the humboldt current system of northern and central chile - figema

THE HUMBOLDT CURRENT SYSTEM OF NORTHERN AND CENTRAL CHILEwith SST anomalies (Yáñez et al. 2001); also chub mackerel landings seem to correlate with SST(Figure 27). In contrast, interannual variations in the landings of the other three species seem tobe largely independent of variations in SST (Figure 27). The stabilisation of maximum anchovylandings between 1.5 and 2.7 million t during the 1990s and the parallel decline of the landingsof the Pacific sardine in the HCS (and the entire southeastern Pacific) reflects another regime shiftfrom the warm ‘sardine regime’ to a cool ‘anchovy regime’ (Chavez et al. 2003, Alheit & Niquen2004, Halpin et al. 2004). These regime shifts occur on multidecadal scales and are probably relatedto the PDO, but the mechanisms driving these changes are not yet well understood.Silva et al. (2003) studied the relationship between chl-a concentration, SST, and fishing yieldsof anchovy, Pacific sardine and jack mackerel in northern Chile during summer and autumn 1999.CPUE superimposed over SST images confirmed that the anchovy has a more coastal distributionthan Pacific sardine and jack mackerel, being found in the frontal zone of coastal areas. In thesoutheastern Pacific, the jack mackerel is a heavily exploited pelagic species, and its presence inthe HCS in autumn and winter is assumed to be mainly due to an inshore feeding migration(Bertrand et al. 2004). During warmer years, jack mackerel may immigrate into coastal waterswhere they are thought to exert high predation pressure on anchovy (Alheit & Niquen 2004).Changes in SST associated with EN events may also affect the migration pattern of jack mackerel,which needs to be taken into account in stock assessment and management plans (Arcos et al. 2001).Management of pelagic fisheriesAccording to Aguilar et al. (2000) the traditional method used to conserve fish stocks and preventoverfishing is to set a TAC for the fishery. Typically, TACs aim to restrict fishing effort to its MSY(maximum sustainable yield) level. Once these ‘safe biological limits’ are reached, fishing isprohibited. But TACs do not, by themselves, address the overcapitalisation issue. Consequently,many fisheries economists recommend that the designated TAC is distributed to industry participantsin the form of individual transferable quotas (ITQs), quasi property rights that restrict additionalaccess to the fishery. Under these rules, failure to acquire an ITQ effectively forces vessels out ofthe fishery, thereby reducing fishing effort and increasing harvesting efficiency.The Chilean General Law of Fisheries and Aquaculture considers three types of access to thefishery: (1) Full Exploitation Regime, which includes setting an annual quota or TAC by fishingunit, which can be temporally divided during the year and also modified once during that sameperiod (once the full exploitation regime is assigned to a given species no more fishing vessels areallowed to enter the fishery); (2) Recovering Fishery Regime is the fishery under a state ofoverexploitation, subject to a capture ban of at least 3 yr, to obtain its recovery and where an annualquota (or TAC) can be established; and (3) Early Developing Fishery Regime, which is a demersalor benthonic fishery with open access where an annual quota can be established and where nofishing effort is applied or if it is done it is less than 10% of this quota.In 1993 the first pelagic fisheries in Fisheries Unit I–II were assigned the status of FullExploitation Regime, and by 2000 this had extended to four of the five fisheries (anchovy, jackmackerel, Pacific sardine and common sardine) and to all fisheries units. The chub mackerel is oneof the few commercial species that is still under ‘open access’, with no regulation to date.Alternative management tools have been developed and used in the last years: in 1998, the useof a geographical positioning system for the industrial and artisanal fleets was established; later in2001 the Límite Máximo de Captura por Armador (LMCA, maximum capture limit per owner)was introduced for the industrial fleet in the fisheries for the small pelagics anchovy, sardines andjack mackerel in all fishery units, which is essentially an ITQ, and at least had the effect of reducingthe fishing fleet. The LMCAs are determined using captures (1997–2001) and corrected holdcapacity (authorised hold capacity in cubic metres times authorised area length divided by total291