the humboldt current system of northern and central chile - figema

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MARTIN THIEL ET AL.productive EBCs (Halpin et al. 2004, Montecino et al. 2005), as a model system. In the presentpaper knowledge on the HCS in northern-central Chile is reviewed because this area is characterisedby a complex set of temporally changing and geographically variable conditions that represent aparticular challenge to science and management (see also Artisanal benthic fisheries and followingsections, p. 278ff). The aims of this review are 4-fold: to (1) review current knowledge, (2) revealgaps in information, (3) indicate conservation priorities, and (4) propose future research avenues.The HCS, by some authors named the Peru-Chile Current System, extends from ~42°S up toabout the equator (Montecino et al. 2005). The main oceanographic features of this system areoften described as cold nutrient-rich waters being transported northward and nutrient-enrichedsubsurface waters upwelled along the shorelines of Ecuador, Peru and northern Chile. Occasionallythe nutrient-supply engine of the HCS is interrupted by influx of warm and nutrient-depletedequatorial waters; during such events (El Niño, EN) the northward flow of cool nutrient-rich watersis suppressed and upwelling intensity is often reduced (W. Palma et al. 2006). Individual cycles ofthis El Niño Southern Oscillation (ENSO) last for several years, but predictability of EN events isstill very limited. On shorter temporal scales, there is a seasonal (predictable) pattern of climateand oceanography at high latitudes, which becomes aseasonal (and less predictable) at mid- andlow latitudes (Blanco et al. 2001, Carr et al. 2002). It can be argued that the predictability ofoceanographic conditions is lowest in the mid-region of the HCS (from 18°S to about 32°S; seealso Thomas et al. 2001a) because here the seasonal variations are occasionally overshadowed bythe interannual ENSO cycles, whereas at low latitudes (
THE HUMBOLDT CURRENT SYSTEM OF NORTHERN AND CENTRAL CHILE18°Fishery unitCHILEArica20°25°30°35°I - IIIII - IVV - IXIquique/Rio LoaMejillonesAntofagastaCalderaIsla ChorosCoquimbo(Lengua de Vaca)Punta Curaumillacentral ChileConcepciÓnGolfo AraucoIquiqueAntofagastaCoquimboValparaísoConcepciónNorthernCentralHUMB OLDT C URREN T SYSTE M40°ValdiviaChiloé45°50°X - XIISouthern55°Figure 1 Study region in northern Chile with the main upwelling regions and localities mentioned throughoutthe text. Principal upwelling centers in black dots, other sites with frequent upwelling indicated with greydots, coastal stretches with occasional upwelling shown as thick black line.that “lack of consistent trends among sites … shows that El Niño effects on interannual recruitmentvariation are not predictable”. Not only marine biologists but above all the organisms inhabiting theHCS are grappling with this limited predictability. How do these organisms deal with the difficultyof foreseeing the availability of dispersal windows, food, competitors or predators in the nearfuture? Many of the following sections will explicitly or implicitly address this question. The mainfocus, though, will be on the outcomes of ecological processes in the HCS, the processes thatgovern them and their relevance in a socioeconomic and conservation context.Variable distribution patterns and species interactions in the HCS are not only due to oceanographicprocesses but are also increasingly affected by human activities that reduce the abundanceof some species while favouring others. When humans first started to use the natural resources ofthe HCS, they opportunistically reacted to the system and exploited natural resources where thesewere available and accessible. When a particular resource became scarce or inaccessible they eithersearched for the resource in other places or shifted to alternative resources (e.g., Llagostera 1979,Méndez & Jackson 2004). With increasing population pressure and technological advances, humanpressure on the HCS has intensified. Wave-sheltered bays along the coast with dense human populationsare impacted by intense shipping traffic, artificial coastline constructions and wastewaterinflux (Fernández et al. 2000). Mining and agriculture activities have resulted in severe contaminationof some coastal areas, fishing pressure has intensified and extended into previously inaccessibleregions and zones and finally climate change (increased ultraviolet (UV) radiation, global warming)has also reached the HCS. From being opportunistic users who responded to natural variations inresource abundance, humans have now become important actors who directly affect many of the199
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