the humboldt current system of northern and central chile - figema

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MARTIN THIEL ET AL.EN events, the recovery of local macha beds can be extremely slow, as observed in Peru (Arntzet al. 2006).The ‘loco’ fishery (sold as ‘Chilean abalone’ in international markets)The loco fishery makes use of the muricid gastropod, Concholepas concholepas, described as atop predator in the intertidal systems (Castilla & Paine 1987), but with its fished populations mainlyoccurring in the subtidal zone (Stotz 1997). In such areas and given that its main prey items aresuspension feeders (barnacles, tunicates), the species appears more as a browser, through its preytaking advantage of high PP in the water column near upwelling areas (Stotz 1997, Stotz et al.2003). Thus, production and consequently fishery landings vary greatly along the coast, with mainlanding sites coinciding with the most important upwelling areas (Figure 24) (Stotz 1997). GivenHigh larval retention withnormally intense recruitmentModerate larval retention withtemporally variable recruitmentPoor larval retention with weakand sporadic recruitmentUpwellingHarvest (ind)500,000400,000300,000200,000100,0000Harvest AMERBPta. ChorosN° fishermen = 1501999 2000 2001 2002 2003 2004ChañaralCalderaLoco productionHuascoHarvest (ind)25,00020,00015,00010,0005,0000Harvest AMERBPto. OscuroN° fishermen = 301999 2000 2001 2002 2003 2004Pta.ChorosCoquimbo?AMERBHarvest (ind)100,00080,00060,00040,00020,0000Harvest AMERBÑagueN° fishermen = 481999 2000 2001 2002 2003 2004Los Vilos0 200 400600 800Average annual landings (t yr −1 )Figure 24 Concholepas concholepas: Variability of larval retention and recruitment along the coast of RegionsIII and IV, production (average of the period 1985–1995) along the coast of Region IV and harvests of threeAMERBs located at coastal areas differing in production (note the scale of y-axis). (Figure adapted fromJ. González et al. (2004) and Stotz (1997)) Harvest data of AMERB obtained from SERNAPESCA (www.sernapesca.cl); stars show for Region IV the approximate locations of the AMERBs, ‘Area de Manejo yExplotación de Recursos Bentónicos’ (MEABR, Management and Exploitation Area for Benthic Resources).282
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
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the humboldt current system of northern and central chile - figema

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