Managing the floating-object fishery for tropical tunas in the EPO: supporting information for the precautionary additional measures recommended

The IATTC staff’s 2020 risk analysis (SAC-11-08) for the tropical tuna fishery in the EPO indicates that the current management measures (C-17-02), which expire at the end of 2020, are adequate in the short term. Nonetheless, the staff is recommending additional precautionary measures to ensure that these status quo conditions—defined as the average fishing mortality (F) during the most recent 3-year period (2017-2019)—are not exceeded, for two reasons:
1. For bigeye tuna, the risk analysis estimates a 50% probability that current fishing mortality (Fcur) is higher than the target reference point of maximum sustainable yield (MSY). However, the results of the risk analysis are bimodal (SAC-11-08), with a more pessimistic and a more optimistic group of models. The combined models in the pessimistic group indicate a 10% (or slightly higher) probability that the limit reference point has been exceeded;
2. Stock status indicators (SAC-11-05), in particular those for the floating-object (OBJ) fishery, show long-term trends that could lead to increased F in the near future, thus jeopardizing the desired effect of the current measures for the purse-seine fishery (72-day closure, the corralito closure, daily active FAD limits per vessel).
Although several types of management measures could be considered (e.g. measures described in IATTC-90 INF-B; IATTC-90 INF-B Addendum 1), the staff has focused on the following four options, all directly applicable to controlling F, and/or already implemented in some form:
1. limit the number of floating-object (OBJ) sets;
2. adjust the limits on daily active FADs;
3. limit FAD deployments; and/or
4. adjust the duration of the closure to compensate for increases in OBJ sets.

The staff reviewed the advantages and disadvantages of each option, as well as potential solutions to mitigate or compensate the disadvantages. The staff weighed the management benefits against data and infrastructure shortcomings, which led it to conclude that a limit on floating-object sets for all purse-seine vessels, combined with individual-vessel daily active FAD limits, would be the best option for maintaining the status quo and thus preventing an increase in F within a management cycle. How the limit on the number of floating-object sets would be allocated among CPCs2 or among vessels, or by some other ar-rangement, is a matter for the Commission to decide.