MOLLUSCA OF SOUTHERN CHILE 



143 



largest of which was about 100 m long and 5 m in depth. The age of 

 these middens is unknown. They correspond to the 'white middens' 

 described in the detailed survey of the archaeological sites of Isla 

 Traiguen by Curry (in press), consisting largely of intact shells and 

 fragments of Aulacomya atra, Choromytilus chorus, Venus antiqua 

 and the large barnacle Megabalanus psittacus, together with a few 

 shells of Concholepas concholepas, Crepidula dilatata, Trochita 

 trochiformis and Mulinia edulis. Gathering of molluscs by local 

 fishermen in the Estero Elefantes evidently continues, since we 

 found collections of fresh shells of Aulacomya atra, Choromytilus 

 chorus, Concholepas concholepas and Venus antiqua at several sites 

 on the shore, although this appears to be on a small scale. 



The exploitation of intertidal molluscs has implications not only 

 for conservation, but also for the general ecology of rocky shores. At 

 sites in central Chile, it has been demonstrated that where human 

 interference is prevented there are marked changes in zonation and 

 community structure. For example, Fissurella species become more 

 common when no longer gathered for food, grazing down the 

 previously abundant macroalgae such as Iridaea, and competing 

 with another grazer, Siphonaria lessonii (Moreno et ai, 1984; 

 Godoy & Moreno, 1989; Duarte et al., 1996). The large mussel 

 Choromytilus chorus is a prized species, so heavily exploited that it 

 has disappeared from intertidal habitats in much of its range ( Vi viani, 

 1979), yet in a marine reserve an intertidal population soon became 

 established (Moreno, 1 995). The most valuable, and perhaps vulner- 

 able, of the molluscs exploited in wild populations is Concholepas 

 concholepas. When intertidal collection is prevented populations on 

 the shore increase and include large adults that are elsewhere 

 restricted to the sublittoral zone; furthermore, the dense beds of 

 Perumytilus purpuratus and barnacles, both preyed upon by 

 Concholepas concholepas, become dramatically depleted (Castilla 

 &Duran, 1985; Moreno etai, 1986; Durante ai, 1987). Therefore, 

 in areas of the Chilean coast with significant human impact the 

 natural pattern of zonation is much altered. This emphasizes the 

 importance of conservation of relatively untouched coastlines such 

 as those of the Laguna San Rafael National Park and adjacent parts 

 of the Chonos Archipelago. 



ACKNOWLEDGEMENTS. The biodiversity research programme in the 

 Laguna San Rafael National Park, of which this project was a part, was 

 funded by a grant from the British Government's Darwin Initiative for the 

 Survival of Species. For logistic and administrative support we would like to 

 thank Sam Rose (Raleigh International, London), Keith Tuckwell and Graham 

 Hornsey (Raleigh International, Chile) and Sergio Herrera (Darwin Project, 

 CONAF). For their assistance and comradeship in the field we thank our 

 colleagues Maria Eliana Ramirez (MNHNS), Nick Evans (NHM) and David 

 John (NHM). This work would not have been possible without the enthusias- 

 tic participation of the team of Raleigh field staff and venturers who took part 

 in the Marine Survey of Expedition Chile 98A (January-February 1998); 

 staff members were Lee David, Kyle Lim. Jaime Plaza and Jill Webber; 

 venturers were Raimondo Benitez, Kate Bevins, Jo Brown, Nicholas 

 Edmeades, Stephen Fowler. Juliette Green, Joe Hoffman, Lee Joyce, Isla 

 McCleery, Peter Mackay-Lewis, Caroline Morgan and Clare Timmins. For 

 their advice on Chilean molluscs and assistance with the literature we are 

 most grateful to Pat Curry, Jerry Harasewych (Smithsonian Institution, 

 Washington, D.C.), Cristian Ituarte (Museo de La Plata, Argentina), Guido 

 Pastorino (Museo Argentino de Ciencias Naturales) and John Taylor (NHM). 

 For their comments on the manuscript we gratefully acknowledge Jim 

 McLean (Los Angeles County Museum of Natural History), Philippe Bouchet 

 (Museum National d'Histoire Naturelle. Paris) and David Jablonski (Univer- 

 sity of Chicago). Sarah Long (NHM) kindly identified the brachiopod. 

 Photography was by Harry Taylor (NHM). We acknowledge the support of 

 the Departamento de Investigacion y Desarrollo de la Universidad de Chile. 



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