Bycatch in commercial fishing refers to the unintentional capture of non-target marine life, such as the wrong species, undersized fish, or vulnerable animals like sea turtles and marine mammals. This accidental catch is often discarded back into the ocean, frequently dead or dying, representing a massive waste of marine resources. The United Nations Food and Agriculture Organization estimates that around 9.1 million metric tons of catch are discarded annually across global fisheries. Reducing bycatch is a significant focus of marine conservation efforts to protect biodiversity and ensure the long-term sustainability of ocean ecosystems.
Inherently Selective Fishing Techniques
The commercial fishing techniques with the lowest rates of bycatch are those that rely on individual selection or species-specific targeting, making them inherently selective by design. These methods minimize the entanglement or capture of unintended animals because the gear interacts with the marine life on a smaller, more controlled scale.
Pole-and-Line and Handlining
Pole-and-line fishing and handlining are among the most selective techniques, often achieving bycatch rates of less than one percent. Fishermen catch fish one at a time using a single hook and line, which allows for the immediate identification of the catch. Any non-target species, undersized fish, or prohibited catch can be released instantly and safely back into the water, greatly increasing their chances of survival.
Traps and Pots
Traps and pots also demonstrate high selectivity because they rely on species-specific behavior to lure the target catch inside a contained structure. The design of these rigid devices can be engineered to reduce bycatch through the use of escape gaps or vents. These openings allow smaller, non-target individuals or juvenile fish to exit the trap before it is hauled to the surface, maintaining a healthy population structure.
Jigging
Jigging uses an artificial lure or baited hook rapidly moved through the water, appealing only to actively feeding fish. The active, one-on-one nature of this hook-and-line technique means the fisher is directly targeting the desired species and size. Unlike passive, large-scale netting, the gear does not indiscriminately sweep up marine life, resulting in a naturally low rate of unintended capture.
Gear Modification and Operational Adjustments
For fishing methods that are inherently less selective, such as trawling or longlining, technological solutions and changes in operation are applied to reduce bycatch rates significantly. These applied fixes seek to retrofit existing gear to allow non-target species to escape safely.
Trawl Net Modifications
Trawl nets are often modified with Turtle Excluder Devices (TEDs). These are grates built into the net that separate large animals, such as sea turtles, from the catch, guiding them out through an escape hatch while retaining the target species. Similarly, Fish Excluder Devices or square-mesh panels are inserted into the net body. These openings allow juvenile fish and other small non-target species to swim out safely.
Longline and Acoustic Adjustments
In longline fisheries, modifications focus on the hook and line itself. Using circle hooks instead of J-shaped hooks reduces the bycatch of vulnerable species like sea turtles and seabirds, as the hook shape is less likely to be swallowed. Acoustic deterrents, sometimes called “pingers,” are attached to nets to emit sounds that repel marine mammals, preventing their entanglement.
Operational Adjustments
Operational adjustments are used to avoid vulnerable species without changing the gear structure. These include changing the setting depth of lines, fishing only at certain times of day, or avoiding aggregation points or migratory routes for non-target species. For instance, adding brightly colored streamer lines above the water near longlines deters seabirds from diving for the bait, significantly reducing seabird deaths.
Economic and Ecological Trade-Offs
Despite the existence of highly selective fishing methods, they are not universally adopted across the industry due to practical constraints involving economic and ecological trade-offs. Inherently selective techniques, such as pole-and-line fishing, are labor-intensive, requiring more personnel and time to land a comparable amount of fish. This increased labor raises operational costs, resulting in a higher price point for the product. These highly selective methods also operate on a much smaller scale and cannot meet the immense volume demanded by global commodity markets. Industrial fishing operations often require the high-volume yields of less selective gear like large purse seines or trawls, meaning the economic pressure to maximize catch per unit of effort often outweighs the incentive to minimize bycatch.
Market Incentives
A growing consumer preference for sustainably sourced seafood has begun to offset some of these economic trade-offs. The demand for fish certified as “pole-and-line caught” or “sustainably trapped” creates a market premium that helps absorb the higher production costs of low-bycatch methods. This market-driven demand provides an economic incentive for fishers to transition to more selective gear, balancing ecological protection with financial viability.