Nomadic Tuna Ranching

Tuna are built for speed. With a sleek stream-lined silhouette and powerful muscles, they slice through the water at speeds up to 50 mph.

A mature tuna can be up to 3 meters from mouth to tip of tail, and some weigh in over 600kg – heavier than a horse.

Even as they dart through the frigid ocean depths, they maintain a core temperature several degrees above that of the surrounding waters. They are one of the few warm-blooded species of fish.

Tuna are pelagic, which means they live in the deep sea, away from coastal waters. They must continually move to breathe and are constantly on the hunt for food; they can dive over 1000 meters in their search for a meal. They are found in all the temperate and tropical areas across the world’s seas (blue and green areas on map, right).

Tuna live primarily in international waters, beyond the 200-mile coastal waters of nations. For this reason, tuna stocks do not belong – and are also not managed – by any country.

The demand for tuna is high; recently a single tuna at the famous Tokyo Tsukiji fish market was sold for $1.8 million.

Unfortunately this means that many tuna species are critically exploited. For example, currently the Southern Bluefin Tuna (Thunnus maccoyii) is endangered due to overfishing by commercial trawlers.

To fish tuna sustainably, the next step is for nations to develop methods that go beyond “hunting and gathering”. In the story Pelagia, set fifty years in the future, the nomadic Battuta family and their clan earn a living by ranching the Bluefin tuna as they follow them in their migratory route around the Southern Pacific Gyre.

Tuna, like all finfish, have a special sense which humans lack. A stripe stretching the length of their body – called a lateral line – allows them to sense movement, vibrations, and changes in pressure in the water around them. This sense plays an important role, for example, in how fish behave as they school together to hunt for food and evade predators.

The sea-steading communities in Pelagia ranch tuna by first spawning and raising large groups of the young in hatcheries. Each of these groups is conditioned to follow a unique pattern of pressure pulses. This is much like a flock of sheep who are trained to follow a lead sheep with a bell around its neck (known as a bellwether sheep).

The bellwether for each cohort of juvenile tuna is a robot. Instead of a ‘bell’, it regularly emits a pressure pattern as it leads its cohort to food; the robotic tuna is able to detect the best feeding ground as they pass through sections of the Southern Pacific Gyre. It is also equipped to monitor the behaviour of its cohort as well as protect it from predators.

In Pelagia, each robotic bellwether tuna is managed by an ‘augmented intelligence agent’ (A.I.) — one of whom is named Nemo. The A.I. track the health and development of the tuna schools, identifying when a school is ready for harvest. In this way, not only is an endangered species replenished, but it becomes a sustainable food source and exportable commodity to support the lives of the sea-steading communities.

This technology the communities in Pelagia rely on is within our reach today. My hope is that ideas like this will inspire us to ways we can contribute to restoration and sustainability of our marine environment.

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