Browsing by Author "BUSTAMANTE, RH"

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    HUMAN EXCLUSION FROM ROCKY INTERTIDAL OF LAS-CRUCES, CENTRAL CHILE - EFFECTS ON DURVILLAEA-ANTARCTICA (PHAEOPHYTA, DURVILLEALES)
    (1989) CASTILLA, JC; BUSTAMANTE, RH
    On the exposed rocky shores of central Chile there exists a continuous small-scale harvesting of bull-kelp Durvillaea antarctica, by ''mariscadores'' (shellfish and algae gatherers). These harvest both fronds and stipes for human consumption. To assess the effects of human activity on D. antarctica populations, the density, standing crop and size structure of the kelp were compared in non-harvested (fenced) and regularly harvested (unfenced) areas. Both coastal mainland and small islands were included in the fenced and unfenced areas. Unfenced islands were expected to receive less human disturbance than unfenced mainland areas, because the islands were less accessible to harvesters. Populations of kelp underwent great fluctuations in abundance throughout the study period. Comparison between harvested and non-harvested areas revealed significant differences in density, biomass and size structure. In contrast, no significant differences were found between nearshore islands inside and outside the fenced area. Sources of variation in abundance of populations correspond to recruitment, natural mortality and harvesting, especially in harvested mainland areas. Interaction between time and extent of exploitation is significant when D. antarctica biomass is considered. The existence of protected areas (coastal preserves) and of areas of difficult access to mariscadores (refuges or ''bufferzones'') allows the preservation of populations and facilitates re-population of harvested zones.
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    IMPACT OF HUMAN EXPLOITATION ON POPULATIONS OF THE INTERTIDAL SOUTHERN BULL-KELP DURVILLAEA-ANTARCTICA (PHAEOPHYTA, DURVILLEALES) IN CENTRAL CHILE
    (1990) BUSTAMANTE, RH; CASTILLA, JC
    The effect of small-scale harvesting on populations of Durvillaea antarctica (Chamisso) was studied at four localities in central Chile. Density, standing crop and mean individual size were compared between populations protected from harvesting and those subjected to repeated cropping. Populations on islands, where access by collectors is restricted, were also assessed. Populations of D. antarctica at harvested mainland sites did not differ in abundance (density and standing crop) or mean size. At non-harvested sites standing crops were twice as high as at harvested sites. However, plant density at harvested sites was double that at non-harvested sites. Mean algae size at harvested sites was significantly smaller than at non-harvested sites, because collectors select the largest individuals, usually those with a holdfast diameter of greater than 4 cm. A significant positive correlation was found between wet biomasses present on the islands and those at adjacent harvested and non-harvested mainland sites. Availability of potential space for settlement was also correlated with the density of algae, both on the mainland and on islands. Islands appear to act as seeding grounds or refugial areas, supplying recruits to the adjacent mainland sites. Differences in abundance of D. antarctica between the different localities could therefore be explained by the level of exploitation and by the local geomorphology, particularly the presence or absence of nearshore islands.