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Purse Seine Guidebook

Purse-Seine Observer Coverage Requirements

For purse-seine vessels, although the details of the programs vary, in the WCPFC, IATTC, and ICCAT there are 100% coverage requirements (at least for certain geographical areas and/or times of the year and certain vessel sizes). In the IOTC, there is a 5% observer coverage requirement for vessels 24 m and greater in length overall operating on the high seas and for vessel less than 24 m if they fish in EEZs and on the high seas. Fishers operating purse-seine vessels in these RFMO Convention Areas must become aware of the specific applicable observer requirements.

Observers collect and report data on tuna catch, bycatch, and discards, among other things, through observer program worksheets and/or logbooks. In addition, some regions have port samplers who collect catch data as well. These data are an essential part of the scientific evaluation of the tuna fisheries and the ecosystem they inhabit. Skippers should ensure that observers and port samplers are given the access necessary to carry out these important duties.

Through Conservation Measure 4.3(a) on Observer Coverage, ISSF asks its participating seafood companies to conduct transactions with large-scale purse-seine vessels only if they have 100% observer coverage (human or electronic if proven to be effective).

Tag Recovery and Reporting

Tuna (and other fish) tagging programs have a number of uses, but almost all scientific tagging programs share a common goal: gathering data about fish.

Most tagging programs seek information on fish movements, growth, behavior, and mortality. This data is critical to scientists’ understanding of fish biology and for the creation of accurate models for stock assessments. Fishers might also encounter tagged seabirds, which will have small bands on their legs.

Simple tags have printed information and instructions on how to return the tag. These tags remain attached to the fish until it is caught or landed. Some high-tech tags monitor and record position and environmental data continuously. Some fish tags even pop off the fish at an appointed time, float to the surface, and transmit information via satellite.

If vessel crew catch or land a tagged animal, please take the time to remove the tag, note the time and location of the catch/landing, and ensure that the tag is returned to its owner. Often there are rewards for the return of tags — another reason to help contribute to the good management of your fishery.


Fishers must not remove the tags from live birds.