Over the last decade, the number of tuna purse seiners has increased, especially during the period 2011-2015.
The latter resulted from an announcement from ISSF that they would set a capacity limit on the Fish Hold Volume of tuna purse seiners > 335 m³.
ISSF is keeping a register, and if a boat owner you’re not in, the stakeholders (only canners) are not allowed to buy your whole round tuna. The shipyards were shortly after the announcement fully booked for three years on a row. The tuna purse seiners became bigger and bigger. At the same time, the owners ordered support vessels, to make sure that the catching effort of the big tuna vessels would be very economical.
In 2011 FHV was 781.000 m³ versus 870.000 m³ in 2019, an increase of 11% since the announcement to limit fishing effort. On top of this, developing countries still can add capacity, which they continue to do. This not done by the local population, but by Asian fleets, which sell most of their catch to members of ISSF.
The only way to limit fishing effort is to establish in each ocean:
Fishing vessels get equipped with better fish detecting equipment, buoys on FAD’s, fishing gear. Owners continue to upgrades their fishing vessels regularly during the lifetime of the fishing vessels. This development has to be taken into account when introducing limits for the fishing effort.
Fishermen prefer larger nets – longer and often reaching deeper in the water. To be more selective, it can that in times of difficulties with tuna stocks, to fish with either/or/and:
RFMO’s must not only focus on the technicalities but also align their efforts in limiting fishing capacity in various ways.