Departamento de Ciencias Agropecuarias y Acuícolas

Organización superior

Facultad de Ciencias

Buscar

Publicaciones

Mostrando 1 - 10 de 35

Some of the metrics are blocked by your
consent settings
DOI 10.1016/j.heliyon.2023.e16336
Economic and financial risks of commercial tilapia cage culture in a neotropical reservoir
2023-06
Brande, Maicon da Rocha
;
Santos, David Ferreira Lopes
;
Fialho, Naor Silveira
;
Proenca, Danilo Cintra
;
Gallardo Ojeda, Pablo Rodrigo
;
Godoi, Flavia C. M.
;
Roubach, Rodrigo
;
Bueno, Guilherme Wolff
The aim of this study was to analyze the financial and economic risks of tilapia cage culture across different production water volumes (m3). The production water volumes evaluated were 10 to 50 thousand m3 (Small Volume, SV), 51 to 150 thousand m3 (Medium Volume, MV), 151 to 300 thousand m3 (Large Volume, LV), and >301 thousand m3 (Extra-Large Volume, ELV). Produc-tivity and economic data were obtained from a commercial Nile tilapia cage farm with 232 net cages installed in a neotropical reservoir, in Brazil, from 2017 to 2019. Cost and profitability analyses, economic feasibility, and risk and sensitivity analyses were performed using a Monte Carlo simulation. The implementation of commercial tilapia cage farming relies mainly on feed prices. The initial investment demand is proportional to the size of the farms. On the other hand, MV, LV, and ELV tilapia farms showed the lowest financial risks despite the higher investments. These farms presented a medium-low risk at&AP;39% probability, whereas the SV farm presented a medium to medium-high risk at 51.17% probability. Thus, fish farms with a production volume above 51 thousand m3 tend to be more profitable and have a&AP;36% probability of low financial and economic risk with a Payback period of fewer than 10 years, mainly due to the lower feed costs per mass of fish produced. This study assists investors in choosing a better path toward a more viable and profitable activity.
Some of the metrics are blocked by your
consent settings
DOI 10.1016/j.heliyon.2023.e16336
Economic and financial risks of commercial tilapia cage culture in a neotropical reservoir
2023-06
Brande, Maicon da Rocha
;
Santos, David Ferreira Lopes
;
Fialho, Naor Silveira
;
Proenca, Danilo Cintra
;
Gallardo Ojeda, Pablo Rodrigo
;
Godoi, Flavia C. M.
;
Roubach, Rodrigo
;
Bueno, Guilherme Wolff
The aim of this study was to analyze the financial and economic risks of tilapia cage culture across different production water volumes (m3). The production water volumes evaluated were 10 to 50 thousand m3 (Small Volume, SV), 51 to 150 thousand m3 (Medium Volume, MV), 151 to 300 thousand m3 (Large Volume, LV), and >301 thousand m3 (Extra-Large Volume, ELV). Produc-tivity and economic data were obtained from a commercial Nile tilapia cage farm with 232 net cages installed in a neotropical reservoir, in Brazil, from 2017 to 2019. Cost and profitability analyses, economic feasibility, and risk and sensitivity analyses were performed using a Monte Carlo simulation. The implementation of commercial tilapia cage farming relies mainly on feed prices. The initial investment demand is proportional to the size of the farms. On the other hand, MV, LV, and ELV tilapia farms showed the lowest financial risks despite the higher investments. These farms presented a medium-low risk at&AP;39% probability, whereas the SV farm presented a medium to medium-high risk at 51.17% probability. Thus, fish farms with a production volume above 51 thousand m3 tend to be more profitable and have a&AP;36% probability of low financial and economic risk with a Payback period of fewer than 10 years, mainly due to the lower feed costs per mass of fish produced. This study assists investors in choosing a better path toward a more viable and profitable activity.
Scopus© Citations 7 2
Some of the metrics are blocked by your
consent settings
DOI 10.1002/hyp.14698
On the urgent need for standardization in isotope-based ecohydrological investigations
2022-10
Millar, Cody
;
Janzen, Kim
;
Nehemy, Magali F.
;
Koehler, Geoff
;
Hervé Fernandez, Pedro Alejandro
;
Wang, Hongxiu
;
Orlowski, Natalie
;
Barbeta, Adria
;
McDonnell, Jeffrey J.
Ecohydrological investigations commonly use the stable isotopes of water (hydrogen and oxygen) as conservative ecosystem tracers. This approach requires accessing and analysing water from plant and soil matrices. Generally, there are six steps involved to retrieve hydrogen and oxygen isotope values from these matrices: (1) sampling, (2) sample storage and transport, (3) extraction, (4) pre-analysis processing, (5) isotopic analysis, and (6) post-processing and correction. At each step, cumulative errors can be introduced which sum to non-trivial magnitudes. These can impact subsequent interpretations about water cycling and partitioning through the soil-plant-atmosphere continuum. At each of these steps, there are multiple possible options to select from resulting in tens of thousands of possible combinations used by researchers to go from plant and soil samples to isotopic data. In a newly emerging field, so many options can create interpretive confusion and major issues with data comparability. This points to the need for development of shared standardized approaches. Here we critically examine the state of the process chain, reflecting on the issues associated with each step, and provide suggestions to move our community towards standardization. Assessing this shared 'process chain' will help us see the problem in its entirety and facilitate community action towards agreed upon standardized approaches.
Some of the metrics are blocked by your
consent settings
DOI 10.1002/hyp.14698
On the urgent need for standardization in isotope-based ecohydrological investigations
2022-10
Millar, Cody
;
Janzen, Kim
;
Nehemy, Magali F.
;
Koehler, Geoff
;
Hervé Fernandez, Pedro Alejandro
;
Wang, Hongxiu
;
Orlowski, Natalie
;
Barbeta, Adria
;
McDonnell, Jeffrey J.
Ecohydrological investigations commonly use the stable isotopes of water (hydrogen and oxygen) as conservative ecosystem tracers. This approach requires accessing and analysing water from plant and soil matrices. Generally, there are six steps involved to retrieve hydrogen and oxygen isotope values from these matrices: (1) sampling, (2) sample storage and transport, (3) extraction, (4) pre-analysis processing, (5) isotopic analysis, and (6) post-processing and correction. At each step, cumulative errors can be introduced which sum to non-trivial magnitudes. These can impact subsequent interpretations about water cycling and partitioning through the soil-plant-atmosphere continuum. At each of these steps, there are multiple possible options to select from resulting in tens of thousands of possible combinations used by researchers to go from plant and soil samples to isotopic data. In a newly emerging field, so many options can create interpretive confusion and major issues with data comparability. This points to the need for development of shared standardized approaches. Here we critically examine the state of the process chain, reflecting on the issues associated with each step, and provide suggestions to move our community towards standardization. Assessing this shared 'process chain' will help us see the problem in its entirety and facilitate community action towards agreed upon standardized approaches.
Scopus© Citations 42
Some of the metrics are blocked by your
consent settings
DOI 10.1016/j.actao.2022.103853
Patterns of guanaco distribution and microhabitat use in Tierra del Fuego: From protected to sheep ranching areas
2022-10
Iranzo, Esperanza C.
;
Smith, Carollyne
;
Moraga, Claudio A.
;
Radic Schilling, Sergio Javier
;
Corti, Paulo
Wild herbivore distribution responds to habitat and forage availability modulated by predation risk and inter-specific interactions. Nowadays, the study of distribution and abundance of wild and domestic herbivores have regained importance to understand and diminish conservation conflicts in productive lands worldwide. Contiguous ranching and protected areas have created conflicting scenarios when wild ungulate populations increase and redistribute in livestock rangelands, because of competition for food and disease transmission. Consequently, understanding wild ungulate distribution and density patterns is critical to inform efficient management strategies for livestock grazing and wild ungulate coexistence. Here we analyze guanaco (Lama guanicoe) density and distribution, and compare habitat and microhabitat use (plant biomass, species richness, and diversity) in a protected area and in surrounding sheep ranches of Tierra del Fuego. Density of guanaco was similar between protected area and ranches, but proportion of groups and average group size were larger on ranches, and total guanaco density was also higher outside than within the protected area, which contrasts with previous studies. Use of microhabitat features was also different between both management regimes. Guanaco used areas with higher vegetation biomass, plant composition and richness in the protected area than on ranches. These results suggest that both intrinsic (socio-biological) and extrinsic (forage availability and human distur-bance) factors influence density and distribution patterns as well as microhabitat use by the guanaco, which have large implications for its conservation.
Scopus© Citations 5 1
Some of the metrics are blocked by your
consent settings
DOI 10.3389/fcosc.2021.647798
Genetic Approach on Sanionia uncinata (Hedw.) Loeske to Evaluate Representativeness of in situ Conservation Areas Among Protected and Neighboring Free Access Areas in Maritime Antarctica and Southern Patagonia
2021-11-19
Hebel Carreño, Ingrid Adela
;
Gonzalez, Inti
;
Jana, Ricardo
The Antarctic Specially Protected Areas (ASPAs) are zones with restricted access to protect outstanding environmental, scientific, historic, aesthetic, or wilderness values adopted inside the Antarctic Treaty System. Meanwhile, in southern Patagonia, conservation initiatives are implemented by the state of Chile and private entities. However, both are considered unrepresentative. Our work evaluates the representativeness of the in situ conservation through a genetic approach of the moss Sanionia uncinata (Hedw.) Loeske among protected and neighboring free access areas in Maritime Antarctica and southern Patagonia. We discuss observed presence with both current and reconstructed past potential niche distributions (11 and 6 ka BP) in the Fildes Peninsula on King George Island. Results showed occurrence of several spatially genetic subpopulations distributed inside and among ASPA and free access sites. Some free access sites showed a higher amount of polymorphism compared with ASPA, having ancestry in populations developed in those places since 6 ka BP. The different spatial and temporal hierarchies in the analysis suggest that places for conservation of this species in Maritime Antarctica are not well-represented, and that some free access areas should be considered. This work represents a powerful multidisciplinary approach and a great challenge for decision-makers to improve the management plans and the sustainable development in Antarctica.
Scopus© Citations 2 1
Some of the metrics are blocked by your
consent settings
DOI 10.3390/ani11113333
Behavioural Indicators of Intra- and Inter-Specific Competition: Sheep Co-Grazing with Guanaco in the Patagonian Steppe
2021-11
Fernandez, Tomas
;
Lancaster, Alex
;
Moraga, Claudio A.
;
Radic Schilling, Sergio Javier
;
von Hardenberg, Achaz
;
Corti, Paulo
In extensive livestock ranching, where animals are maintained at high numbers, competition between individuals is expected, but not generally assumed. To compensate for reduced food availability, herbivores modify their feeding behaviour, which can be used as an indicator of competition. We investigated behavioural changes of domestic sheep in Chilean Patagonia in response to herd size, food availability, and the presence of a wild competitor, the guanaco, considered a problem for sheep production by ranchers. Large sheep herds were associated with a decrease in sheep grazing, while food availability increased time spent feeding. Guanaco had no effect on sheep behaviours. Behavioural changes were mostly associated with competition between individual sheep and not with guanaco. We suggest that to improve sheep production, ranchers should focus on sheep management at appropriate herd sizes according to grassland capacities. In extensive livestock production, high densities may inhibit regulation processes, maintaining high levels of intraspecific competition over time. During competition, individuals typically modify their behaviours, particularly feeding and bite rates, which can therefore be used as indicators of competition. Over eight consecutive seasons, we investigated if variation in herd density, food availability, and the presence of a potential competitor, the guanaco (Lama guanicoe), was related with behavioural changes in domestic sheep in Chilean Patagonia. Focal sampling, instantaneous scan sampling, measures of bite and movement rates were used to quantify behavioural changes in domestic sheep. We found that food availability increased time spent feeding, while herd density was associated with an increase in vigilant behaviour and a decrease in bite rate, but only when food availability was low. Guanaco presence appeared to have no impact on sheep behaviour. Our results suggest that the observed behavioural changes in domestic sheep are more likely due to intraspecific competition rather than interspecific competition. Consideration of intraspecific competition where guanaco and sheep co-graze on pastures could allow management strategies to focus on herd density, according to rangeland carrying capacity.
Scopus© Citations 6 3
Some of the metrics are blocked by your
consent settings
DOI 10.1002/rcm.9118
Organic contamination detection for isotopic analysis of water by laser spectroscopy
2021-08-15
Millar, Cody
;
Janzen, Kim
;
Nehemy, Magali F.
;
Koehler, Geoff
;
Hervé Fernandez, Pedro Alejandro
;
McDonnell, Jeffrey J.
Rationale Hydrogen and oxygen stable isotope ratios (delta H-2, delta O-17, and delta O-18 values) are commonly used tracers of water. These ratios can be measured by isotope ratio infrared spectroscopy (IRIS). However, IRIS approaches are prone to errors induced by organic compounds present in plant, soil, and natural water samples. A novel approach using O-17-excess values has shown promise for flagging spectrally contaminated plant samples during IRIS analysis. A systematic assessment of this flagging system is needed to prove it useful. Methods Errors induced by methanol and ethanol water mixtures on measured IRIS and isotope ratio mass spectrometry (IRMS) results were evaluated. For IRIS analyses both liquid- and vapour-mode (via direct vapour equilibration) methods are used. The delta H-2, delta O-17, and delta O-18 values were measured and compared with known reference values to determine the errors induced by methanol and ethanol contamination. In addition, the O-17-excess contamination detection approach was tested. This is a post-processing detection tool for both liquid and vapour IRIS triple-isotope analyses, utilizing calculated O-17-excess values to flag contaminated samples. Results Organic contamination induced significant errors in IRIS results, not seen in IRMS results. Methanol caused larger errors than ethanol. Results from vapour-IRIS analyses had larger errors than those from liquid-IRIS analyses. The O-17-excess approach identified methanol driven error in liquid- and vapour-mode IRIS samples at levels where isotope results became unacceptably erroneous. For ethanol contaminated samples, a mix of erroneous and correct flagging occurred with the O-17-excess method. Our results indicate that methanol is the more problematic contaminant for data corruption. The O-17-excess method was therefore useful for data quality control. Conclusions Organic contamination caused significant errors in IRIS stable isotope results. These errors were larger during vapour analyses than during liquid IRIS analyses, and larger for methanol than ethanol contamination. The O-17-excess method is highly sensitive for detecting narrowband (methanol) contamination error in vapour and liquid analysis modes in IRIS.
1
Some of the metrics are blocked by your
consent settings
DOI 10.1002/rcm.9118
Organic contamination detection for isotopic analysis of water by laser spectroscopy
2021-08-15
Millar, Cody
;
Janzen, Kim
;
Nehemy, Magali F.
;
Koehler, Geoff
;
Hervé Fernandez, Pedro Alejandro
;
McDonnell, Jeffrey J.
Rationale Hydrogen and oxygen stable isotope ratios (delta H-2, delta O-17, and delta O-18 values) are commonly used tracers of water. These ratios can be measured by isotope ratio infrared spectroscopy (IRIS). However, IRIS approaches are prone to errors induced by organic compounds present in plant, soil, and natural water samples. A novel approach using O-17-excess values has shown promise for flagging spectrally contaminated plant samples during IRIS analysis. A systematic assessment of this flagging system is needed to prove it useful. Methods Errors induced by methanol and ethanol water mixtures on measured IRIS and isotope ratio mass spectrometry (IRMS) results were evaluated. For IRIS analyses both liquid- and vapour-mode (via direct vapour equilibration) methods are used. The delta H-2, delta O-17, and delta O-18 values were measured and compared with known reference values to determine the errors induced by methanol and ethanol contamination. In addition, the O-17-excess contamination detection approach was tested. This is a post-processing detection tool for both liquid and vapour IRIS triple-isotope analyses, utilizing calculated O-17-excess values to flag contaminated samples. Results Organic contamination induced significant errors in IRIS results, not seen in IRMS results. Methanol caused larger errors than ethanol. Results from vapour-IRIS analyses had larger errors than those from liquid-IRIS analyses. The O-17-excess approach identified methanol driven error in liquid- and vapour-mode IRIS samples at levels where isotope results became unacceptably erroneous. For ethanol contaminated samples, a mix of erroneous and correct flagging occurred with the O-17-excess method. Our results indicate that methanol is the more problematic contaminant for data corruption. The O-17-excess method was therefore useful for data quality control. Conclusions Organic contamination caused significant errors in IRIS stable isotope results. These errors were larger during vapour analyses than during liquid IRIS analyses, and larger for methanol than ethanol contamination. The O-17-excess method is highly sensitive for detecting narrowband (methanol) contamination error in vapour and liquid analysis modes in IRIS.
Scopus© Citations 21 2
Some of the metrics are blocked by your
consent settings
DOI 10.4067/s0717-66432021000100038
Ecological characterization of an ombrogenic peatland in magallanes: Towards a proposal of bioindicators for environmental monitoring Caracterización ecológica de una turbera ombrogénica en magallanes: Hacia una propuesta de bioindicadores de monitoreo ambiental
2021-06-01
Monsalve, Erika
;
Muñoz Arriagada, Rene Santiago
;
Bahamonde, Nelson
;
Vidal Ojeda, Osvaldo Javier
Ombrogenic peat bogs are ecologically extreme ecosystems, where the restrictive conditions such as anoxia, high acidity and low availability of nutrients allow a gradual accumulation of the organic substrate known as peat. This substrate is of great commercial interest because it is exploited for horticultural purposes and energy biomass. The exploitation of peat, however, involves the removal of vegetation, which has an important effect on secondary succession and ecosystem resilience. The flora and vegetation of peat bogs in the Brunswick Peninsula (Magallanes), in an area susceptible to mining exploitation, was studied to characterize ecological indicators. Phytosociological surveys were carried out to determine attributes of composition and structure at the community and landscape scale. This information was collated with satellite images and analyzed by univariate procedures (e.g. KW, Pearson) and multivariate (e.g. NMDS, ISA, ANOSIM). The following types of ombrogenic peat bogs were differentiated: graminoid, chamaephytic, Sphagnum and pulvinated peat bogs, which were associated with a terrestrialization to paludification gradient, and decomposition. The highest average richness was recorded in the pulvinated peat bogs. The chamaephytic and graminoid bogs has the largest areas, while the pulvinated were distributed in a few hectares. Diagnostic species (e.g. Caltha appendiculata, Donatia fascicularis, Drosera uniflora, Myrteola nummularia) were associated with one or another type of vegetation, showing ecological preferences. No exotic species were recorded. This information can help define critical levels of resilience and propose management and restoration strategies in post-disturbance abandoned peatlands.

Departamento de Ciencias Agropecuarias y Acuícolas

Buscar

Ajustes

Filtrar por:

Ajustes

Publicaciones