the humboldt current system of northern and central chile - figema

THE HUMBOLDT CURRENT SYSTEM OF NORTHERN AND CENTRAL CHILEits complex reproductive biology, which starts with reproductive aggregations for copula, the layingof egg capsules in which the larvae develop for about 30 days, then followed by a 3-month periodof pelagic life, the result is high recruitment variability at temporal and spatial scales, dependingon coastal oceanography and topography, and the potential for retention areas (Stotz 1997,J. González et al. 2004) (Figure 24). Larvae settle and metamorphose mainly on adult barnaclescovering adult shells (Manríquez et al. 2004) or in association with recently settled barnacles (Stotzet al. 1991b), which may vary greatly between years and sites (Stotz et al. 1991a). This producesa very complex metapopulation structure (J. González et al. 2004, 2006). However, given its longlife, with individual growth varying greatly (depending on food availability), fluctuations becomepartly attenuated when the individuals finally recruit to fisheries at an age between 3 and 4 yr witha size of 10 cm of peristomal opening length (Pérez & Stotz 1992, Stotz & Pérez 1992, Stotz 1997).Thus, while spatial variability of the fisheries is great, the temporal variability at each site becomespartially attenuated (Figure 22C after 1996), with fluctuations at the level of two to three times,which nevertheless means significant changes in the income for fishermen (Figure 24, harvest inAMERBs). The establishment of AMERBs, which was mainly motivated by the closure of the locofishery at the same time (1989–1992), coincided with a period of increased loco stocks along mostparts of the central Chilean coast, probably favoured by the closure and a short period in whichfishermen agreed to strictly obey that measure (Stotz 1997). The relationship of the number offishermen to the size of the management area was at that time generating an acceptable income,but this situation has mostly changed drastically in the following years. At present, many fishermenlocated at coastal areas with low production are dissatisfied and willing to abandon their AMERBs(compare magnitudes of harvest of AMERBs and number of fishermen in the organisation, shownin Figure 24).Sea urchin fisheryThe urchin Loxechinus albus fishery in the HCS between 18°S and 35°S is perhaps one of the mostvariable ones, in this case natural variability probably being increased as a consequence of captures.In central Chile (Regions IV–VIII), urchins are restricted to shallow areas with great surge on theexposed coast, in which the species is partly safe from the predation of the rock shrimp Rhynchocinetestypus (Stotz 2004), a species with abundance and distribution pattern that responds to thevariable existence of refuges from its own predators (Caillaux & Stotz 2003). This produces a verypatchy distribution of sea urchins. Recruitment occurs mainly inside the adult aggregations, whererecruits are protected by the spine canopy (Stotz et al. 1992). Thus, when fishermen, takingadvantage of calm weather conditions, reduce the stocks, subsequent recruitment is probably heavilyaffected. The observation is that once a site is fished for this species, it only recovers about 10 yrlater (Stotz 2004). Further north (Regions I–III, mainly between 20°S and 23°S), the fluctuationsattenuate slightly and landings increase, as large Macrocystis beds appear (Stotz 2004). There, amore conservative exploitation is carried out inside the AMERBs, conserving patches, and thisstrategy has allowed an increase in numbers, the sustainable exploitation of which nevertheless stillneeds to be demonstrated (Figure 22D).Resource dynamics and management of artisanal benthic fisheriesThe great natural spatial and temporal variability of resources, and hence fishery production, whichcharacterises the HCS between 18°S and 35°S, poses a great challenge to management. Fishermen,through AMERBs and legal restrictions, are not allowed to move away when a resource goesthrough a low cycle, as they used to do in the past. Illegal movement, though still occurring, isalso increasingly prevented in practice by conflicts with the respective local fishers. This produces283