Let’s Talk Fishing Methods

If you’re new to my blog, please take a look at a previous article that you can find HERE. This describes the generally agreed upon framework for “sustainable seafood” and whether such a concept can exist at a commercial scale. You probably also know that I believe “sustainability” is also subjective – informed by personal experiences, preferences and perspectives. I’m asked a lot of questions about sustainable seafood. My hope is to help you demystify some of the more complex issues so that any perspective you prefer is adequately informed by truth and science. Everything I write is well researched, endorsed by subject matter experts and triple fact checked. Let’s dive in.




A question I get a lot is if there one “best method” for fishing? 

There are several factors to determine if any method of fishing is “sustainable” (I put sustainable in quotes because, as previously mentioned, it is a subjective matter). The simple answer is that each method has advantages as well as areas of concern. 

Commercial fishermen utilize a variety of methods and gear types for catching fish such as various longlines (bottom set, shallow set, deep set), gillnet, purse seine, trawl, pole and line, troll and handlilne. We will use tuna as an example here. 



Longline fishing, or longlining, uses a long line called the main line, with baited hooks attached at intervals.  Larger longliners can be tens of kilometers long and have thousands of hooks, while smaller inshore vessel have shorter lines, usually with under a thousand hooks. Bycatch of sharks, birds and turtles has been the biggest issue with this fishing method, however technology has improved sustainability. For instance, a weighted line considerably reduces the accidental catch of seabirds and a hook adaptation avoids turtles (circle shaped hook instead of J-shaped). Roughly 10% of total global tuna catch is attributed to longline fishing (source).




Longline fishing Source MSC



A gillnet is a wall or curtain of netting that hangs in the water. They can be set, or drifting. The holes are big enough to allow a fish to fit his head, but not it’s body, entangling him. Bycatch from gillnet fishing is very high across all species groups. Sharks, turtles, whales, dolphins, sealions and seals are the most common species caught in those nets. 

They are used predominantly in the Indian Ocean, being attributed to approximately 35% of the tuna catch of that region (4% globally). Gillnets are also accounting for a staggering 64 percent of shark catches (source) recorded in the Indian Ocean and the Indian Ocean’s dolphin populations may have declined by more than 80% since 1950 because of the use of drift gillnets to catch tropical tuna (source). Yikes. 

This is DESPITE restrictions and prohibitions on the use of drifting gillnets enacted by the United Nations in 1993. According to experts there is bycatch of approximately 175 dolphins per 1,000 tons of tuna. (Opinion Alert!) I usually try to present the facts and leave it up to you to arrive at your own conclusion but in this case, I’m just going to say outright: catching tuna, or most other species, with drifting gillnets is having significantly negative and unacceptable consequences on biodiversity. It is a big problem that calls for immediate international action and a boycott from consumers. The only acceptable use of gillnets is in salmon fisheries during timed runs as they have little bycatch (e.g. Bristol Bay). 




Gillnet Source MSC


Pole and Line

Pole and line is a fishing method used to catch tuna and other species one fish at a time. Typically, when a school of target fish is located, water is sprayed from the fishing vessel and small bait fish (e.g. sardines) are scattered, creating the illusion of an active school of prey fish.

Fishermen line up with a hand-held wooden or fiberglass pole with a short line and barb-less hook attached. Pole and line fishing has minimal to no bycatch of sharks, turtles and other sensitive species making it a very sustainable form of fishing for tuna. However, the carbon footprint is greater than “more efficient” fishing methods. Pole and line vessels sometimes also fish on Fish Aggregating Devices, usually anchored as opposed to drifting, but still have minimal bycatch of non-target species.  We’ll cover the impacts of drifting FADs in a moment. Roughly 8% of total global tuna catch is attributed to pole and line fishing (source).




Pole and line fishing Source MSC



A commercial trolling line is several lines hooked with natural or artificial baited hooks and is dragged by a vessel at the surface or at depth (weighted). It is considered a very selective fishing method. It represents about 2% of the world tuna catch (source).



Bottom Trawler

Bottom trawling is a fishing practice that drags a net along the seafloor. The mesh is designed to confine fish inside the net, trapping them in the end as the trawl is hauled to the surface. When you hear the word ‘trawler,’ very often that’s associated with destruction of the sea and pillaging because the nets indiscriminately haul up whatever they encounter while also destroying the seafloor. They can also be dauntingly gigantic. While it’s highly destructive nature is true in most cases, it should be noted that some research shows that in certain environments trawling can have some beneficial effects on the seabed, example sand, mud, gravel. (source). There are also trawl fisheries that have had to adapt to being more sustainable. That’s by example the case in the North Pacific groundfish fishery where a combination of off-limits Marine Protected Areas, mandatory independent observers and a system called catch shares which is like cap and trade for quotas has resulted in an environmental and social success in that fishery (source). This is great evidence of how cooperation and management can turn things around! Please note that this method is not used to target tuna but given the controversy surrounding trawl fisheries, I wanted to cover it.




Bottom trawler fishing Source MSC


Seafloor “scarring” of bottom trawling (source)


Purse Seine

The last method I will cover is the most efficient and commonly used method of catching tuna used in the world today. Purse seine tuna catch accounts for up to 66 percent of the world’s tuna (source). A purse seine is a large wall of netting deployed around an entire area or school of fish. The seine has floats along the top line with a steel line threaded through rings along the bottom and chains or weights at its bottom to allow the net to sink. Once a school of fish is located, a skiff encircles the school with the net. Then the net is closed underneath the school by hauling the purse line at the bottom. 




Purse Seine fishing Source MSC


Are all Purse Seines Created Equal?

When it comes to purse seines, I understand that the idea of a net surrounding a school of fish and grabbing them can appear to have a big impact, but the status of the target stock, catch of non-target species, and management measures in place, should all be considered before passing judgement.  Also, given the food needs of humanity and the importance of the ocean in helping to satisfy those needs, we should always think about the real impact of fisheries on a scientific level. That allows us to make better and more informed buying decisions that preserve healthy oceans.



There are several factors to determine if a purse seine is “sustainable”.



Here’s what they are:



  1. The Use of FADs (Fish Aggregating Devices) 

A FAD is a structure floating in the ocean with the purpose of, you guessed it, aggregating fish to make it easier and faster to catch them. A lot of industrial purse seiners use drifting FADS in tropical tuna fisheries. Many are equipped with echo sounders that give information about the biomass under the FAD. 


    • As the nets aren’t selective, they grab everything that’s around, creating a high amount of bycatch of juvenile and non-target species as well as sensitive species like silky sharks. By comparison purse seine fisheries that set on free-swimming schools of tuna have very little bycatch – with an average rate of less than 1%. When utilizing FADs, purse-seine vessels have bycatch rates from around 1% in the Eastern Pacific to nearly 9.5% in the Atlantic (source), though it is important to also consider cumulative impacts given the volume of tuna typically caught in large-scale purse seine fisheries.
    • There are other concerns with FADS like marine pollution and “ghost fishing” if the device is not recovered. Derelict fishing gear, sometimes referred to as “ghost gear,” is any discarded, lost, or abandoned, fishing gear in the marine environment. This gear continues to fish and trap animals, entangle, and potentially kill marine life, smother habitat, and act as a hazard to navigation. Derelict fishing gear, such as nets or traps and pots, is one of the main types of debris impacting the marine environment today (source). 
    • Environmental management of FADS includes setting limits on how many are used, using non-entangling nets that reduce “ghost fishing” and mitigating pollution through recovery of gear and the use of biodegradable materials. However, even when biodegradable FADS are used, plastic is still involved – usually for floatation. 
    • Some of the positives from use of FADs include considerably less carbon footprint per fish when compared to other methods. Also, less time at sea generally means best working conditions for fishermen on board. By setting FADs in certain target areas within a country’s exclusive economic zone, it’s possible to increase economic yield for the country, such as in the Pacific where coastal communities depend on catch and trade as a source of food and a defense against poverty. 


Are FADS good or bad? I’ve given you the unbiased information, now you judge according to what’s important to you because THAT’S WHAT SUSTAINABILITY IS ALL ABOUT. Also, eco-labels and certification schemes like the Marine Stewardship Council (MSC) go a long way to analyzing the benefits and tradeoffs, ensure traceability so that what you think you’re buying is actually what you’re buying, and help create a framework for unsustainable fisheries to take measurable action to improve the sustainability criteria and practices.




2.  The Management of the Species: Regardless of what method is being used to fish, a healthy ocean depends on sustainably managed fisheries. 


“Sustainable management” in fisheries terms relates to maximum sustainable yield (MSY). That is the largest average catch that can be captured from a stock under existing environmental conditions that balances between too much and too little harvest to keep the population abundant. To be noted that by referring to a fish population as “fully exploited”, it means that it’s fished within MSY, and not overfished. (source) (Opinion alert!). Whether the stock is abundant, subject to overfishing or overfished, it’s the management that matters most of all! That is because management can defend abundant fisheries from future harms and can also lead overfished populations to recovery. 


Check out my most recent rod & reel adventure hitting limits on 50-70lb Pacific bluefin tuna HERE .


Let’s use bluefin tuna as an example! Although Pacific-wide populations of bluefin are well below target levels, U.S. wild-caught Pacific bluefin tuna is a smart seafood choice. That is because it is sustainably managed under rebuilding measures that limit harvest by U.S. fishermen. Management of highly migratory species, such as Pacific bluefin tuna, is complicated because they migrate thousands of miles across oceans and international borders and are fished by many nations. NOAA Fisheries first determined the Pacific bluefin tuna stock to be overfished in 2013. Mandatory conservation and management were adopted to rebuild the stocks. To put it in perspective, in the IATTC convention area in 2021, the total catch limit was 3,925 metric tons. Of that, the US had a commercial bluefin quota of 425 metric tons (source). Mexico by comparison had 3,500 tons. Japan’s quota is predominately allocated in the Western Central Pacific convention area and was 8,889 metric tons in 2021. Collectively total catch across the Eastern and Western Pacific is being managed to allow the stock to recover.  



3.  Subsidies


This is when the government is providing some kind of support (monetary or costs breaks) to the private sector, serving a public purpose. In the fishing industry, it was a well-intentioned set up (or at least I’d like to think so), to reduce the amount of fishing vessels out at sea. But where there’s money, there’s always trouble. Especially that much (fisheries subsidies are close to 800M$ in the US alone and $35B worldwide).



Example of subsidies:

Fuel tax rebate

Investment grants

Access to landing sites free of charge

No license fee



Are subsidies actually helping? The proof is in the pudding. There is substantial evidence that subsidies are contributing to economic losses in the fisheries sector, create serious distortions in global fish markets and push fisheries beyond their realistic economical and biological models in addition to having a serious impact on food security and livelihoods, particularly in developing countries. (source)  The World Trade Organization (WTO) AND the United Nations (UN) have been fighting against them for over 20 years now. The FAO even stated that 20/$35B out of fisheries subsidies contributes directly to overfishing. 

Are they all terrible? Well, there is such thing as “beneficial subsidies”. They are financing management capabilities, R&D, surveillance and enforcement, etc. But I’ll let you judge if a small portion of good excuses a mainly detrimental practice. (I’ll dedicate a full post on this topic).



4. The Dolphin Safe Issue


 In the Eastern Pacific Ocean, particularly off the coast of Mainland Mexico, Central America, and Colombia, dolphins like hanging out with large yellowfin tuna. In the late 1950’s fishing boats became fast enough and some unscrupulous fishermen decided to chase down pods of dolphins then encircle them with their nets to catch the tuna, resulting in significant dolphin mortality. In 1987, biologist Sam LaBudde went undercover on a commercial tuna fishing vessel to document the ship’s offshore activities filming dolphins drowning in fishing nets. Absolutely horrifying! (source

To be dolphin safe certified, no dolphin must have been caught in the process. While most tuna sold in the US today is not caught in association with dolphins, there still are fishermen that target dolphins in the Eastern Pacific. Under the Inter American Tropical Tuna Commission Agreement on the International Dolphin Conservation Program (IATTC/AIDCP), there is a dolphin mortality limit (DML) of 5,000 animals per year. THEY ALLOW 5,000 DOLPHINS TO BE KILLED EVERY YEAR (not cool to have certified MSC, not cool). 

Dolphin interactions and mortality are regionally specific problems. As summarized, the Indian Ocean gillnet fishery and the purse seine fishery in some regions of the Eastern Pacific (not the US) are where the dolphin bycatch issues lie. Other than that, a Dolphin Safe label on tuna is as pertinent as gluten free would be to shampoo. The American fleet does not fish on dolphins, operates under the US Marine Mammal Protection Act, and closely follows the US Dolphin Safe Labelling Standards. The Marine Stewardship Council controversially certified the Mexican purse seine tuna fishery despite many objections (source). Unfortunately this means that if dolphin safe is a priority to you, you should look for the dolphin safe eco-label in addition to any other eco-label. 


Little parenthesis here, back on the topic of stock status, an RFMO—short for regional fisheries management organization—is an international body made up of countries that share a practical and/or financial interest in managing and conserving fish stocks in a particular region. These include coastal States, whose waters are home to at least part of an identified fish stock, and “distant water fishing nations” (DWFN), whose fleets travel to areas where a fish stock is found (source). Tuna RFMO’s and their relevant stock status follow: 


Tuna RFMOs:

CCSBT– Commission for the Conservation of Southern Bluefin Tuna

IATTC– Inter-American Tropical Tuna Commission

ICCAT– International Commission for the Conservation of Atlantic Tunas

IOTC– Indian Ocean Tuna Commission

WCPFC – Western and Central Pacific Fisheries Commission


Little side note, The IATTC: Inter-American Tropical Tuna Commission  includes resources of the United States, Canada, the EU, part of South America and Chinese Taipei. The IATTC is a very reliable organization including some the best scientists in the world, delivering content that is peer-reviewed and as scientifically accurate as possible. 




The western and central Pacific tuna fishery: 2019 overview and status of stocks https://fame1.spc.int/en/component/content/article/251


So ultimately by analyzing both the stock status and the impacts of the fishing methods covered above, one can arrive at conclusions on which regional methods are sustainable and which are unsustainable. But keep in mind this is dynamic and recommendations to consumers will change as the status of the stock changes or as fishing practices adapt. 


My recommendation would be that if you want to consume tuna fished within the regions included on the list above, here’s are good options in the US/Canada: 


  1. Pole and line-caught Yellowfin and Albacore tuna
  2. Family and/or small-scale fishery-sourced Yellowfin, Albacore, Skipjack tuna. 
  3. Purse seine FAD free, dolphin free and unassociated with subsidiaries Yellowfin and Albacore tuna. 
  4. Long liners (the right ones, aka the ones using sinking lines with O-shaped hooks) Yellowfin and Albacore tuna. 


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