Sustainability and Sourcing


How was your tuna caught?

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


There is virtually no by-catch 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. This eco-consensus is supported by many Non-Government Organizations (NGOs) including:


There are two main methods used to catch tuna in commercial fisheries that Sustainable Seas endorses as a best-practice method:

1. Troll-Caught Albacore

Commercial fishing vessels that harvest younger surface-swimming albacore are called jig boats because they fish with jigs. They are also called trollers since they troll for albacore.

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.

2. 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 baitboat 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 yellowfin and bigeye.


Sustainable Seas considers these two tuna harvest methods as environmentally inferior, and not in compliance with optimum conservation of marine resources:

1. Purse Seines

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 the majority of all the tuna landed. 

2. Longlines

Longlining is the most common method used to catch albacore worldwide. Longlines attract a variety of open ocean swimmers, such as endangered sea turtles, sharks and other fish, resulting in wasteful by-catch. Also, as the line is deployed into the water, seabirds dive for the bait, are ensnared on the hooks and drown. International longline fleets are contributing heavily to the long-term decline of some of these threatened or endangered species.

Longline 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. Longlines operate mostly at depths between 100 and 150 metres, but can be set as deep as 300 metres when targeting bigeye tuna. Longline is a principal way that the conventional industry catches larger, deep-swelling albacore tuna.



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. Longlines, 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 longlines every year.

Purse seines are no better, with bycatches consisting of a diverse array of marine life, including dolphin fish, billfish, wahoo, triggerfish, barracuda, rainbow runners, sharks and sea turtles, especially when used in conjunction with floating objects (known as fish aggregating devices, or "FADs" - used to attract schools of tuna).