Stock Assessment Workshop 19th June -25th June 2008 SPC Headquarters Noumea New Caledonia

Day 1 Session 1 Overview of tuna fisheries and stock assessment in the WCPO

What are the key features of the WCPO fishery relevant to stock assessment? Oceanic fisheries in the WCPO are complex Consider: Ecosystem /Oceanography Fisheries Species Political considerations Understanding the complexities across these factors is critical to building an appropriate model.

Climate and Oceanography Warm pool c) a) Global and Pacific climate varies both seasonally and interannually, the latter largely as a result of the El Nino Southern Oscillation phenomena, which see climate conditions shifting between El Nino, neutral and La Nina conditions. These climatic shifts accompany large scale oceanographic shifts, including the east-west movement of the Western and Central Pacific “warm pool” and the ecosystem associated with that. This climatic and oceanographic variability plays a major role in tuna movement and population dynamics, with flow on consequences for the fisheries that target them.

Climate and Oceanography La Nina Warm pool c) a) Cold tongue El Nino Warm pool

WCPO (Tuna) Fisheries Varied. How do you define them? WCPO-wide ? Domestic v Regional v Charter v Bilateral ? Near Shore v Distant Water? Commercial v Recreational v Artisanal v Illegal? Longline v Purse-seine v Gillnet v Troll v Handline v ? Tropical v Temperate ? WCPO tuna fisheries can be considered “super fisheries” with many smaller ‘sub-fisheries’. WCPO tuna fisheries are highly complex and pose challenges for stock assessments. This complexity is one of the reasons for using spatially structured models.

Target Species Multiple target species and gears complicates fisheries management decision making. Management measures to deal with one species generally have implications for the fisheries for other target species also.

Political Considerations

Yellowfin

Fish don’t respect borders You are here Bigeye

Relevance of stock assessment at the country level SA’s provide a regional perspective of the stock (e.g. BRPs) But in the estimation of BRPs, SA’s in the WCPO also provide estimates of; Biomass x region F x region R x region etc. These can be used to potentially provide information at a country level e.g. biomass/km2  biomass/EEZ Indicative catches at MSY/EEZ

Questions for discussion: How do regional level stock assessments provide useful (scientific and management) advice at the sub-regional and country levels ? How are the regional level stock assessments used in-country?