Long Line: Procedure, Benefits, Risks, Recovery and Alternatives

Long line techniques span fisheries, aquaculture, and conservation. Whether you're an environmentalist, a seafood enthusiast, or a fishery professional, understanding how long line methods work—and their broader impacts—can help you appreciate efforts towards more sustainable and effective aquatic resource management. This article walks you through every aspect of long line use: from how procedures are performed, to the benefits, risks, aftercare, and what alternatives exist.

Long Line: The Procedure

Long line methods are versatile, used for both fishing (commercial and research) and aquaculture (such as mussel farming). The central idea is simple: a main line, often hundreds to thousands of meters long, is set horizontally in the water and equipped with numerous branch lines (called snoods) that carry hooks or culture substrates. The procedure varies according to target species, environment, and objectives.

Application	Approach	Key Steps	Sources
Fishing	Baited hooks	Mainline, branch lines, bait	1 5 6 9
Aquaculture	Substrate lines	Suspended ropes, spat capture	2 4
Conservation	Bycatch mitigation	Weighted lines, night setting	1 3 6 9

Table 1: Long Line Procedure Types and Approaches

Fishing Applications

In fisheries, long lines are deployed from a boat, either at the bottom (demersal), in midwater (pelagic), or near the surface. Branch lines with baited hooks are spaced at intervals, and the line is left to "soak" for several hours, attracting target fish such as cod, ling, catfish, or even apex predators like European catfish 5 6. Variations exist for different species, including hook spacing, bait type, and sink rates.

Aquaculture Applications

Long lines are also central to shellfish aquaculture—especially mussel and oyster farming. Here, ropes or mesh socks are suspended from the main line, providing a substrate for mussel larvae (spat) to settle and grow. This method is favored for its efficiency in spat collection and growth rates, and its relatively low setup cost and labor demands 2 4.

Conservation and Bycatch Reduction

Modern long line procedures increasingly incorporate conservation measures. Integrated weights (IW) on lines, night setting, and bird-scaring devices (Tori lines) are used to minimize bycatch of seabirds and marine mammals, which can be attracted to baited hooks 1 3 9. Some fisheries switch from more harmful methods (like gillnets) to long lines to further reduce unintended captures 9.

Benefits and Effectiveness of Long Line

Long line systems offer diverse benefits: they can boost fishing and farming efficiency, reduce environmental impacts compared to other methods, and play a role in conservation.

Benefit	Description	Impact/Evidence	Sources
Selectivity	Targets specific species, reduces bycatch	Lower bycatch, better yield	5 6 9
Sustainability	Less habitat damage, efficient resource use	Reduced ecosystem impact	2 4 6 9
Conservation	Supports seabird and marine mammal safety	Drastic bycatch reduction	1 3 9
Economic	Higher profits, lower costs	Feasible for small-scale	4 5

Table 2: Key Benefits of Long Line Methods

Selectivity and Efficiency

Long lines allow for targeted fishing by adjusting bait, hook size, and deployment depth. This reduces unwanted bycatch—non-target species that can be harmed or killed unnecessarily. For example, long lines used for European catfish capture have a high catch-per-effort for target species and minimal bycatch compared to nets 5. In aquaculture, long lines provide improved spat collection and mussel growth, leading to better yields 4.

Environmental Sustainability

Compared to bottom trawling, long line fishing causes far less seafloor disturbance. Sensitive marine habitats, including vulnerable deep-sea coral communities, remain mostly intact even after decades of long line activity, whereas a single trawl can cause as much damage as hundreds or even thousands of long line deployments 6. In aquaculture, mussel long lines help improve water quality by removing excess nutrients 2.

Conservation Impact

Adding integrated weights and bird-scaring devices to long lines can reduce seabird mortality by up to 98% for certain species 1. Switching from gillnets to long lines in some fisheries has dramatically reduced bycatch of dolphins and sea turtles 9. Night setting further lowers risk to nocturnally active seabirds 3.

Economic Benefits

For small-scale farmers and fishers, long line methods can be more profitable than traditional alternatives. In mussel farming, long lines have lower setup costs and higher yields, resulting in nearly double the income per labor hour compared to stake culture 4. In fisheries, long lines balance economic viability with reduced bycatch penalties 5 9.

Risks and Side Effects of Long Line

While long line methods offer clear advantages, they are not without risks—to both target wildlife and the broader environment.

Risk	Description	Mitigation/Notes	Sources
Bycatch	Seabirds, mammals, turtles hooked	Weighted lines, Tori lines	1 3 9
Gear Entanglement	Streamer lines and mainlines can tangle	Careful deployment needed	3
Habitat Impact	Can affect benthic communities	Lower than trawling	6
Overfishing	If unregulated, stock depletion possible	Needs management	5 6 9

Table 3: Risks and Side Effects of Long Line Use

Bycatch Risks

Despite improvements, seabirds, dolphins, turtles, and other non-target species can still become entangled or hooked on long lines. Risk is highest with poorly designed or managed systems. Integrated weights and Tori lines, as well as night deployment, can greatly reduce bycatch, but only if implemented consistently and correctly 1 3 9.

Gear Entanglement

Bird-scaring lines (Tori lines) and mainlines themselves can become tangled, especially in poor weather or with improper setup. Such tangles can reduce fishing efficiency and still pose risks to wildlife if not quickly addressed 3.

Habitat and Ecosystem Impacts

Although the seabed disturbance from long lines is much less than trawling, there is still some risk to fragile benthic habitats, especially in deepwater deployments. Over time, even selective gear can impact sensitive species if not managed properly 6.

Overfishing and Stock Depletion

If long line fishing is not regulated with quotas, closed seasons, and careful monitoring, overfishing of target species may occur, undermining both ecological and economic sustainability 5 6 9.

Recovery and Aftercare of Long Line

Proper aftercare and management are crucial to ensure the sustainability and ongoing benefits of long line methods, whether in fisheries or aquaculture.

Aspect	Best Practices	Outcome/Importance	Sources
Gear Retrieval	Remove all gear after use, repair damage	Prevents ghost fishing	5 6
Habitat Check	Monitor for benthic impact	Sustains ecosystem health	6
Bycatch Care	Immediate release of non-target species	Reduces mortality	1 3 9
Stock Monitoring	Regularly assess populations	Avoids overexploitation	5 6 9

Table 4: Recovery and Aftercare Practices for Long Line Methods

Gear Maintenance and Retrieval

All gear should be retrieved after deployment to prevent "ghost fishing," where lost lines continue to trap wildlife. Regular inspection and maintenance of hooks, lines, and weights are essential 5 6.

Environmental Monitoring

Fisheries and aquaculture operations must periodically assess the seafloor and surrounding ecosystems for signs of damage or degradation. This allows for adaptive management and timely changes to practices if negative impacts are detected 6.

Non-Target Species Release

If bycatch occurs, immediate and careful release maximizes the chances of survival for non-target species. Training crews in safe release techniques is a vital aspect of responsible long line operations 1 3 9.

Stock and Yield Assessment

Ongoing monitoring of target fish stocks or farmed mussel yields ensures that harvest rates remain sustainable. Scientific surveys, catch data analysis, and collaboration with local communities help balance productivity with conservation 5 6 9.

Alternatives of Long Line

While long line methods are effective and increasingly sustainable, other fishing and aquaculture techniques exist—each with their own pros and cons.

Method	Pros	Cons	Sources
Gillnets	High efficiency, low labor	High bycatch (dolphins, turtles)	9
Bottom Trawling	Large catch volume	Severe habitat destruction	6
Stake Culture	Traditional, simple setup	Lower yields, less profit	4
Fyke Nets	Passive capture	More bycatch, less selective	5
Alternative Baits	Reduces pressure on bait fish	Not yet commercially viable	7 8

Table 5: Alternatives to Long Line Methods

Gillnets

Gillnets are widely used but notorious for high bycatch rates of marine mammals and endangered species. Studies show switching from gillnets to long lines can drastically reduce dolphin and turtle bycatch, while maintaining similar target fish yields 9.

Bottom Trawling

Trawling enables high catch volumes but at the cost of massive habitat destruction. Even a single trawl can do as much damage as hundreds or thousands of long line deployments 6. For many deep-sea environments, regulated long lining is a preferable alternative.

Stake Culture (Aquaculture)

Stake culture (using vertical poles in shallow water) is a traditional method for mussel farming. It has lower yields and profits than long line culture, making it less attractive for sustainable aquaculture development 4.

Fyke Nets

Fyke nets are passive fishing devices but tend to catch more non-target species and are less efficient for some target fish, such as European catfish 5.

Alternative Baits

Efforts to develop alternative baits for long line fishing, including manufactured and waste-based baits, are ongoing. While some show promise, especially for certain species, none yet fully match the effectiveness and commercial viability of traditional bait 7 8.

Conclusion

Long line methods, whether for fishing or aquaculture, are versatile, effective, and increasingly sustainable when best practices and modern innovations are applied. They offer a pathway to balancing human needs with ecological stewardship.

Key Takeaways:

• Long line procedures are adaptable and can be optimized for fishing, aquaculture, or conservation 1 2 3 4 5 6 9.
• Benefits include high selectivity, reduced bycatch, lower habitat impact, and economic viability for small-scale operators 1 2 3 4 5 6 9.
• Risks persist, mainly as bycatch and potential habitat impact, but can be mitigated with technology and careful management 1 3 6 9.
• Recovery and aftercare focus on gear maintenance, environmental monitoring, and stock assessment to ensure ongoing sustainability 5 6 9.
• Alternatives exist, but many are less efficient or have greater ecological drawbacks compared to well-managed long line systems 4 5 6 7 8 9.

By understanding and applying long line techniques responsibly, we can help secure a more sustainable future for our oceans and the communities that depend on them.