DSpace Angular :: Browsing by Author "Fernandez, Miriam"

Browsing by Author "Fernandez, Miriam"

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Behavioral and chromatic dynamics describing mating interactions of the south American octopus Robsonella fontaniana (Cephalopoda: Octopodidae)
(2023) Cifuentes, Victor; Perez-Matus, Alejandro; Fernandez, Miriam; Ibanez, Christian M.; Carrasco, Sergio A.
Cephalopods are characterized by a substantial behavioral flexibility during reproductive interactions; however, for octopods rather few studies have provided empirical information on the mechanisms operating during male-male and male-female encounters. Using the small south American octopus Robsonella fontaniana (similar to 270 mm total length, similar to 70 mm mantle length), we evaluated the mating behavior based on octopuses from central Chile. Eighteen male-female and five male-male interactions were characterized in laboratory using ethograms divided into precopulatory and copulatory stages. Although subjects' interactions occurred in both treatments, extended mating periods (81-196 min) were only observed in the male-female trials, and specifically, in those involving larger octopuses (39% of the interactions; > 43 mm mantle length). During the precopulatory stage (4-20 min), different behavioral displays were evidenced in 57% of these male-female interactions, including: contact, exhibition of chromatic displays, swimming, and mounting. Larger pairs had longer copulation times, with a maximum of similar to 200 min in octopuses of 50 mm mantle length. The observed mating in adult male-female pairs and the practically null interaction between juveniles suggest that a maturity-conditional reproductive behavior (similar to 43 mm mantle length; similar to 38 gr), could be one of the mechanisms modulating mating interactions of R. fontaniana in the wild, potentially influencing aspects such as mate guarding behavior, possible sperm removal or sperm loading. (c) 2023 Elsevier B.V. All rights reserved.
Effects of harvesting on subtidal kelp forests (Lessonia trabeculata) in central Chile
(2022) Bularz, Bryan; Fernandez, Miriam; Subida, Maria Dulce; Wieters, Evie A.; Perez-Matus, Alejandro
The systematic degradation of marine ecosystems is a global phenomenon that has important and diverse consequences including biodiversity loss and reduced ecosystem service provisions. In temperate regions, subtidal kelp forests are dominant ecosystems in rocky coasts, subjected to the influence of local-scale stressors and regional environmental variation. For example, kelps within the Humboldt Current System are at risk of degradation from live-harvesting by fisheries. However, limited information exists regarding the long-term consequences of kelp harvesting, which, in turn, limits the ability to provide effective management and conservation efforts. Here, we examined the ecosystem-level consequences of the artisanal subtidal Lessonia trabeculata fishery along the coast of central Chile during a 2-year period, assessing (1) the change in adult and juvenile L. trabeculata density within harvested and nonharvested (control) plots (similar to 90 m(2)), (2) the impact of L. trabeculata harvesting on reef fish and macroinvertebrate assemblages, and (3) the change in density of the most abundant L. trabeculata-associated species. The experiment was conducted over a 2-year period, from December 2016 to May 2019. Approximately 90% of L. trabeculata was removed by an experienced kelp fisherman in experimental plots. After 2 years, L trabeculata and its associated community showed a lack of recovery in the harvested plots. Within these plots, the average abundance of the rock shrimp, Rhynchocinetes typus, and the herbivorous snail, Tegula tridentata, was greater than in nonharvested plots and the pattern persisted over the study period. The difference in abundance of associated species may be key to the (lack of) recovery of L. trabeculata forests. Our study highlights the impact of L. trabeculata harvesting on associated fauna; however, significant knowledge gaps remain regarding the capacity and time frame to reestablish the original biomass of L trabeculata, as well as its associated fauna. The management of L. trabeculata fisheries needs to account for ecosystem-wide impacts in order to better manage and protect vital coastal ecosystems.
EMBRYONIC DEVELOPMENT, FEEDING AND INTRACAPSULAR OXYGEN AVAILABILITY IN TROPHON GEVERSIANUS (GASTROPODA: MURICIDAE)
(OXFORD UNIV PRESS, 2011) Cumplido, Mariano; Pappalardo, Paula; Fernandez, Miriam; Averbuj, Andres; Bigatti, Gregorio
Large-scale patterns of encapsulated embryo development and causal factors determining developmental success in the marine environment have been relevant issues of research for decades. We studied the embryonic development and intracapsular oxygen availability of Trophon geversianus in egg capsules from northern Patagonia (Golfo Nuevo, Argentina). The intracapsular embryonic development had a mean duration of 112 days (at 12-14 degrees C). The initial number of eggs per capsule was 197 (mean diameter 270 mu m), but on average only four embryos per capsule reached the juvenile stage. Embryos fed on nurse eggs (which disintegrated spontaneously 48 h after oviposition). The sequence of intracapsular developmental stages was recorded from egg to hatching occurred at the crawling stage (mean shell length 2.8 mm). Maximum growth rate was observed at the 'veliger' stage, while nurse eggs were consumed. A decrease in embryo number was observed between prehatching and hatching. Cannibalism was recorded in an egg capsule containing a prehatching embryo, which showed signs of shell drilling by the accessory boring organ. Intracapsular oxygen availability decreased from 90% during the cleavage stage to 45% of air saturation in the final stages of development (at 13 degrees C). Abnormal embryos were recognized in egg capsules, probably associated with food competition or oxygen limitation.
Environmental DNA reveals temporal variation in mesophotic reefs of the Humboldt upwelling ecosystems of central Chile: Toward a baseline for biodiversity monitoring of unexplored marine habitats
(2024) Saenz-Agudelo, Pablo; Ramirez, Paula; Beldade, Ricardo; Campoy, Ana N.; Garmendia, Vladimir; Search, Francesca V.; Fernandez, Miriam; Wieters, Evie A.; Navarrete, Sergio A.; Landaeta, Mauricio F.; Perez-Matus, Alejandro
Temperate mesophotic reef ecosystems (TMREs) are among the least known marine habitats. Information on their diversity and ecology is geographically and temporally scarce, especially in highly productive large upwelling ecosystems. Lack of information remains an obstacle to understanding the importance of TMREs as habitats, biodiversity reservoirs and their connections with better-studied shallow reefs. Here, we use environmental DNA (eDNA) from water samples to characterize the community composition of TMREs on the central Chilean coast, generating the first baseline for monitoring the biodiversity of these habitats. We analyzed samples from two depths (30 and 60 m) over four seasons (spring, summer, autumn, and winter) and at two locations approximately 16 km apart. We used a panel of three metabarcodes, two that target all eukaryotes (18S rRNA and mitochondrial COI) and one specifically targeting fishes (16S rRNA). All panels combined encompassed eDNA assigned to 42 phyla, 90 classes, 237 orders, and 402 families. The highest family richness was found for the phyla Arthropoda, Bacillariophyta, and Chordata. Overall, family richness was similar between depths but decreased during summer, a pattern consistent at both locations. Our results indicate that the structure (composition) of the mesophotic communities varied predominantly with seasons. We analyzed further the better-resolved fish assemblage and compared eDNA with other visual methods at the same locations and depths. We recovered eDNA from 19 genera of fish, six of these have also been observed on towed underwater videos, while 13 were unique to eDNA. We discuss the potential drivers of seasonal differences in community composition and richness. Our results suggest that eDNA can provide valuable insights for monitoring TMRE communities but highlight the necessity of completing reference DNA databases available for this region.
Geographical Variation of Shell Thickness in the Mussel Perumytilus purpuratus Along the Southeast Pacific Coast
(2014) Briones, Carolina; Rivadeneira, Marcelo M.; Fernandez, Miriam; Guinez, Ricardo
At broad geographical scales, the variation in bivalve shell thickness can be modulated by environmental factors that vary with latitude, such as sea surface temperature (SST), seawater pH, or calcium carbonate availability. Mussels usually form multilayered beds, and shell thickness is also expected to be affected by density and layering due to intraspecific competition. In this work, we explored the geographical variation of shell thickness in the intertidal mussel Perumytilus purpuratus between 18 degrees and 42 degrees S along the southeastern Pacific coast. We tested the hypothesis that there was a positive relationship between shell thickness and SST, and then we explored other variables that could have an effect on thickness, such as density, number of layers, and others environmental variables (pH and calcite concentration). The expected positive linear relationship between shell thickness and sea surface temperature was not found, but when the other population variables were included in the analysis, an unexpected inverse SST-thickness relationships appeared as significant, probably because this species could be adapted to colder and more acid seawater as are those of the tips of South America. Thickness was also negatively affected by density, which was expected for a gregarious species showing high intraspecific competition. Finally, our results highlight the importance of including density and crowding effects when macroscale patterns are explored, particularly in gregarious species, since these patterns could also be modulated by density-dependent processes, which might then override latitudinal trends of shell thickness when they are not included in the analyses.
Influence of larval traits on dispersal and connectivity patterns of two exploited marine invertebrates in central Chile
(2019) Blanco, Marta; Ospina-Alvarez, Andres; Navarrete, Sergio A.; Fernandez, Miriam
Environmental variability can influence larval development rates and affect critical processes in the dynamics of natural populations, such as dispersal distances and connectivity, when modulated by different larval traits. Knowledge of connectivity patterns in marine populations is fundamental for defining population viability and progressing with management and conservation goals. Here, we developed a biophysical, individual-based larval dispersal model to assess the effect of oceanographic variability and biological traits (i.e. larval diel vertical migration [DVM] and temperature-dependent larval development [PLD]) on recruitment success, dispersal distance, and alongshore connectivity patterns. We selected 2 species exploited by Chilean artisanal fisheries: Loxechinus albus (PLD: 20 d) and Fissurella latimarginata (PLD: 5 d). A sensitivity analysis was used to examine the effect of intrinsic (DVM and PLD) and extrinsic (release depth, latitude, and timing) processes. Release location and timing of release explained respectively 24.30 and 5.54% (F. latimarginata) and 34.8 and 4.19% (L. albus) of the variability observed in recruitment success, and 23.80 and 6.94% (F. latimarginata) and 26.10 and 19.60% (L. albus) of the variability observed in dispersal distance. Most recruitment to local populations was allochthonous, presenting low levels of self-recruitment and local retention, including species with short PLD. Similar geographic patterns of source and destination strengths were observed in both species, showing a geographic mosaic of source and sink populations with relatively higher importance towards the northern region of the study area. Our findings allow us to identify primary determinants of recruitment success and dispersal distance for 2 important exploited species in Chile.
Integration of biophysical connectivity in the spatial optimization of coastal ecosystem services
(ELSEVIER, 2020) Ospina Alvarez, Andres; de Juan, Silvia; Davis, Katrina J.; Gonzalez, Catherine; Fernandez, Miriam; Navarrete, Sergio A.
Ecological connectivity in coastal oceanic waters is mediated by dispersion of the early life stages of marine organisms and conditions the structure of biological communities and the provision of ecosystem services. Integrated management strategies aimed at ensuring long-term service provision to society do not currently consider the importance of dispersal and larval connectivity. A spatial optimization model is introduced to maximise the potential provision of ecosystem services in coastal areas by accounting for the role of dispersal and larval connectivity. The approach combines a validated coastal circulation model that reproduces realistic patterns of larval transport along the coast, which ultimately conditions the biological connectivity and productivity of an area, with additional spatial layers describing potential ecosystem services. The spatial optimization exercise was tested along the coast of Central Chile, a highly productive area dominated by the Humboldt Current. Results show it is unnecessary to relocate existing management areas, as increasing no-take areas by 10% could maximise ecosystem service provision, while improving the spatial representativeness of protected areas and minimizing social conflicts. The location of protected areas was underrepresented in some sections of the study domain. principally due to the restriction of the model to rocky subtidal habitats. Future model developments should encompass the diversity of coastal ecosystems and human activities to inform integrative spatial management. Nevertheless, the spatial optimization model is innovative not only for its integrated ecosystem perspective, but also because it demonstrates that it is possible to incorporate time-varying biophysical connectivity within the optimization problem, thereby linking the dynamics of exploited populations produced by the spatial management regime. (C) 2020 Elsevier B.V. All rights reserved.
Microsatellite evidence for sperm storage and multiple paternity in the marine gastropod Crepidula coquimbensis
(ELSEVIER SCIENCE BV, 2011) Brante, Antonio; Fernandez, Miriam; Viard, Frederique
In gregarious species with copulation and internal fertilization, male-male competition and female cryptic choice may affect reproductive success of both sexes. We carried out a molecular analysis to study paternity and sperm use by females in the protandrous marine brooding gastropod Crepidula coquimbensis. In the field, a single female inhabits an empty hosting shell with up to six males. This gregarious behavior may promote intra-brood multiple paternity if females can store sperm from several consecutive copulations with the surrounding males. To study female sperm usage, the males sharing shelters with five different adult females were collected and preserved for paternity analysis. Females were transported alive to the laboratory and isolated for six months. After that, an additional male was offered to each of the five study females. Once the females had laid capsules, a total of 528 embryos from the five females were assigned paternity based on five microsatellite loci. Paternity analysis showed that every male sharing the empty hosting shell of a female as well as the additional male were assigned fatherhood of embryos laid by this specific female. Females can thus use sperms from multiple males including sperms stored for at least six months. In addition, in four out of the five offspring arrays, a similar contribution of each male to the brood was observed, a pattern associated with the close relationship between the number of fathers observed and the effective paternity index calculated. These results contrast with those of paternity analyses carried out in another species of the same genus. C. fornicata which is characterized by a stacking behavior in which the closest male to the female achieves the highest reproductive success. Male reproductive success may be largely influenced by the aggregation pattern and male mating opportunities in the Crepidula complex, a hypothesis to be examined further by studying other species exhibiting different grouping behavior. (C) 2010 Elsevier B.V. All rights reserved.
Multidimensional data analysis to guide the sustainability of a small-scale fishery affected by poaching
(2022) de Juan, Silvia; Subida, Maria Dulce; Ospina-Alvarez, Andres; Aguilar, Ainara; Fernandez, Miriam
The substantial increase in poaching within the fisheries' management areas (MA) system in central Chile is likely driven by an interplay of socio-economic factors. To assess this problem, the exploitation state of an important benthic resource in the MAs (i.e., keyhole limpet) was related to socio-economic drivers of the fishery. The potential drivers of poaching included the level of formal and informal enforcement and distance to sur-veillance authorities, a rebound effect of fishing effort displacement by MAs, wave exposure and land-based access to the MA, and alternative economic activities in the fishing village. A Bayesian-Belief Network approach was adopted to assess the effects of potential drivers of poaching on the exploitation state of limpets, assessed by the proportion of the catch that is below the minimum legal size and by the relative median size of limpets fished within the MAs in comparison with neighboring open access areas. Results showed the important role of socio-economic (e.g., alternative economic activities in the village) and context variables (e.g., fishing effort displacement or distance to surveillance authorities) as drivers of poaching in the study area. Scenario analysis explored variables that are susceptible to be managed, evidencing that an integrative ecological and socio-economic approach can offer solutions to the unsustainable exploitation of marine resources.
Navigating transformations in governance of Chilean marine coastal resources
(NATL ACAD SCIENCES, 2010) Gelcich, Stefan; Hughes, Terry P.; Olsson, Per; Folke, Carl; Defeo, Omar; Fernandez, Miriam; Foale, Simon; Gunderson, Lance H.; Rodriguez Sickert, Carlos; Scheffer, Marten; Steneck, Robert S.; Castilla, Juan C.
Marine ecosystems are in decline. New transformational changes in governance are urgently required to cope with overfishing, pollution, global changes, and other drivers of degradation. Here we explore social, political, and ecological aspects of a transformation in governance of Chile's coastal marine resources, from 1980 to today. Critical elements in the initial preparatory phase of the transformation were (i) recognition of the depletion of resource stocks, (ii) scientific knowledge on the ecology and resilience of targeted species and their role in ecosystem dynamics, and (iii) demonstration-scale experimental trials, building on smaller-scale scientific experiments, which identified new management pathways. The trials improved cooperation among scientists and fishers, integrating knowledge and establishing trust. Political turbulence and resource stock collapse provided a window of opportunity that triggered the transformation, supported by new enabling legislation. Essential elements to navigate this transformation were the ability to network knowledge from the local level to influence the decision-making processes at the national level, and a preexisting social network of fishers that provided political leverage through a national confederation of artisanal fishing collectives. The resultant governance scheme includes a revolutionary national system of marine tenure that allocates user rights and responsibilities to fisher collectives. Although fine tuning is necessary to build resilience of this new regime, this transformation has improved the sustainability of the interconnected social-ecological system. Our analysis of how this transformation unfolded provides insights into how the Chilean system could be further developed and identifies generalized pathways for improved governance of marine resources around the world.
Phylogeography and Biogeography Concordance in the Marine Gastropod Crepipatella dilatata (Calyptraeidae) along the Southeastern Pacific Coast
(OXFORD UNIV PRESS INC, 2012) Brante, Antonio; Fernandez, Miriam; Viard, Frederique
The biogeography and phylogeography concordance hypothesis suggests that the same factors, for instance physical barriers or environmental gradients, shape both species assemblages and intraspecific genetic structure. In the marine realm, previous studies have however suggested that phylogeographic patterns are also explained by the life-history strategy of the species. However, evidence is contradictory and comes mainly from the northern hemisphere, which is characterized by specific environmental conditions and evolutionary histories of species. In this work, we evaluated the concordance hypothesis in the southern Pacific using the marine gastropod Crepipatella dilatata as a case study. This intertidal species with direct development exhibited a restricted dispersal potential, a feature that contrasts with previous species studied in the same area. Using the gene cytochrome oxidase I, we analyzed 253 individuals sampled at 10 locations covering 543 km of the coast of Chile. The study sites also incorporated 2 biogeographic regions separated by a well-studied biogeographic break (at 30 degrees S). Populations of C dilatata displayed a high degree of genetic structure and a perfect match between phylogeographic and biogeographic breaks at 30 degrees S. When comparing our data with previous research over the same geographic range, life history traits related to dispersal ability seem to be a good proxy for explaining the concordance between biogeography and phylogeography along the southeastern pacific coast. In addition, in this and other marine invertebrate species, gene flow limitations across both sides of the 30 degrees S break may act as a driver of the speciation process.
Territorial User Rights for Fisheries as Ancillary Instruments for Marine Coastal Conservation in Chile
(WILEY-BLACKWELL, 2012) Gelcich, Stefan; Fernandez, Miriam; Godoy, Natalio; Canepa, Antonio; Prado, Luis; Carlos Castilla, Juan
Territorial user rights for fisheries have been advocated as a way to achieve sustainable resource management. However, few researchers have empirically assessed their potential as ancillary marine conservation instruments by comparing them to no-take marine protected areas. In kelp (Lessonia trabeculata) forests of central Chile, we compared species richness, density, and biomass of macroinvertebrates and reef fishes among territorial-user-right areas with low-level and high-level enforcement, no-take marine protected areas, and open-access areas in 42 100-m subtidal transects. We also assessed structural complexity of the kelp forest and substratum composition. Multivariate randomized permutation tests indicated macroinvertebrate and reef fish communities associated with the different access regimes differed significantly. Substratum composition and structural complexity of kelp forest did not differ among access regimes. Univariate analyses showed species richness, biomass, and density of macroinvertebrates and reef fishes were greater in highly enforced territorial-user-right areas and no-take marine protected areas than in open-access areas. Densities of macroinvertebrates and reef fishes of economic importance were not significantly different between highly enforced territorial-user-right and no-take marine protected areas. Densities of economically important macroinvertebrates in areas with low-level enforcement were significantly lower than those in areas with high-level enforcement and no-take marine protected areas but were significantly higher than in areas with open access. Territorial-user-right areas could be important ancillary conservation instruments if they are well enforced.
The effect of temperature on the development of encapsulated embryos of Concholepas concholepas along a latitudinal cline
(2007) Fernandez, Miriam; Calderon, Ricardo; Cancino, Juan M.; Jeno, Katherine
Encapsulating species face more constraints than active brooders in adjusting oxygen supply to the needs of the embryos. Therefore, the packing of embryos in gelatinous egg masses or egg capsules is expected to be adjusted to the temperature and oxygen conditions that the embryos are likely to experience . We studied the patterns of embryo packing (number of embryos per unit area) of the gastropod, Concholepas concholepas, from 14 sites over an extended geographic area spanning 220 of latitude off the coast of Chile. A clear break in the patterns of embryo packing was found at approximately 29 to 300 S. Capsules collected at the sites located north of this break exhibited significantly fewer embryos per unit area than capsules from southern sites. Embryo packing is correlated with mean temperature shortly before egg deposition. A set of laboratory experiments were conducted to determine if the effects of temperature reside in females (incubating females collected in 2 different sites at a common temperature) or in embryos (incubating capsules at different temperatures). Laboratory experiments showed that temperature does not affect the number of embryos that successfully develop in the capsules within the tolerated range of temperatures, but (toes influence developmental success at temperatures that are extreme for the sites of the sample population. Our results suggest that packing and protection of embryos in marine invertebrates might be linked to the capacity to supply oxygen to the brood, which can have important consequences for the distribution of brooding and encapsulating species across temperature gradients.
The effects of temperature and oxygen availability on intracapsular development of Acanthina monodon (Gastropoda: Muricidae)
(2006) Fernandez, Miriam; Pappalardo, Paula; Jeno, Katherine
Freshwater and marine organisms show similar models of parental care and are faced with similar constraints to brood, which suggest that comparable environmental limits drive the evolution of parental care in aquatic systems. In fact, the low diffusion coefficient and solubility of oxygen in aquatic environments affect oxygen acquisition and therefore the capacity to aggregate embryos. The effect of other critical environmental variables, such as temperature, is less clear. We assessed the effects of temperature and oxygen availability on (1) the number of developed and undeveloped encapsulated embryos, (2) the proportion of embryos reaching advanced stages during intracapsular development (counting not only developed and undeveloped embryos but also abnormal embryos), (3) asynchrony in development (estimated only in capsules in which development occurred), and (4) final embryo size, as the first step toward identifying the main factors constraining parental care in the ocean. We used the gastropod Acanthina monodon as a model because it has an extended latitudinal range of distribution and exhibits feeding larvae during intracapsular development. The latter factor is relevant because previous studies have suggested that sibling cannibalism could be triggered by intracapsular competition for oxygen. Freshly laid egg capsules were collected and incubated until embryos hatched under different experimental temperatures (7, 11, 15 and 19 degrees C) and oxygen conditions (hypoxia: 50-60 % air saturation; normoxia; and hyperoxia: 150-160 %). More embryos remained in early stages at the end of the experimental period under hypoxia and at the highest experimental temperature. The mean number of developed embryos was significantly lower under hypoxia conditions than under normoxia and hyperoxia, but was not influenced by temperature. However, temperature negatively affected embryo size of developed embryos and the level of asynchrony (number of different developmental stages per capsule). This suggests that even when a comparable number of embryos develops at high temperature, subsequent survival may be affected, since developed embryos attained smaller sizes. The negative effect of high temperature on embryo aggregation has also been reported for Brachyuran crabs, affecting female patterns of oxygen provision and brooding costs. This evidence suggests that aggregating embryos in the ocean, even under optimum oxygen conditions, may be negatively affected at high temperatures. Spatial patterns of distribution of brooding species in the ocean tend to agree with this prediction. Our analysis is particularly relevant given the current increase in temperature and the proportion of anoxic areas in the world's oceans.
The Hidden Diversity of Temperate Mesophotic Ecosystems from Central Chile (Southeastern Pacific Ocean) Assessed through Towed Underwater Videos
(2023) Campoy, Ana Navarro; Perez-Matus, Alejandro; Wieters, Evie A.; Alarcon-Ireland, Rodrigo; Garmendia, Vladimir; Beldade, Ricardo; Navarrete, Sergio A.; Fernandez, Miriam
The largely unexplored diversity in temperate mesophotic ecosystems (TME, similar to 30-150 m depth) has attracted much attention over the past years. However, the number of studies and knowledge of TME diversity and ecology remains limited and geographically restricted. The absence of information on how assemblages vary across environmental gradients and with depth for most regions also limits our capacity to delimit conservation areas and devise management plans effectively. This study focuses on TME from central Chile and describes the depth distribution of reef fishes and benthic invertebrates and algae for the first time. Through the analysis of towed underwater video surveys between 4.7-95.5 m in multiple sites, we show that total reef fish density and richness decrease with depth but increase with local topographic complexity. The depth-related density varies among fish species and trophic groups, and it reverses in the case of Sebastes oculatus, which increases in density with depth. Sponges and gorgonians dominate benthic assemblages below 20 m depth, and brachiopods and anemones increase below 40 and 60 m, respectively. Some of these species form animal forests which, to some extent, replace the shallow-water kelp forests as structural habitat providers. Nevertheless, the reef fish and benthic community do not show a clear structure with depth or across studied sites. We highlight the urgency to intensify and expand the quantitative characterization of these communities, through this and other methodologies, to better define ecological patterns and advance towards conservation plans for TME, including the Souteastern Pacific region.
The use of fishers' knowledge to assess benthic resource abundance across management regimes in Chilean artisanal fisheries
(2021) Garmendia, Vladimir; Subida, Maria Dulce; Aguilar, Ainara; Fernandez, Miriam
Globally, marine fisheries remain largely unassessed, particularly small-scale fisheries in developing countries. Fishers' knowledge has proven to be valuable to help fill gaps of information in otherwise unassessed fisheries. This study tested the reliability of fishers' knowledge to estimate the abundance of two benthic resources, locos (Concholepas concholepas) and keyhole limpets (Fissurella spp.), across two management regimes, territorial user rights for fisheries (TURF) and open access areas (OAA), over similar to 500 km of coastline in central Chile. Fishers' knowledge (FK) was quantified using systematic interviews and compared to direct assessments (DA). Additionally, resource abundance was compared between the fishing regimes, considering regions with different concentration of TURFs (and consequently different availability of OAAs). The results show that abundances estimated by the two methods were highly consistent for the most valuable resource (the loco) and quite reliable for the keyhole limpet (for 67% of the comparisons). Abundances of both resources were higher in TURFs than in OAAs, a pattern detected by both FK and DA. The results clearly show the potential of this approach to be applied for the Chilean benthic fisheries over large scales. Interestingly, the results also show significantly lower abundance of locos in OAAs than in TURFs at coves immersed in zones with low availability of open access fishing grounds, suggesting the influence of effort displacement after the implementation of TURFs. This ancillary result highlights the need for seascape management plans that consider the potential, unintended effects of TURFs on resources beyond their boundaries. These findings are of both local and global interest, supporting the use of FK to inform management in unassessed small-scale fisheries.
Thermal tolerance of crustacean larvae(zoea I) in two different populations of the kelp crab Taliepus dentatus (Milne-Edwards)
(2009) Storch, Daniela; Santelices, Pedro; Barria, Jessica; Cabeza, Karla; Poertner, Hans-Otto; Fernandez, Miriam
Studies of thermal tolerance in marine ectotherms are key in understanding climate effects on ecosystems; however, tolerance of their larval stages has rarely been analyzed. Larval stages are expected to be particularly sensitive. Thermal stress may affect their potential for dispersal and zoogeographical distribution. A mismatch between oxygen demand and the limited capacity of oxygen supply to tissues has been hypothesized to be the first mechanism restricting survival at thermal extremes. Therefore, thermal tolerance of stage zoea I larvae was examined in two populations of the Chilean kelp crab Taliepus dentatus, which are separated by latitude and the thermal regime. We measured temperature-dependent activity, oxygen consumption, cardiac performance, body mass and the carbon (C) and nitrogen (N) composition in order to: (1) examine thermal effects from organismal to cellular levels, and (2) compare the thermal tolerance of larvae from two environmental temperature regimes. We found that larval performance is affected at thermal extremes indicated by decreases in activity, mainly in maxilliped beat rates, followed by decreases in oxygen consumption rates. Cardiac stroke volume was almost temperature-independent. Through changes in heart rate, cardiac output supported oxygen demand within the thermal window whereas at low and high temperature extremes heart rate declined. The comparison between southern and central populations suggests the adaptation of southern larvae to a colder temperature regime, with higher cardiac outputs due to increased cardiac stroke volumes, larger body sizes but similar body composition as indicated by similar C: N ratios. This limited but clear differentiation of thermal windows between populations allows the species to widen its biogeographical range.
Thermal tolerance of larval stages of the Chilean kelp crab Taliepus dentatus
(INTER-RESEARCH, 2011) Storch, Daniela; Fernandez, Miriam; Navarrete, Sergio A.; Poertner, Hans Otto
Physiological responses of larval stages can differ from those of the adults, affecting key ecological processes. Therefore, developing a mechanistic understanding of larval responses to environmental conditions is essential vis-a-vis climate change. We studied the thermal tolerance windows, defined by lower and upper pejus (Tp) and critical temperatures (Tc), of zoea I, II, and megalopa stages of the Chilean kelp crab Taliepus dentatus. Tp limits determine the temperature range where aerobic scope is maximal and functioning of the organism is unrestrained, and were estimated from direct observations of larval activity. Tc limits define the transition from aerobic to anaerobic metabolism, and were estimated from the relationship between standard metabolic rate and temperature. Zoea I showed the broadest, zoea II an intermediate, and megalopae the narrowest tolerance window (Tp). Optimum performance in megalopae was limited to Tp between 11 and 15 degrees C, while their Tc ranged between 7 and 19 degrees C. Although Tc may be seldom encountered by larvae, the narrower Tp temperatures can frequently expose larvae to unfavorable conditions that can drastically constrain their performance. Temperatures beyond the Tp range of megalopae have been observed in most spring and summer months in central Chile, and can have important consequences for larval swimming performance and impair their ability to avoid predators or settle successfully. Besides the well-documented effects of temperature on development time, variability in field temperatures beyond Tp can affect performance of particular larval stages, which could drive large-scale variability in recruitment and population dynamics of T. dentatus and possibly other invertebrate species.

Browsing by Author "Fernandez, Miriam"

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