UCN-CEAZA
Effects of isolation and fishing on the marine ecosystems of Easter Island and Salas y Gómez, Chile.
Friedlander, A., Ballesteros, E., Beets, J., Berkenpas, E., Gaymer, C., Gorny, M., & Sala, E.
An expedition to Salas y Gómez and Easter islands was conducted to develop a comprehensive baseline of the nearshore marine ecosystem, to survey seamounts of the recently created Motu Motiro Hiva Marine Park (MMHMP) – a no-take marine reserve of 150 000 km2 – and to compare these results with Easter Island where the marine ecosystem is similar but has no marine protection.
Live coral cover was surprisingly high at both Easter Island (53%) and Salas y Gómez (44%), especially considering their sub-tropical location, high wave energy environments, and geographic isolation.
Endemic and regionally-endemic species comprised 77% of the fish abundance at Easter Island and 73% at Salas y Gómez. Fish biomass at Salas y Gómez was relatively high (1.2 t ha-1) and included a large proportion of apex predators (43%), whereas at Easter Island it was almost three times lower (0.45 t ha-1) with large predators accounting for less than 2% of the biomass, despite good habitat quality.
The large cohort of small sharks and the absence of larger sharks at Salas y Gómez suggest mesopredator release consistent with recent shark fishing. The fish fauna at the seamounts between Easter Island and Salas y Gómez, outside of MMHMP, harboured 46% endemic species, including a new species of damselfish (Chromis sp. nov.) and probably a new species of Chimaera (Hydrolagus). Numerous seamounts adjacent to Salas y Gómez are currently not included in the MMHMP.
This expedition highlights the high biodiversity value of this remote part of the Pacific owing to the uniqueness (endemicity) of the fauna, large apex predator biomass, and geographic isolation.
Año: 2013
Palabras claves: Coral; biodiversity; no-take marine reserve; algae; fish; fishing.
Referencia APA: Friedlander, A., Ballesteros, E., Beets, J., Berkenpas, E., Gaymer, C., Gorny, M., & Sala, E. (2013). Effects of isolation and fishing on the marine ecosystems of Easter Island and Salas y Gómez, Chile. Aquatic Conserv: Mar. Freshw. Ecosyst., 23(4), 515-531.
Demography and feeding behavior of the kelp crab Taliepus marginatus in subtidal habitats dominated by the kelps Macrocystis pyrifera or Lessonia trabeculata.
Jofré Madariaga, D., Ortiz, M., & Thiel, M.
We studied the population and feeding ecology of the kelp crab Taliepus marginatus in subtidal kelp forests dominated by either of two morphologically different kelp species (Macrocystis pyrifera or Lessonia trabeculata) in northern Chile. The sizes and abundances of T. marginatus differed between the two kelp habitats. Kelp crabs were more abundant in the M. pyrifera forest than in the L. trabeculata forest. Size-frequency distributions showed that juvenile and immature crabs were more common in the M. pyrifera forest than in the L. trabeculata forest, where reproductive adults predominated. The smaller crabs in the M. pyrifera habitat also consumed a higher proportion of kelp tissues than the larger crabs in the L. trabeculata habitat, which had a higher proportion of animal food in their diet. In both kelp forests, individuals of T. marginatus showed a similar pattern of nocturnal feeding over a 24-h period, consuming more food at night than during the day. The more complex and dense forests of M. pyrifera appear to present better nursery habitats for juvenile kelp crabs than the more open and less dense forests dominated by L. trabeculata. These results suggest that the role of the two kelp habitats for T. marginatus varies during the life cycle of the kelp crabs, with M. pyrifera tending to have nursery function and L. trabeculata being more suitable as a reproductive habitat.
Año: 2013
Palabras claves: Habitat use; nursery habitat; reproductive habitat; diet.
Referencia APA: Jofré Madariaga, D., Ortiz, M., & Thiel, M. (2013). Demography and feeding behavior of the kelp crab Taliepus marginatus in subtidal habitats dominated by the kelps Macrocystis pyrifera or Lessonia trabeculata. Invertebrate Biology, 132(2), 133-144.
Sea urchin Tetrapygus niger distribution on elevated surfaces represents a strategy for avoiding predatory sea stars
Urriago, J., Himmelman, J., & Gaymer, C.
We ran field experiments to examine whether the micro-distribution of the sea urchin Tetrapygus niger on elevated surfaces represents a strategy for limiting predation by the sea stars Heliaster helianthus and Meyenaster gelatinosus. Several lines of evidence supported this hypothesis. (1) A survey of the distribution of the urchin and the 2 sea stars showed that urchins occur mainly on elevated surfaces, and sea stars on low surfaces. (2) In trials involving simulated attacks, the time needed by the urchin to sever contact with the sea stars was 48% less on elevated surfaces than on the bottom. (3) In trials involving sustained simulated attacks (high predatory risk) the urchins could detach themselves from the elevated surfaces to avoid being eaten. Finally, tethering experiments indicated that the urchin had a higher survival rate on elevated than low surfaces. Our observations indicate that M. gelatinosus represents a stronger predatory threat to T. niger than H. helianthus.
Año: 2012
Palabras claves: Tetrapygus niger · Heliaster helianthus · Meyenaster gelatinosus · Predator−prey interactions · Aggregation · Distribution · Tethering
Referencia APA: Urriago, J., Himmelman, J., & Gaymer, C. (2012). Sea urchin Tetrapygus niger distribution on elevated surfaces represents a strategy for avoiding predatory sea stars. Marine Ecology Progress Series, 444, 85-95.
Effects of patch size and position above the substratum during early succession of subtidal soft-bottom communities.
Pacheco, A., Thiel, M., Oliva, M., & Riascos, J.
Early macrobenthos succession in small, disturbed patches on subtidal soft bottoms is facilitated by the arrival of post-larval colonizers, in particular by active and passive dispersers along the seafloor or through the water column. Using a field experiment at two contrasting sites (protected vs. exposed to wave action), we evaluated the role of (a) active and passive dispersal through the water column and (b) the influence of small-scale spatial variability during succession of subtidal macrobenthic communities in northern Chile. Containers of two sizes (surface area: small—0.12 m2 and large—0.28 m2) at two positions above the natural substratum (height: low—3 cm and high—26 cm) were filled with defaunated sediment, installed at two sandy sublittoral sites (7–9 m water depth) and sampled after 7, 15, 30, 60 and 90 days, together with the natural bottom sediment. The experiment took place during austral fall (from late March to early July 2010), when both larval and post-larval stages are abundant. At the exposed site, early succession was driven by similar proportions of active and passive dispersers. A sequence from early, late and reference communities was also evident, but container position and size affected the proportional abundance of dispersal types. At the protected site, the successional process started with abundant colonization of active dispersers, but toward the end of the experiment, the proportion of swimmer/crawlers increased, thus resembling the dispersal types found in the natural community. At this site, the position above the sediment affected the proportional abundance of dispersal types, but patch size had no effect. This study highlights that macrobenthic post-larvae can reach at least 26 cm high above the bottom (actively or passively, depending on site exposure), thus playing an important role during early succession of sublittoral soft bottoms. The active or passive use of the sediment–water interphase may also play an important role in the connectivity of benthic populations and in the recovery after large-scale disturbances of sublittoral habitats.
Año: 2012
Palabras claves: Colonization, Disturbance, Macrobenthos, Size effects, Recruitment, Active and passive dispersal, Humboldt, Current, System.
Referencia APA: Pacheco, A., Thiel, M., Oliva, M., & Riascos, J. (2012). Effects of patch size and position above the substratum during early succession of subtidal soft-bottom communities. Helgoland Marine Research, 66(4), 523-536.
Effects of predation and habitat structure on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Caridea) on temperate rocky reefs.
Ory, N., Dudgeon, D., Dumont, C., Miranda, L., & Thiel, M.
Human disturbances, such as overfishing, may disrupt predator–prey interactions and modify food webs. Underwater surveys were carried out at six shallow-water reef barrens in temperate waters of northern-central Chile from October to December 2010 to describe the effects of predation, habitat complexity (low, medium and high) and refuge availability on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Rhynchocinetidae), an important mesoconsumer on subtidal hard substrata. Three sites were within managed (restricted access) areas for fishermen, and three were unmanaged (open-access). Field observations and tethering experiments were conducted to examine the relationship between fish and shrimp abundances, and the relative predation rates on shrimps. Direct effects of predation on R. typus body-size distribution were examined from shrimps collected in the field and fish stomachs. The presence and the abundance of R. typus increased with habitat reef complexity and refuge availability. Shrimp abundance was negatively related to fish abundance in managed areas, but not in open-access areas, where shrimp densities were the highest. Also, predation rates and body-size distribution of shrimps were unrelated, although fish consumed more large shrimps than should be expected from their distribution in the field. R. typus occurred most often in shelters with wide openings, offering limited protection against predators, but providing potential aggregation sites for shrimps. Overall, direct effects of predation on shrimp densities and population structure were weak, but indirect effects on shrimp distribution within reefs appear to have been mediated through behavioural responses. Our study highlights the need to assess both numerical and behavioural responses of prey to determine the effects of predator loss on mesoconsumer populations.
Año: 2012
Palabras claves:
Referencia APA: Ory, N., Dudgeon, D., Dumont, C., Miranda, L., & Thiel, M. (2012). Effects of predation and habitat structure on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Caridea) on temperate rocky reefs. Marine Biology, 159(9), 2075-2089.
Floating kelps in Patagonian Fjords: an important vehicle for rafting invertebrates and its relevance for biogeography.
Wichmann, C., Hinojosa, I., & Thiel, M.
Floating macroalgae are common dispersal vehicles for associated benthic invertebrates. In order to investigate the importance of kelp rafts for species dispersal in the Patagonian Fjord Region (PFR), the abundance and distribution pattern of floating kelps (Macrocystis pyrifera, Durvillaea antarctica) and of the invertebrate fauna associated with M. pyrifera were evaluated during austral spring of 2002–2005, 2008 and 2010. In the southernmost Magellan Region (MR), benthic M. pyrifera were additionally sampled to compare the community structures in both conditions. Floating kelps were abundant throughout the entire PFR, harbouring a diverse and abundant invertebrate fauna. The density of floating kelps increased towards the south. In the MR, a loss of species was observed between benthic and floating condition (e.g. decapods, echinoderms, several peracarid species), but a high diversity of organisms from all major phyla were observed on rafts. Throughout the PFR, the predominant rafting species belonged to the peracarids, molluscs and annelids, but the community composition differed between floating samples from the northern and southern zones of the PFR. Relative abundances of peracarids were higher in northern zones, whereas molluscs and annelids dominated in the southern areas. Species of the peracarid genera Peramphithoe, Gondogeneia, Bircenna and Limnoria were shared between all areas. The results suggest that kelp rafts not only contribute to local population connectivity in the PFR, but could also be an important dispersal vehicle for rafting species along the PFR in north–south direction, crossing the biogeographic boundary around Taitao Peninsula. Furthermore, the MR appears to be an important stepping stone for species dispersal via kelp rafting in the subantarctic region.
Año: 2012
Palabras claves:
Referencia APA: Wichmann, C., Hinojosa, I., & Thiel, M. (2012). Floating kelps in Patagonian Fjords: an important vehicle for rafting invertebrates and its relevance for biogeography. Marine Biology, 159(9), 2035-2049.
Reproductive biology of two species of squat lobsters – female receptivity and interbrood intervals.
Espinoza-Fuenzalida, N., Acuña, E., Hinojosa, I., & Thiel, M.
The reproductive biology of many species of anomuran crabs is only poorly known. Herein we studied the reproductive biology of two species of squat lobsters, Cervimunida johni Porter, 1903 and Pleuroncodes monodon (H. Milne Edwards, 1837), which are target of a trawl fishery operating on the continental margin along the Chilean coast. During the reproductive period (May-November) we maintained squat lobsters in the laboratory to examine whether mating is related to the reproductive molt of the female and to determine the interbrood interval between successive broods. In both species females mated during the intermolt period. Females became receptive shortly after having released larvae from a previous brood, when they formed pairs with males. The interbrood interval (from larval release until having a subsequent brood) lasted <72<72 hour in the majority of female C. johni, but was longer in P. monodon, where most females took 72-144 hours before producing a new brood. Despite longer interbrood intervals, copulatory mate-guarding was substantially shorter in P. monodon than in C. johni. These differences in reproductive behavior might be due to differences in the general biology of the two species, including mobility and intraspecific aggression. Mating during the intermolt period may have several advantages, namely reducing the risk of cannibalism and energy costs of molting during the reproductive season.
Año: 2012
Palabras claves: female receptivity, mating, reproduction, squat lobsters, trawl fishery.
Referencia APA: Espinoza-Fuenzalida, N., Acuña, E., Hinojosa, I., & Thiel, M. (2012). Reproductive biology of two species of squat lobsters – female receptivity and interbrood intervals. Journal Of Crustacean Biology, 32(4), 565-574
Microplastics in the Marine Environment: A Review of the Methods Used for Identification and Quantification.
Hidalgo-Ruz, V., Gutow, L., Thompson, R., & Thiel, M.
This review of 68 studies compares the methodologies used for the identification and quantification of microplastics from the marine environment. Three main sampling strategies were identified: selective, volume-reduced, and bulk sampling. Most sediment samples came from sandy beaches at the high tide line, and most seawater samples were taken at the sea surface using neuston nets. Four steps were distinguished during sample processing: density separation, filtration, sieving, and visual sorting of microplastics. Visual sorting was one of the most commonly used methods for the identification of microplastics (using type, shape, degradation stage, and color as criteria). Chemical and physical characteristics (e.g., specific density) were also used. The most reliable method to identify the chemical composition of microplastics is by infrared spectroscopy. Most studies reported that plastic fragments were polyethylene and polypropylene polymers. Units commonly used for abundance estimates are “items per m2” for sediment and sea surface studies and “items per m3” for water column studies. Mesh size of sieves and filters used during sampling or sample processing influence abundance estimates. Most studies reported two main size ranges of microplastics: (i) 500 μm–5 mm, which are retained by a 500 μm sieve/net, and (ii) 1–500 μm, or fractions thereof that are retained on filters. We recommend that future programs of monitoring continue to distinguish these size fractions, but we suggest standardized sampling procedures which allow the spatiotemporal comparison of microplastic abundance across marine environments.
Año: 2012
Palabras claves:
Referencia APA: Hidalgo-Ruz, V., Gutow, L., Thompson, R., & Thiel, M. (2012). Microplastics in the Marine Environment: A Review of the Methods Used for Identification and Quantification. Environmental Science & Technology, 46(6), 3060-3075.
Plasticity in feeding selectivity and trophic structure of kelp forest associated fishes from northern Chile.
Pérez-Matus, A., Pledger, S., Díaz, F., Ferry, L., & Vásquez, J.
One of the primary ways in which species interact with their environment is through foraging; thereby directly consuming some fraction of their surrounding habitat. The habitat itself, in turn, may dictate the types of foraging opportunities that are available to the inhabitants. To investigate the relationship between habitat availability and diet composition of habitat-associated fishes, we estimated the relative abundance of the potential sessile and mobile prey items and the diet of the fish species assemblage associated to kelp forest. Specifically, diet and feeding selectivity of the kelp-forest associated fish assemblage were determined by calculating Manly's alpha selectivity index. We determined the diet of kelp forest associated fishes and their foraging behavior by comparing prey availability with those items present in the stomachs of fishes captured by gill net and spear gun. We calculated the degree of dietary overlap among fishes from four locations along the northern coast of Chile. Results indicate that utilization of prey by predators is predominantly affected by potential prey availability. With the exception of the two carnivorous species such as Pinguipes chilensis (Valenciennes, 1883) and Paralabrax humeralis (Cuvier & Valenciennes, 1828), whose diet did not change among sites, all other kelp-associated fishes changed their dietary habitats to consistent with the availability of local resources. Benthic resources changed among the different study sites, which led to differing diets even in the same species from different locations. Eleven of the 12 kelp forest fishes also showed some selectively for benthic prey. We conclude that the ability of fishes to be plastic in their feeding preference and, therefore, partition the benthic resources may set adaptations to co-exist in a dynamic environment such as kelp forest.
Año: 2012
Palabras claves: Chile, Manly α, predation, trophic guilds, understory.
Referencia APA: Pérez-Matus, A., Pledger, S., Díaz, F., Ferry, L., & Vásquez, J. (2012). Plasticity in feeding selectivity and trophic structure of kelp forest associated fishes from northern Chile. Rev. Chil. Hist. Nat., 85(1), 29-48.
Bioeconomic effect from the size selection in red abalone intensive culture Haliotis rufescens as a production strategy.
Pérez, E., Araya, A., Araneda, M., & Zúñiga, C.
The variability in growth is a common characteristic in mollusks breeding. Effects rising from the variability in the individual growth rate and the consequent dispersion of sizes in cultivation are important in financial terms. To manage this heterogeneity many firms use size selection, which can happen in two stages: toward the end of the stage of growing, or in the phase of growing of seeds. A bioeconomic model simulating the operation of a firm producing red abalone was implemented in spreadsheets. The firm produces 70 tons yearly. The model was structured in three sub-models. A biological sub-model detailed a batch’s dynamics, in terms of survival and growth, considering individual variation of size around a central value for each age. A technological sub-model described raw materials, the quantity of food and the energy required. Finally, the simulation model is completed with an economic integrated sub-model, where net present value is calculated considering income and costs over the time. Results of the alternative production strategies (with or without selection) are assessed according to: quantity of larvae and necessary spawners to reach the desired level of production; net present value (NPV) and necessary time to recover the investment. The number of larvae was approximately 17 millions larger for the case of the strategy of production with sizes selection and 73% more of available spawners is required for this larger amount of larvae. In the short term, the size-selection strategy increases the production costs at the initial time, compared with the strategy without selection. However, in the long term, this strategy generates greater NPV. The span for investment recovery was shorter for the case of the strategy with size selection and living product (nearly 2,140 days) than frozen (nearly 2,232 days); while without sizes selection a 15-year simulation showed the investment is not recovered. Finally, could be verified that size selection can be an interesting strategy to explore, since it improves the financial result, the same way other more expensive technological changes would.
Año: 2012
Palabras claves: Bioeconomic effect, Red abalone, Size selection, Strategy.
Referencia APA: Pérez, E., Araya, A., Araneda, M., & Zúñiga, C. (2012). Bioeconomic effect from the size selection in red abalone intensive culture Haliotis rufescens as a production strategy. Aquaculture International, 20(2), 333-345.
Estimating rat predation on Humboldt Penguin colonies in north-central Chile.
Simeone, A. & Luna-Jorquera, G.
Rats (Rattus spp.) are among the most successful alien predators brought to islands by humans and have had devastating impacts on numerous seabird populations, but studies demonstrating rates of consumption and ecological impacts on penguins are scarce and mostly based on anecdotal evidence. We investigated the effects of rat predation on Humboldt Penguins (Spheniscus humboldti) by simulating unattended clutches with domestic Chicken eggs. Experiments were independently set at two Humboldt Penguin colonies in north (Pájaros Island, 29°S) and central Chile (Algarrobo Island, 33°S). At both colonies, eggs were primarily predated by rats (Rattus rattus = 70.8 % at Pájaros and Rattus norvegicus = 52.6 % at Algarrobo), and secondarily by Kelp Gulls (Larus dominicanus = 9.7 % at Pájaros and 15.8 % at Algarrobo). Significantly more eggs were predated at night. At both colonies, rates of rat and gull predation were highest within the first 12 h. Our study constitutes the first quantification of rats as important alien predators at Humboldt Penguin colonies. We suggest that rat presence at Humboldt Penguin colonies coupled with events that can cause temporary nest abandonment, such as human perturbation and El Niño events, may impact on the species’ breeding success. Eradication of rats is suggested to improve the nesting habitat of this and other threatened and endemic seabird species in the region.
Año: 2012
Palabras claves: Introduced species, Island conservation, Nest attendance, Alien predation, RattusPenguins
Referencia APA: Simeone, A. & Luna-Jorquera, G. (2012). Estimating rat predation on Humboldt Penguin colonies in north-central Chile. J Ornithol, 153(4), 1079-1085.
Estimaciones de crecimiento de Haliotis rufescens en cautiverio en el norte de Chile.
Pérez E., Eduardo P. AU - Araya, AndreaTI.
El crecimiento en acuicultura es indicador directo de productividad,permite predecir el desarrollo del cultivo y la cosecha, afecta indirectamente el desempeño de variables tecnológicas y determina el tiempo necesario para obtener individuos de un tamaño específico, lo cual condiciona el beneficio económico de un cultivo. Estas condiciones requieren la toma de datos y descripción adecuada del crecimiento de la especie cultivada. En este trabajo se evalúan tres alternativas de ajuste de parámetros de crecimiento a partir de información recopilada en un centro de cultivo de abalón rojo Haliotis rufescens en Coquimbo, Chile, donde se midieron durante un año individuos de 1,4-4,3 años, por intervalos de tamaño de 15-25, 26-35, 36-45, 46-55 y 56-65mm de longitud. Para analizar la consistencia en la estimación de crecimiento, se utilizaron tres modelos: la ecuación de von Bertalanffy (ECVB), la versión con crecimiento estacionalizado de ECVB y el modelo generalizado de crecimiento de Schnute y Richards. Los tres modelos resultaron ser confiables para longitudes en edades de 1,4-4,3 años, y las curvas de ajuste pasan a través del centro de la nube de puntos. Coincide esta etapa con la fase de crecimiento exponencial de los organismos. Con un criterio estrictamente estadístico la ECVB en su versión estacionalizada es la más ajustada, por una menor suma de cuadrados. Dado que las extrapolaciones hacia edades mayores y menores resultan más exactas con el modelo generalizado de crecimiento, se concluye que éste representó mejor el crecimiento de H. rufescens en las condiciones locales de cultivo.
Año: 2012
Palabras claves:
Referencia APA: Pérez E., Eduardo P. AU - Araya, AndreaTI. (2012). Estimaciones de crecimiento de Haliotis rufescens en cautiverio en el norte de Chile. Interciencia, VL - 37IS - 2AB.