restaurants and grocery stores about the products they sell. Reach out to your local representatives and demand action. Remember, we’re all in this together.