Ecosystem Considerations

The 1995 FAO Code of Conduct for Responsible Fisheries stipulates that “States and users of living aquatic resources should conserve aquatic ecosystems” and that “management measures should not only ensure the conservation of target species, but also of species belonging to the same ecosystem or associated with or dependent upon the target species”1. In 2001, the Reykjavik Declaration on Responsible Fisheries in the Marine Ecosystem elaborated these principles with a commitment to incorporate an ecosystem ap-proach into fisheries management.
Consistent with these instruments, one of the functions of the IATTC under the 2003 Antigua Convention is to “adopt, as necessary, conservation and management measures and recommendations for species belonging to the same ecosystem and that are affected by fishing for, or dependent on or associated with, the fish stocks covered by this Convention, with a view to maintaining or restoring populations of such species above levels at which their reproduction may become seriously threatened”.
Consequently, the IATTC has recognized ecosystem issues in many of its management decisions since 2003. This report provides a brief summary of what is known about the direct and indirect impacts of tuna fisheries in the eastern Pacific Ocean (EPO) on the populations of species and ecological functional groups and the structure of the ecosystem, as controlled by the strength of predator-prey interactions.
This report does not suggest objectives for the incorporation of ecosystem considerations into the man-agement of fisheries for tunas or billfishes, nor any new management measures. Rather, its main purpose is to demonstrate that the Commission considers the ecological sustainability of the fisheries which it manages.
However, the view that we have of the ecosystem is based on the recent past; there is almost no infor-mation available about the ecosystem before exploitation began. Also, the environment is subject to change on a variety of time scales, including the well-known El Niño fluctuations and more recently rec-ognized longer-term changes, such as the Pacific Decadal Oscillation (PDO) and other climate-related changes.
In addition to reporting the catches of the principal species of tunas and billfishes, the staff estimates catches (retained and discarded) of non-target species. In this report, data on those species are presented in the context of the effect of the fishery on the ecosystem. While relatively good information is available for catches of tunas and billfishes across the entire fishery, this is not the case for bycatch species. The information is comprehensive for large2 purse-seine vessels that carry observers under the Agreement on the International Dolphin Conservation Program (AIDCP), and some information on retained catches is also reported for other purse-seine vessels, and much of the longline fleet (see SAC-08-07b). There is little information available on bycatches and discards by fishing vessels that use other gear types (e.g. gillnet, harpoon, and recreational gear (see SAC-07-INF-C(d))).
Detailed information on past ecosystem studies can be found in documents for previous meetings of the Scientific Advisory Committee (e.g. SAC-08-07a), and current and planned ecosystem-related work by the IATTC staff is summarized in the Strategic Science Plan (SAC-09-01) and the Staff Activities and Research report (SAC-09-02).