Four revolutions in tuna fisheries

As we are all well aware, fisheries industry has evolved, continuously seeking higher fishing efficiency whilst maximizing profit. Such an evolutionary progress has been achieved by the constant efforts of fishers and technological people. In the recent history of tuna fisheries, there were several milestones in their development
The first turning point refers to development of purse seiners. It occurred in the eastern Pacific Ocean in the 1960s. Off the US west coast, baitboat (pole-and-line) fishing had been harvesting tropical tunas until that point. In the late 1950s, hydraulic power block was invented, which generated development of the modern purse seiners in the early 1960s. Because of its very high efficiency, purse seiners rapidly replaced baitboats. The further development of purse seiners was accelerated with the increase of their fish holding capacity and with the start of setting nets on dolphin-associated tuna schools. As a result, the harvest level, as well as catch per unit of effort, jumped up.
The second important development is the conversion of the distant water longline fleet to a “sashimi” fleet. It occurred just around the same time in the 1960s. The invention of the super freezer (of a temperature below minus 40 degrees in centigrade) made it possible to provide tuna caught and frozen by the longliners to the “sashimi” market. Accordingly, almost all the distant water longliners started fishing tuna for the sashimi market, instead of fishing tuna for the canning industry. This change brought a very significant increase in the unit value of the catches and hence profit of the longliners.
The third milestone is the development of deep longlines. In the 1970s, longliners started to set lines at a much deeper layer than the traditional depth, targeting large bigeye tuna, which have higher unit value in the “sashimi” market. This is not as revolutionary as the other developments but it did change the longline operating procedures completely, including the use of at-sea transshipers.
The fourth revolution is the adoption of fish aggregating device (FAD) in the early 1990s. This technique was developed from fishing on tuna schools associated with natural floating objects. This fishing method evolved very rapidly, together with high technological innovations (e.g. sonars, satellite positioning, etc.) making purse seiners super-efficient, and markedly changed the catch compositions in regards to species and size of fish.
It is interesting to note that these four major changes increased the profits of these fisheries to a great extent. However, the two revolutions in purse seine fishery increased its efficiency but not values (per unit of weight) and increased an impact on the tuna stocks. The other two revolutions in longline fishery have not increased its efficiency but the value of its products and contributed for higher utilization of the tuna resources.
We should remember that the changes in fisheries are not limited to the improvements of profitability and/or efficiency but that there are many factors which reduce them. They are, for example, fishery regulatory measures, adoption of mitigation methods of by-catches and ban of drift gillnets. The fishery is maintained through a balance of these opposite impacts on the profit of fishers
What would be the next revolution? Hopefully, that would be the one to improve values of products. Is tuna farming the next revolution? 

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