In the latest study (2017-19) misreporting of catch and harvest of tuna contributed an estimated 89% of the volume of IUU fishing.
Most of this misreporting was in the purse-seine fishing sector, where there is 100% observer coverage providing good independent estimates of catch. However, it can be challenging to identify species and estimate catch at sea due to the scale of the catches.
Only 5% of the overall estimated IUU volume was thought to be due to the various forms of unlicenced fishing. Few unlicensed fishing vessels were detected or prosecuted during the study period, except for incursions by illegal boats on the western fringe of the FFA area. Non-compliance with licence conditions and post-harvest regulations were each estimated to account for another 3% of IUU.
Purse-seine fishing in the Pacific accounts for most IUU by volume (worth some $152m), largely through misreporting. However, with 100% observer coverage for this fishery, any errors in catch reports can be picked up. Purse-seine vessels are also licensed to access the fishery through the Vessel Day Scheme, which means direct revenue loss associated with misreporting is likely to be negligible.
The study notes that the purse seine fishery is subject to comparatively strong MCS measures, but that future priorities could include:
- Ensuring there are good systems in place to validate catch composition
- Developing a catch documentation scheme, which identifies the provenance of tuna sold to market
- Controlling use of Fish Aggregating Devices (FADs) by registration and tracking, and setting up a FAD buoy register.
While there is less volume of IUU estimated for longline fisheries, their target tuna catch of big eye and southern albacore tuna is more valuable so IUU in these fisheries is worth more than half of the total estimated IUU by value (about $181m).