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Oceanographic Variability
Tuesday, 14 April 2009 11:34

Oceanography (e.g. water temperatures, currents, productivity, etc) and climate dynamics have major influences on fish population dynamics and fisheries (Lehodey et al., 2006) in addition to any fishery impacts. Ocean-climate systems have been shown to strongly influence tuna fisheries in the Western and Central Pacific Ocean (WCPO) at various spatio-temporal scales and in different ways (Bour et al., 1981, Lehodey et al. 2003, Lehodey et al., 2006). Changes in oceanography may influence vertical and horizontal movements of tunas and other species, as well as eggs and larval survival. Individual tuna species display different preferences (e.g. preferred temperature) and thus will respond differently to changes in oceanography and climate (Fromentin and Fonteneau, 2001). While beyond the control of fishery managers, it is important to take into account the influence of oceanography and climate in order to better manage fisheries. Globally, tuna catches are highest in the western equatorial Pacific warm pool, a region characterized by low primary productivity and the warmest surface waters of the world’s oceans. However, the WCPO displays remarkable dynamics in oceanography mostly linked to climatic changes (such as El Niño Southern Oscillation, ENSO). In response, variations in tuna catches are reported at both regional and domestic scales both seasonally and inter-annually. The major oceanographic processes that impact on tuna distribution and abundance include in the WCPO are briefly discussed below.

Tuesday, 14 April 2009 11:35

The Oceanic Fisheries Programme of the Secretariat of the Pacific Community has recently completed a study on tuna fisheries around seamounts in the WCPO. This research is part of the Pacific Islands Oceanic Fisheries Management Project which is supported by Global Environment Facility (GEF).  Biodiversity on seamounts is high for benthic communities and they are considered important in the conservation of marine ecosystems.  Little however is known about their importance for pelagic species such as tuna. The study was undertaken in 3 parts:  the first used remote sensing data and existing literature to identify and validate the location of all seamounts in the western and central Pacific Ocean; the second examined whether tuna catch was higher on seamounts as opposed to coastal or other oceanic habitats and the third analysis examine whether pelagic biodiversity was higher on seamounts than coastal or other oceanic habitats.



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