How new fishing tech can reduce bycatch of turtles and other creatures

Background

Bycatch—the unintentional capture of non-target species—has long been a stubborn problem in industrial and small-scale fisheries alike. Sea turtles, dolphins and porpoises, sharks and rays, seabirds, and juvenile fish are all vulnerable. These encounters are often fatal, and they carry ecological costs (removing slow-to-reproduce species), legal and reputational risks (endangered species protections, market access), and real economic penalties (lost time sorting nets, damaged gear, and fines). Estimates vary by region and fishery, but global assessments in the past decade suggest roughly one in ten fish brought to port is unintended catch, with some high-risk fisheries far above that average.

The good news: a new generation of gear, sensors, and decision tools is escaping the realm of pilot projects and showing real, repeatable reductions in bycatch—often without cutting target catch. Better yet, many of these devices retrofit to existing nets or lines, cost hundreds (not tens of thousands) of dollars, and can be tuned to the behavior and size of specific species.

Historically, several innovations blazed the trail:

• Turtle Excluder Devices (TEDs): Rigid or semi-rigid grates in shrimp trawls that shunt large animals, including sea turtles, toward an escape flap while shrimp pass through. Versions of TEDs have been required in many shrimp trawl fisheries since the 1990s, and later designs improved flow to reduce shrimp loss.
• Bycatch Reduction Devices (BRDs): A broader category that includes escape panels, square-mesh windows, and codend modifications that let smaller or non-target species slip out.
• Circle hooks and bait changes in longline fisheries: Swapping J-hooks and squid bait for circle hooks and fish bait has repeatedly reduced turtle bycatch without collapsing catch rates for tunas and swordfish.

What’s different now is a surge of practical, science-guided tweaks—especially for nets—that combine light, sound, geometry, and even machine vision to help non-target animals avoid capture.

What happened

Recent field trials and comparative studies across multiple oceans show strong, sometimes striking reductions in bycatch when nets are equipped with inexpensive electronics or simple mechanical guides. The throughline: these tools lean on species’ sensory cues and swimming behavior.

• LED-lit gillnets and trawls: Attaching cheap, durable LED modules along the float line or a panel of a net appears to make nets more visible to air-breathing vertebrates like sea turtles and marine mammals, and in some cases to seabirds. In several independent experiments in the eastern Pacific and Mediterranean small-scale gillnet fisheries, adding green or ultraviolet LEDs spaced along nets cut turtle entanglements by large fractions—from roughly half to well over two-thirds—while leaving fish catches statistically unchanged or only slightly reduced. A parallel approach in trawl nets uses internal lighting to illuminate escape openings and square-mesh panels so larger non-target animals can find them quickly.

• Refined excluder grids: Modern TEDs and Nordmøre-style grids (originally developed in Nordic shrimp fisheries) are tuned to the hydrodynamics of the trawl mouth and tailored to the size, flexibility, and behavior of local species. For example, steeper grid angles and larger bar spacing can let flatfish or crustaceans flow aft while guiding bulkier turtles or sharks to a top or bottom hatch. Trials of updated grids have reported substantial turtle and elasmobranch reductions with minimal loss of target catch, provided the grid angle and mesh transitions don’t create turbulence that deflects target species away.

• Acoustic pingers and reflective panels: Gillnets set for groundfish and monkfish have been notorious for incidental porpoise and dolphin entanglement. Small battery-powered “pingers” that emit periodic tones in ranges detectable to toothed whales have, in multiple fleets, lowered cetacean bycatch without measurable drops in the intended fish—though maintaining device spacing and batteries is critical. Experiments with high-contrast or reflective net panels can also improve detectability to echolocating animals.

• Smart escape hatches powered by cameras/AI: A handful of prototypes mount low-light cameras at the trawl mouth or in escape panels. When the onboard classifier recognizes a turtle silhouette or a protected shark, it triggers a servo to open a hatch or shifts a flow-directing flap. In the earliest sea trials, these systems have demonstrated accurate detections and on-demand release without crew intervention, though regulatory approval and ruggedization remain works in progress.

• Behaviorally selective tweaks: Seemingly small changes—towing speed, net depth, headline height, timing relative to dawn/dusk—can translate into major bycatch differences. Emerging decision-support apps combine satellite data (sea surface temperature, chlorophyll, fronts) with historical bycatch “hotspots” to nudge skippers toward lower-risk sets.

Together, these technologies form a ladder: from ultra-simple (clip-on lights) to sophisticated (AI-triggered hatches). Importantly, many of the most effective options are also the cheapest and easiest to maintain—one reason adoption is moving faster in small-scale fleets than it did for earlier, bulkier hardware.

Why nets with lights and grates work

• Vision and contrast: Sea turtles and many seabirds rely on visual cues. A gillnet is practically invisible underwater; adding LEDs or high-contrast panels makes it detectable in time to avoid. Some wavelengths (e.g., green or UV) appear particularly effective for turtles.
• Size-based sorting: Rigid or semi-rigid grids exploit simple geometry: shrimp, small fish, and krill slip between bars; larger animals cannot and are funneled out. The key is maintaining laminar flow to avoid pushing target animals toward the escape route.
• Sound as a warning: Odontocetes (toothed whales) can detect pinger tones from tens of meters away, cueing avoidance. The catch is habituation risk; rotating frequencies and ensuring appropriate spacing help.

What this means for turtles and “the rest of the net”

Turtles are emblematic because they’re air-breathers and many populations are threatened. But the same modifications that help turtles can also reduce:

• Small cetaceans in gillnets (with pingers and reflective panels)
• Sharks and rays in trawls and longlines (with excluders, magnetic or electric deterrents on hooks)
• Seabirds on longlines (with weighted lines, night setting, and bird-scaring streamers)

A persistent worry among fishers is that anything which helps turtles escape will also let valuable catch slip away. The strongest trials address this head-on by measuring target catch alongside bycatch. While no single device is universal, a pattern emerges: properly tuned lights and grids cut bycatch a lot and target catch a little—or not at all. In some cases, they can even boost efficiency by reducing time spent sorting and untangling.

The economics

• Direct costs: LED modules and pingers typically cost tens to a few hundred dollars per unit, with service lives spanning months to seasons; excluder grids are more expensive but long-lived.
• Savings: Less time hauling and sorting, lower gear damage, fewer regulatory penalties or closures, and improved access to eco-labels and premium markets.
• Fuel: Some grid designs actually reduce drag relative to unmodified nets, modestly trimming fuel burn per tow; poorly tuned ones do the opposite, which is why flow testing matters.

Limitations and caveats

• Fishery specificity: What works in a shallow, small-mesh gillnet fishery may not translate to deep pelagic trawls. Device spacing, wavelengths, and grid angles need local tuning.
• Maintenance: Lights and pingers are only effective when powered and properly spaced; lost or dead units can lull crews into a false sense of security.
• Non-target effects: Bright lights may change behavior of some target species or attract others; pingers can add to underwater noise. So far, the balance in many trials favors their use, but monitoring is prudent.
• Enforcement and verification: Regulators and buyers will want proof of use and performance. That’s driving growth in low-cost electronic monitoring (EM) and tamper-evident sensors.
• Edge cases: Very turbid water, extreme depths, or night/day transitions can complicate visual cues. AI-triggered escape systems need robust fail-safes to avoid accidental release of target catch or missed detections.

Key takeaways

• Bycatch is solvable enough to matter: Practical retrofits—especially LEDs on nets and refined excluder grids—have repeatedly slashed turtle and other wildlife bycatch in real fisheries.
• Selectivity doesn’t have to mean lost revenue: Many devices preserve target catch while reducing sorting time and gear damage, improving net margins.
• The best tech is often the simplest: Clip-on lights and well-angled grids frequently outperform complex solutions on cost-effectiveness and adoption.
• Data and design go hand in hand: Flow tanks, onboard cameras, and EM are closing the loop between design tweaks and at-sea results, speeding iteration.
• Policy can accelerate uptake: Where regulators clarify approved devices and buyers reward verified use, adoption jumps.

What to watch next

• Standardization and certification: Expect agencies to publish device specs (e.g., LED color, spacing, grid angles) that qualify for compliance or eco-label credits.
• Battery-free or energy-harvesting lights: Inductive-charged or flow-powered LEDs could remove a major maintenance headache.
• Smarter selectivity: More sea trials of camera-in-net classifiers triggering on-demand openings, with safeguards and transparent performance metrics.
• Dynamic ocean management: Apps that integrate satellite environmental data with real-time bycatch reports to steer effort away from hotspots.
• Small-scale fleet support: Microgrants, cooperative gear libraries, and training so village-scale fisheries can adopt lights, pingers, and grids.
• Ropeless trap gear: In fixed-gear fisheries, acoustic-release buoy lines promise fewer whale entanglements; scaling these systems at reasonable cost is a near-term frontier.

FAQ

• What is bycatch, exactly?
  Bycatch is the unintentional capture of species that fishers aren’t trying to catch—anything from turtles, dolphins, and seabirds to juvenile fish and invertebrates.

• Do these devices eliminate bycatch?
  No single device eliminates bycatch. But combinations—like LEDs plus escape panels in nets, or circle hooks plus bird-scaring lines in longlines—can reduce it dramatically, often by half or more in published trials.

• Won’t lights scare away the fish I want?
  It depends on the species and fishery. Many target species are less sensitive to the wavelengths and placements used, and trials often show little to no reduction in target catch. Local testing and tuning are key.

• Are pingers bad for marine mammals because of the added noise?
  Pingers add sound, but at low levels and intermittent patterns intended as warnings. Properly deployed, they’ve reduced entanglements for some species. Rotating frequencies and avoiding overuse help reduce habituation.

• How do Turtle Excluder Devices work in trawls?
  A grid sits inside the net at an angle. Small animals pass through the bars into the codend. Larger animals—like turtles—are guided to an escape flap. Getting the angle and flow right is crucial so shrimp or fish aren’t lost.

• What about small-scale fishers—can they afford this?
  Many LEDs and pingers are designed for artisanal nets and cost relatively little. Programs that provide gear at cost or via grants are expanding, and the time saved from fewer entanglements often pays for the devices quickly.

• How can I tell if my seafood came from a low-bycatch fishery?
  Look for certifications that include bycatch standards, ask retailers about gear types (e.g., pole-and-line tuna, trap-caught crustaceans with verified mitigation), and watch for traceability labels tied to electronic monitoring.

• Will this make seafood more expensive?
  Some gear has upfront costs, but lower sorting time, fewer fines, and stronger market access often offset them. Over time, widespread adoption can stabilize or even reduce costs by improving efficiency.

Source & original reading

Original article: https://arstechnica.com/science/2026/03/how-new-fishing-tech-can-reduce-bycatch-of-turtles-and-other-creatures/