Preventing bycatch requires a combination of smarter fishing gear, real-time ocean data, and technology that helps non-target species avoid nets and hooks in the first place. Global marine fisheries discard an estimated 9.1 million tonnes of unwanted catch each year, but proven solutions already exist that can cut bycatch dramatically for specific species.
Gear Modifications That Exclude Non-Target Species
The most direct way to reduce bycatch is to physically redesign fishing gear so that unwanted animals can escape. In shrimp trawling, two types of devices work together to protect different species. Turtle excluder devices (TEDs) are metal grids fitted inside the neck of a trawl net. When a sea turtle enters the net, the grid redirects it toward an opening at the top or bottom, letting it swim free. Current TED designs are 97 percent effective at excluding turtles from shrimp trawls.
Bycatch reduction devices (BRDs) tackle a different problem: the finfish that get swept up alongside shrimp. These include designs like the Fisheye, the Jones Davis, and composite panels, each engineered to create escape routes that fish will find and use while shrimp continue deeper into the net. In the Gulf of Mexico and South Atlantic, shrimp trawlers are required to use certified BRDs alongside TEDs, creating a layered defense that protects both reptiles and fish.
Acoustic Deterrents for Marine Mammals
Small cetaceans like harbor porpoises are particularly vulnerable to gillnets, which are nearly invisible underwater. Acoustic pingers, small battery-powered devices attached at intervals along a net, emit sounds that alert porpoises to the net’s presence before they become entangled. A landmark 1994 study found that pingers reduced harbor porpoise bycatch in sink gillnets by 92 percent.
The approach does have limitations. Questions remain about whether animals habituate to the sound over time, reducing its effectiveness. There’s also concern that pingers could displace marine mammals from important feeding habitat rather than simply steering them around the net. Still, for fisheries where porpoise bycatch is a serious problem, pingers remain one of the most effective single interventions available.
Protecting Seabirds on Longlines
Longline fishing, where thousands of baited hooks trail behind a vessel, poses a major threat to albatrosses, petrels, and other seabirds that dive for the bait as it enters the water. Tori lines (also called bird-scaring lines) are one of the simplest and most effective countermeasures. A tori line is towed from a high point at the back of the vessel, with brightly colored streamers dangling from it. These streamers scare birds away from the critical zone where baited hooks are still sinking and accessible.
Research on pelagic longline fleets found that tori lines reduced seabird bycatch from 0.85 birds per 1,000 hooks to just 0.13 birds per 1,000 hooks, roughly an 85 percent reduction. When the tori line stayed intact without tangles or breaks, the rate dropped even further to 0.07 birds per 1,000 hooks. The key variables are the height of the attachment point (around 6 meters above sea level works well) and keeping the streamers in good condition throughout the set.
Other seabird measures include weighting longlines so hooks sink faster, setting lines at night when most seabirds aren’t foraging, and dyeing bait to make it less visible from the air. Most effective programs combine several of these tactics.
LED Lights on Gillnets
One of the more promising newer approaches involves attaching green LED lights directly to gillnets. Controlled experiments off Mexico’s Baja California peninsula showed that illuminated gillnets reduced total discarded bycatch by 63 percent. The results were especially striking for certain groups: bycatch of sharks, skates, and rays dropped by 95 percent, Humboldt squid bycatch fell by 81 percent, and unwanted finfish decreased by 48 percent. Critically, the lights did not reduce the catch of target fish species or lower their market value, meaning fishers didn’t lose income.
Illuminated nets also show promise for sea turtles, which can see the lights and avoid the net entirely. Because LEDs are inexpensive and solar-rechargeable versions are becoming available, this approach could scale to small-scale fisheries in developing countries where bycatch monitoring is minimal.
Dynamic Ocean Management
Static fishing closures, where a fixed area is off-limits year-round, protect habitat but can shut fishers out of productive grounds even when the species of concern has moved elsewhere. Dynamic ocean management uses daily satellite data to track ocean conditions like temperature fronts and chlorophyll concentrations, then predicts where protected species are likely to be on any given day.
NOAA researchers have developed tools that integrate species-specific probability maps into a single predictive surface, weighting each species by its conservation priority. The result is temporary, targeted closures that shift with the animals. Studies have found that dynamic closures can be 2 to 10 times smaller than static closures while still providing equivalent protection for endangered non-target species. That means less lost fishing opportunity and better compliance, since fishers are more likely to respect rules that feel proportionate.
Electronic Monitoring and AI
Accurate bycatch data is the foundation of every prevention strategy, and one of the biggest obstacles has been getting reliable information from vessels at sea. Traditional observer programs cover only a fraction of fishing trips. Electronic monitoring systems, which combine onboard cameras, GPS, and sensors, can record fishing activity continuously and independently.
These systems verify whether vessels are following catch limits, using required mitigation gear like TEDs or tori lines, and accurately reporting what they catch. The newest generation uses machine learning to automatically analyze video footage, identifying species in the catch without a human reviewer watching every hour of tape. Solar-powered camera systems are also expanding EM into longline fleets operating far offshore, where placing human observers is expensive and logistically difficult.
Regulatory Frameworks That Drive Change
Technology alone doesn’t reduce bycatch without regulations that require its use. In the United States, the Marine Mammal Protection Act establishes a “potential biological removal” level for every marine mammal population: the maximum number of animals that can be killed by human activity while still allowing the population to recover. When a stock’s bycatch exceeds that threshold, it’s classified as a strategic stock, triggering a take reduction plan that must bring mortality below the limit within six months.
This framework creates a direct link between population science and fishing rules. Take reduction teams, which include fishers, scientists, and conservation groups, negotiate specific gear requirements and area restrictions tailored to the fishery causing the problem. Similar regulatory triggers exist internationally through regional fisheries management organizations, which set bycatch limits and require mitigation measures for tuna longline and purse seine fleets.
What Individual Fishers Can Do
If you fish commercially or recreationally, the most impactful steps are choosing the right gear for your target species and staying informed about where protected species concentrate. Using circle hooks instead of J-hooks on longlines reduces gut-hooking of sea turtles. Switching to larger mesh sizes lets juvenile fish escape. Setting nets during times when non-target species are less active, such as deploying longlines at night to avoid seabirds, costs nothing and can cut bycatch substantially.
Participating in real-time reporting networks, where fishers share information about bycatch encounters so others can avoid hotspots, turns individual observations into collective protection. Several fisheries now run voluntary programs where skippers receive daily maps showing areas to avoid, keeping them on productive grounds while steering clear of protected species aggregations.