Browsing by Author "CASTILLA, JC"

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    A NEW SPECIES OF POLYCHAETE, SCOLELEPIS-ANAKENAE (POLYCHAETA, SPIONIDAE) FROM EASTER-ISLAND, SOUTH-PACIFIC OCEAN, WITH ECOLOGICAL COMMENTS
    (1988) ROZBACZYLO, N; CASTILLA, JC
    A new species of Spionidae, Scolelepis anakenae from Easter Island, is described. Scolelepis anakenae, which closely resembles Scolelepis chilensis (Hartmann-Schroder) from the coast of Chile was the only polychaete species found in sand at Anakena beach during a macrofaunistic study. Comments about its distribution and population density in the intertidal zone are included.
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    BARNACLE WALLS AS MEDIATORS OF INTERTIDAL MUSSEL RECRUITMENT - EFFECTS OF PATCH SIZE ON THE UTILIZATION OF SPACE
    (1990) NAVARRETE, SA; CASTILLA, JC
    Recruitment of the competitively dominant mussel Perumytilus purpuratus to the mid rocky intertidal zone in central Chile depends upon the presence of recruitment-mediators such as mussel clumps, filamentous algae or barnacle shells. The relationship between the lateral walls of adult barnacles and the recruitment of P. purpuratus was investigated in a semi-sheltered rocky habitat at Las Cruces, central Chile. Changes in number of individuals and percent cover of sessile species were recorded for 8 mo (January to September 1988) in different sized patches of bare rock. All patches were surrounded by barnacle beds. Throughout the study, P. purpuratus recruited only on the walls of adult barnacles that formed the patch borders, and never on bare rock. Conversely barnacles recruited directly on the bare surface of cleared patches. Regressions of numbers of individuals in relation to patch area showed that mussel recruits outnumbered those of barnacles in patches smaller than 35.5 cm2. Above this critical patch area, the number of barnacle recruits was progressively larger than that of mussels. The area of barnacle walls suitable for mussel recruitment increases linearly with increasing patch perimeter, while the area suitable for barnacle recruitment is a function of patch area. The number of recruits was related to the substratum availability in different patch sizes, suggesting that recruitment of barnacles and mussels is not limited by larval abundance. The probability of mussels monopolarizing the patches was higher in small than in large patches; the chance for barnacles to monopolize large patches increased with increasing size of patch. Consequently a barnacle-dominated substratum may change to a mussel-dominated one depending upon the relative abundances of small and large patches. A barnacle bed disrupted in several small patches will provide more substratum for mussel recruitment than if only few large patches are produced. Possible effects of patch and predator sizes on intertidal community structure are discussed.
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    BODY-SIZE, POPULATION-DENSITY, AND THE ENERGETIC EQUIVALENCE RULE
    (1995) MARQUET, PA; NAVARRETE, SA; CASTILLA, JC
    1. We critically evaluated the Energetic Equivalence Rule (EER) with regard to its underlying theoretical framework, its dependence of a particular relationship between population density and body size, and the way it is calculated.
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    COMPARATIVE ECOLOGY OF LESSONIA-NIGRESCENS AND DURVILLAEA-ANTARCTICA (PHAEOPHYTA) IN CENTRAL CHILE
    (1980) SANTELICES, B; CASTILLA, JC; CANCINO, J; SCHMIEDE, P
    The L. nigrescens-D. antarctica belt is the most conspicuous feature of the intertidal-subtidal boundary in central Chile, with L. nigrescens attaining larger cover and biomass values than D. antarctica. Human predation of the otherwise competitively dominant D. antarctica has been suggested as accounting for its scarcity. Testing of this hypothesis included field studies of species distribution in places with and without human accessibility and various degrees of wave impact, comparative morphometric and population studies, evaluation of the ecologic role of the limpet-kelp association and comparative measurements of growth, reproduction and survival capacity. Results indicate that L. nigrescens and D. antarctica have morphologies typically adapted to habitats with different wave shock. Contrary to previous predictions, L. nigrescens appears as a plant better adapted for places with strong wave impact, which are the most common in central Chile. Complete space monopolization by L. nigrescens is prevented by a series of adaptations of D. antarctica. Certain morphological forms of this species are less affected by wave action, allowing a population stock to persist even at the most exposed places. Boring into algal holdfasts by invertebrates weakens the mechanical resistance of old, eroded plants providing open space where juveniles of either species could settle. D. antarctica seems to take greater advantage of this primary space by a fugitive life history. Finally, the survival of D. antarctica increases if attached to the top of L. nigrescens holdfasts. The result of the interaction between these 2 brown algae depends on the degree of water impact. In sheltered habitats competitive displacement of L. nigrescens could occur but it is unlikely to be a continuous process. In exposed habitats D. antarctica is constantly removed by water movement, but persists because of a higher colonization rate.
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    DISTRIBUTIONAL PATTERNS AND DIETS OF 4 SPECIES OF SEA-URCHINS IN GIANT-KELP FOREST (MACROCYSTIS-PYRIFERA) OF PURETO-TORO, NAVARINO ISLAND, CHILE
    (1984) VASQUEZ, JA; CASTILLA, JC; SANTELICES, B
    The distribution pattern of microhabitat and diet was studied in 4 spp. of sea urchins (Loxechinus albus, Pseudechinus magellanicus, Arbacia dufresnei, Austrocidaris canaliculata) in a forest of M. pyrifera in southern Chile. There is no overlap in space utilization (microhabitat) except for the species pair P. magellanicus-A. canaliculata. All 4 spp. of sea urchins feed on M. pyrifera in different percentages; this results in a high diet overlap in at least 3 of them; this resource does not appear to be limiting. Neither competition among adults nor predation on adults appears to be a key factor in regulating the present population desenties of the 4 spp. of sea urchins in the habitat studied. Differences in intensity of water movement, correlated with bathymetric distribution, regulate population density, size of test and biomass in these 4 spp.
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    EARTHQUAKE-CAUSED COASTAL UPLIFT AND ITS EFFECTS ON ROCKY INTERTIDAL KELP COMMUNITIES
    (1988) CASTILLA, JC
    The coastal uplift (approximately 40 to 60 centimeters) associated with the Chilean earthquake of 3 March 1985 caused extensive mortality of intertidal organisms at the Estacion Costera de Investigaciones Marinas, Las Cruces. The kelp belt of the laminarian Lessonia nigrescens was particularly affected. Most of the primary space liberated at the upper border of this belt was invaded by species of barnacles, which showed an opportunistic colonization strategy. Drastic modifications in the environment such as coastal uplift, subsidence, or the effects of the El Nino phenomenon are characteristic of the southern Pacific. Modifications in the marine ecosystem that generate catastrophic and widespread mortalities of intertidal organisms can affect species composition, diversity, or local biogeography.
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    ECOLOGICAL CONSEQUENCES OF COSEISMIC UPLIFT ON THE INTERTIDAL KELP BELTS OF LESSONIA-NIGRESCENS IN CENTRAL CHILE
    (1990) CASTILLA, JC; OLIVA, D
    Coseismic uplift from the Chilean earthquake of 3 March 1985 caused changes in the biomass and vertical zonation of rocky intertidal organisms at four sites along 150 km of the central Chilean coast. The 11-60 cm uplift caused widespread mortality mainly of the dominant intertidal kelp Lessonia nigrescens, reducing its biomass in the upper part of its pre-earthquake range and altering the vertical zonation. The L. nigrescens belt shrank from the top by about 0.5-1 m within 1 year of the shocks, then expanded downward by about 1 m. An important part of the primary space liberated at the pre-earthquake upper border of Lessonia was invaded by the barnacles Chthamalus scabrosus and Fehlius cirratus. None of the foregoing changes occurred at two control sites located outside the shock area. The ecological effects of these recurrent sudden and drastic environmental processes on rocky intertidal communities include the liberation of primary space, enhancement of mosaic areas and modification of the vertical zonation of competitively dominant organisms.
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    EMERSION BEHAVIOR AND FORAGING ECOLOGY OF THE COMMON CHILEAN CLINGFISH SICYASES-SANGUINEUS (PISCES, GOBIESOCIDAE)
    (1988) CANCINO, JM; CASTILLA, JC
    The present study is the first to correlate information on emersion behaviour and foraging ecology of Sicyases sanguineus, a common clingfish of the Chilean coast. Individuals smaller than 15 cm in total length were frequently found at the highest points in the inter-tidal zone and consumed inter-tidal animals and seaweeds. Fish larger than 23 cm were infrequently observed emersed in the lower inter-tidal zone, but were collected sub-tidally by divers. These large clingfish ate mainly benthic animals occurring in the low inter-tidal and sub-tidal zones. Size-dependent factors, dessication and wave impact restrict the area of action of S. sanguineus to certain areas of the rock inter-tidal and shallow sub-tidal zone. However, the fish can be locally very abundant, consuming a great diversity of prey items including both direct primary space users and mobile animals able to affect community structure through grazing. We argue, therefore, that S. sanguineus may be important in structuring communities in some areas of the rocky inter-tidal and shallow sub-tidal zones of Central Chile.
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    ENVIRONMENTAL-IMPACT IN SANDY BEACHES OF COPPER MINE TAILINGS AT CHANARAL, CHILE
    (1983) CASTILLA, JC
    Since 1938, untreated Cu mine tailings of Potrerillos and El Salvador had been disposed into the sea at Chanaral, Chile (26.degree.21'' latitude south, 70.degree.42'' longitude west). Over 220 .times. 106 tons of sediments had been dumped. This pollution caused drastic geomorpholigcal changes in the .apprx. 16 km contaminated area. The occurrence of new artificial beaches and modification of coastal contours were reported. Sandy beach macrofauna monitoring (1975-1982) demonstrated a progressive lowering of density and biomass in those communities affected by Cu mine tailings.
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    FORAGING ACTIVITIES OF CHILEAN INTERTIDAL CRABS ACANTHOCYCLUS-GAYI MILNE-EDWARDS ET LUCAS AND ACANTHOCYCLUS-HASSLERI RATHBUN
    (1988) NAVARRETE, SA; CASTILLA, JC
    Foraging activities of the Chilean intertidal carnivorous crabs Acanthocyclus gayi Milne-Edwards et Lucas and A. hassleri Rathbun were studied in the laboratory. These crabs are morphologically similar and coexist in the intertidal zone, feeding mainly on mussels, barnacles, and gastropods. The consumption rates of A. gayi were generally higher than those of A. hassleri, when feeding on mussels and limpets, but similar, when feeding on barnacles. Both species foraged more actively underwater. Out of water, foraging activity was greater at night than during the day. Both crab species preferred the smallest sizes of the mussel Perumytilus purpuratus Lamarck, well below the maximum size they can handle. In both species, the critical size of mussels increased linearly with crab size. A. hassleri was able to handle larger mussels than its congenergic species, but when > 15 mm carapace width both crabs could handle even the largest mussels found in the field. A. gayi strongly preferred the mussel Semimytilus algosus (Gould), which is much less abundant in the intertidal than P. purpuratus, and the least preferred item was the barnacle Jehlius cirratus (Darwin), one of the most abundant organisms in the field. In paired experiments, A. hassleri showed the same preference order as A. gayi, and when all prey species were available, A. hassleri preferred J. cirratus over any other prey. Both crabs used similar techniques to handle, open, and eat their prey. Crabs adopted any of six different techniques to handle mussels, depending largely on the crab-prey size ratio. For handling limpets and barnacles, the crabs used two different techniques, which also depended on crab and prey sizes. In conclusion, the two crab species are similar, not only morphologically, but also in their trophic behaviour. Factors enabling the coexistence of both species in the intertidal zone need further study. The results are compared with those obtained for other crab species and the possible ecological role of Chilean crabs in the community is discussed.
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    FORAGING, ACTIVITY BUDGET, AND SOCIAL-BEHAVIOR OF THE SOUTH-AMERICAN MARINE OTTER LUTRA-FELINA (MOLINA 1782)
    (1989) OSTFELD, RS; EBENSPERGER, L; KLOSTERMAN, LL; CASTILLA, JC
    The foraging behavior and activity budgets of marine otters were studied at three sites spanning -1800 km along the Chilean coast. A total of 1569 foraging dives were observed, of which 481 (30.7%) were successful (prey obtained). Altogether, the diet consisted of crabs (69.8%), fishes (19.9%), shrimp (6.4%), and molluscs (3.9%). Among the three sites, success rate, diet, dive time, activity budget, and possibly social structure differed distinctly. Behavior of otters at the central site was characterized by a high percentage of time spent foraging, low success rate, and consumption of large prey. At the southern site, otters specialized on crabs, lacked crepuscular activity, and spent a low percentage of time in social groups. Otters at the northern site were intermediate in most behavioral attributes. The composition of the diet, as well as several aspects of foraging behavior, are in this species intermediate between those of closely related river otters (Lutra spp.) and more distantly related sea otters (Enhydra lutris). The social organization seemed to consist mainly of monogamous family groups, and was not convergent upon that of sea otters, which are polygnous.
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    GALLERIES OF THE CRABS ACANTHOCYCLUS UNDER INTERTIDAL MUSSEL BEDS - THEIR EFFECTS ON THE USE OF PRIMARY SUBSTRATUM
    (1989) CASTILLA, JC; LUXORO, C; NAVARRETE, SA
    The mid rocky intertidal of Cachagua, like many other rocky sites in central Chile, is dominated by beds of the mussel Perumytilus purpuratus. Under these mussel beds the predatory crabs Acanthocyclus gayi and A. hassleri build separated bind-ending galleries whose floor is the rock and the roof is the mussel bed. Samples of 1 m2 of Perumytilus beds (100% cover) showed that the surface area of crab galleries ranged between 17.4% and 34.7% of the total area, and that 80% of the crabs were A. hassleri. In 130 of the 157 galleries analyzed, one or two conspecific crabs were found. In the remainder, up to six crabs were found together. Comparisons between the floor of crab galleries and similar rocky areas under the mussel bed, but without galleries (controls), showed that both density and cover of Balanus flosculus, Phymactis clematis and bryozoans were significantly higher in galleries. Similarly, the total number of species was greater on the floor of the galleries than in the controls. Although from outward appearances the cover of P. purpuratus remained at 100%, crab galleries allowed more sessile species to occupy the mid intertidal fringe. This occurs because of the introduction of species typical of the lower intertidal, which would otherwise be excluded by mussels.
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    GROWTH, MORTALITY AND RECRUITMENT OF THE YELLOW CLAM MESODESMA-MACTROIDES ON URUGUAYAN BEACHES
    (1992) DEFEO, O; ORTIZ, E; CASTILLA, JC
    We studied some aspects of the population dynamics of the yellow clam Mesodesma mactroides (Deshayes, 1854) which inhabits the eastern sandy beaches of Uruguay. Observations were made from March 1983 through March 1985 (harvesting season), and additional data from January 1988 to December 1989 (closed season) were also included in the analyses. Parameters of growth and mortality were estimated by methods that make use of age or length information. An age/length relationship was constructed by counting growth rings. Results were consistent with those obtained with modal class progression analysis and other length/frequency methods. The growth curve obtained from the age/length relationship did not account for seasonality in growth rate, and a seasonal growth model explained growth oscillations in a better way. The instantaneous coefficient of natural mortality (M) estimated for the closed season was 1.64, whereas an increase in fishing mortality (F) was observed during 1984. Age composition did not change during the 2 yr of study, and the first 6 mm class accounted for over 50% of the population. The main contribution of recruits was observed between late summer and early fall (February to April), and the recruitment pattern suggested one main settlement period per year. Growth and recruitment success appeared to be regulated by density-dependence processes. Some implications for management are considered in this context. Methodological aspects concerning the reliability of empirical equations and programs for estimating growth and mortality are discussed.
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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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    HUMAN EXCLUSION FROM THE ROCKY INTERTIDAL ZONE OF CENTRAL CHILE - THE EFFECTS ON CONCHOLEPAS CONCHOLEPAS (GASTROPODA)
    (1985) CASTILLA, JC; DURAN, LR
    The ecological role played by man as a top predator in a rocky intertidal environment of central Chile was studied. Human exclusion from a rocky intertidal stretch of coast (non-harvested area) at punta El Lacho, for nearly two years, resulted in a substantial density increase of the economically important high trophic level predator muricid Concholepas concholepas. This was followed by a dramatic decline in the cover of the competitive dominant intertidal mussel Perumytilus purpuratus. According to current ecological theory the removal of the competitively superior primary space dominant species led to a pattern of increasing species diversity. We conclude that in the absence of human interference C. concholepas plays the role of a key species in central Chile rocky intertidal environments. We suggest that the interpretation of the structure and dynamics of intertidal landscapes should include the key role played by man. Comparison of monitoring programs between intertidal areas with and without human interference will prove critical to our understanding of such environments.
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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.
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    MARINE ENVIRONMENTAL-IMPACT DUE TO MINING ACTIVITIES OF EL-SALVADOR COPPER MINE, CHILE
    (1978) CASTILLA, JC; NEALLER, E
    Marine environmental impact as a result of Cu mine tailing dumping in the sea is studied at Chanaral (North Chile). These dumpings, from the Cu mine El Salvador, hindered harbor activities, caused geomorphological coastal modifications and seriously affected marine coastal ecosystems and recreational activities. At the old dumping site, Chanaral Bay (1938-1974), nearly 150 million tons of fine sediments were accumulated. Tailing discharges at the new dumping site, Caleta Palito, about 8 km north of Chanaral Bay are accumulating approximately at the rate of 25,000 tons of fine sediments/day, plus unknown quantities of chemicals (Cu, As, CN-). From Jan., 1975-July, 1976, this site received over 13 million tons of sediments, which caused deterioration of the marine coastal environment, reduction in light penetration and high mortalities among marine invertebrates, fishes and algae.