On The Boat

onthebota0 There are many ways to catch fish. Some techniques only catch the intended species while others also trap unintended species resulting in injury and death to many sea creatures, some of which are already endangered. This is referred to as by-catch.

There are five principle kinds of fishing methods:

  • Pole and Line Fishing
  • Troll Fishing
  • Purse Seine Fishing
  • Long Line Fishing
  • Trawl Fishing

Here is a summary discussion of these methods. Click illustrations to magnify.

  • Pole & Line FishingPole & Line Fishing
  • Pole and Troll FishingTroll Fishing
  • Purse Seine FishingPurse Seine Fishing
    1. Fish schools encircled
    by large net
    2. Net closed off at base,
    like a purse,
    3. Fish captured along
    with by-catch of
    non-targeted sea life
  • WP-FAD-Illustration-Transparent_REDFADs
  • Long Line FishingLong Line Fishing


There are 2 main methods used to catch tuna in commercial fisheries that Wild Planet endorses
as the best practice methods:


Pole and Line

Pole and line fishing has been practiced for centuries in several different parts of the world. The method involves attracting a school of tuna to the side of a “bait-boat” by throwing live sardines and anchovies overboard.  This creates a tuna “feeding frenzy” and fish are hauled out of the water, one-by-one, using pole and line.  The size of the tuna caught this way is small, mostly consisting of albacore and skipjack, but also some yellow fin tuna.


“Trolling” means to catch fish by towing a lure or baited hook behind a slow-moving boat. In the albacore fishery, trollers attach ten to twenty fishing lines to the vessel’s outriggers.  These fishing lines are of different lengths and are also spread out along each outrigger to help prevent them from getting tangled up with each other.

Attached to the end of each line is a jig, which is a rubbery fishing lure with a hook in it.  Jigs are shaped to look like squid and come in a wide variety of colors.  The jigs are trailed in the water behind a moving boat, and some albacore will bite a squid-like jig and get hooked.  The hooked albacore is immediately removed from the water and prepared for freezing.

Because jigs are designed to catch fish on the ocean’s surface, they simply cannot reach the older, larger albacore that swim in deep waters far below the surface.  This is why other types of fishing gear are used to catch older albacore, and why “troll-caught albacore” always refers to the younger, smaller, surface caught Omega 3 rich albacore that are also demonstrably lower in mercury than deep water larger albacore due to fewer years of feeding in the food chain.

To learn more, please refer to the Oregon State University study: OSU Mercury Study.

These comments about surface caught albacore apply equally to the albacore caught by the other ecologically exemplary method – Pole and line.


There are two additional tuna harvest methods that Wild Planet considers as environmentally inferior and not in compliance with optimum conservation of marine resources:

Purse Seines with FADs

Go to Monterey Bay Aquarium Seafood Watch Seafood Guides to get the facts on how harmful this method can be.

Purse seines are large nets that can measure over 2 km long and 200 meters deep. They are deployed in a circular form around a school of tuna, hanging vertically in the water column.  Once the fish are completely encircled by the net, it is drawn tight at the bottom, like a purse, to prevent the fish from escaping below.  It is then brought alongside the fishing vessel, hoisted out of the water, and the fish are brought on board.  Purse seines are used to target mostly yellowfin tuna and skipjack, and on a world scale account for roughly 60% of all the tuna landed.

Purse seine fishing when practiced on free-swimming schools of tuna without the association with FADs (Fish Aggregating Devices) has a moderate by-catch mortality percentage.  However, when practiced in connection with FADs, purse seining results in very high by-catch mortality of non-target species and non-target size tunas.  The percentage of baby tunas caught prematurely in the FAD fisheries is likely the most serious problem facing tuna fishing.  When tiny tuna are taken at a fraction of their mature weight the potential tuna yield of the oceans is prevented.

To illustrate the gravity of the problem of prevented yield, there are hundreds of millions of pounds of tiny tunas taken in FAD purse seine fishing operations globally.  For the sake of a conservative argument, let’s assume the number is only 100,000,000 pounds.  If the tiny tuna (mostly yellow-fin and big eye) are caught at an average weight of 5 pounds instead of growing up to an average mature harvest size of 50 pounds, then the premature capture by FAD that we call “Tuna Infanticide” prevents the additional yield of 900,000,000 million pounds of tuna.  That is a billion dollars worth of tuna and a lot of sushi or grilled tuna steaks!


Long-line fishing is the most common method used to catch albacore worldwide.   Long-lines attract a variety of open ocean swimmers, such as endangered sea turtles, sharks and other fish, resulting in wasteful by-catch* mortality.  Also, as the line is deployed into the water, seabirds dive for the bait, are ensnared on the hooks and drown.  Since there are no integrated international laws to reduce by-catch, international long-line fleets are contributing heavily to the long-term decline of some of these threatened or endangered species.

Long-line gear involves the use of a main line of up to 150 km in length from which as many as 3,000 shorter branch lines, each with a baited hook, are dangled in the water column.  The mainline is kept afloat by a series of buoys attached at intervals.  The gear is passive, in that it captures whatever fish happen to take the bait.  Long-lines operate mostly at depths between 100 and 150 meters, but can be set as deep as 300 meters when targeting big eye.  Long-lines are used to catch the high-value fish that are marketed as sashimi, historically in the Japanese market but also increasingly in North America and Europe.  Since very high quality fish is needed for sashimi, most vessels are equipped with “flash freezers” to freeze the fish to -60oC almost immediately.


Most fisheries catch unwanted animals along with their target catch. This non-target catch, known as “by-catch”, is normally thrown back into the ocean, dead or dying.  Tuna fishing is no exception to this rule.  Long-lines, for instance, can catch sharks, rays, sea turtles, seabirds and many species of fish.  Globally, it has been estimated that 200,000 loggerheads and 50,000 leatherback sea turtles are hooked by long-lines every year.

Purse seines, when used in conjunction with floating objects (known as fish aggregating devices, or “FADs” – used to attract schools of tuna), add to by-catches consisting of a diverse array of marine life, including dolphin fish, billfish, wahoo, triggerfish, barracuda, rainbow runners, sharks, sea turtles and baby tunas.


In most cases, canned tuna labeling does not include information on the catch method. If it is absent, you can likely assume the worst.


There is virtually no by-catch (<0.5%) associated with the trolling or pole and line techniques, which are regarded as the best fishing methods for tuna, a fact worth remembering when you buy.  Pole and troll caught tuna are considered the very best method for sustainability by a consensus of many Non-Government Environmental Organizations (ENGOs).

Wild Planet is proud to be in compliance with the green standards of Monterey Bay Aquarium Seafood Watch, Blue Ocean Institute, Ocean Wise, Sea Choice and Fishwise.  Greenpeace has also evaluated Wild Planet tuna products and has rated them as a top brand for sustainable sourcing policies.

For a more detailed discussion of the history of Wild Planet’s sourcing policy, please see the document: Wild Planet Procurement Policy 2.2017


The use of purse seines or drift nets without FADs as fishing methods are successful and sustainable catch methods for certain schools of fish.

The fisheries Wild Planet uses to catch our salmon have outstanding management and make sure they are only harvesting salmon that can be yielded. The pink salmon are caught via purse seine operations while the sockeye salmon are caught via drift net operations. The salmon are then canned on the spot the same day they are caught.

Wild Planet uses similar purse seine methods to catch our sardines, anchovies, mackerel and yellowtail. We use single species targeted purse-seine fishing methods, which virtually eliminate by-catch of other species while also benefiting the overall marine ecosystem.


Trawl Fishing

This method is common in taking fish dwelling on the ocean bottom and mid-water in the water column. Groundfish like sole and rockfish are taken this way. Shrimp, hake (whiting) and pollock are also caught off the bottom by this same method of pulling a large-mouthed net like a gigantic sock through the water. Fish become trapped at the end of the net and usually cannot swim back out of the net.

This method has been very destructive in the past as it has caused much damage to the ocean bottom and has been fraught with large by-catch/discard problems. In recent years, however, there have been improvements in some of these fisheries. An example is the West Coast Pink Shrimp fishery, which has introduced fish excluders at the opening of the net which strike the fish and cause them to flee ahead of the net. This has dramatically reduced by-catch and made this Pink Shrimp trawl fishery and example of sustainable fishing practice. From this fishery Wild Planet sources its canned Pink Shrimp. Since no other Wild Planet products are caught by this method, we will not dwell further on this method here.