Uso da capacidade preditiva como critério bayesiano de adequação de modelos

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Estatística, 2017.Certificar-se de que o modelo probabilístico proposto representa satisfatoriamente o problema e um dos principais passos na modelagem estatística, pois a escolha de um modelo que não esteja bem ajustado pode provocar prejuízos irreparáveis com a tomada de uma decisão errada. Frequentemente, o objetivo da modelagem estatística e a predição de novas observações, fazendo com que avaliar a acurácia do modelo seja imprescindível. Por em, métodos que analisam a capacidade preditiva de um modelo não são muito utilizados por sua complexidade. Este trabalho apresentou uma adaptação para a metodologia de verificação da capacidade preditiva de um modelo proposta por Gelfand (1996), que apesar de simples e intuitiva, não permitia a validação de modelos de uma maneira objetiva. A adaptação possibilitou a definição de um critério de rejeição de modelos, por meio de estudos de simulação, proporcionando um meio de discriminação imparcial para a metodologia. O desenvolvimento da proposta foi realizado sob uma perspectiva bayesiana de inferência, expondo os conceitos utilizados em sua elaboração e apresentando os procedimentos necessários para sua aplicação. A metodologia proposta foi aplicada a base de dados reais para exemplificar sua utilização, possibilitando verificar a praticidade de sua aplicação em situações reais.To ensure that a proposed probability model is a good representation of the problem is one of the main steps of statistical modelling, since choosing a model that does not have a good fit may lead to wrong decisions. Often, the aim of the statistical modelling is the prediction of new observations, making it necessary to ensure the model accuracy. This work provides an adjustment to Gelfand (1996) methodology to validate the model predictive capacity, which, although simple, does not allow an objective form of validation. The adjustment allowed the definition of a model rejection criterion, providing an impartial method to ensure model accuracy. The development of the adjustment was done on a bayesian inference approach, presenting the employed concepts and the necessary procedures to the application. The methodology was tested on a real database, exhibiting the practicality of the method on real applications

Seasonal and interannual variation in high‑latitude estuarine fsh community structure along a glacial to non‑glacial watershed gradient in Southeast Alaska

Along the Gulf of Alaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.This research was funded by the Alaska Established Program to Stimulate Competitive Research (EPSCoR) National Science Foundation award no. OIA-1208927 and award no. OIA-1757348 and by the State of Alaska. In addition, this publication is the result of research sponsored by Alaska Sea Grant with funds from the National Oceanic and Atmospheric Administration Ofce of Sea Grant, Department of Commerce, under grant no. NA14OAR4170079 (projects RR/14-01 & R/32-07 to AHB) and G00009215 (project 14CR-07 to CAB), and from the University of Alaska with funds appropriated by the state. Student support was also provided to DHD through a Ladd Macaulay Graduate Fellowship in Salmon Fisheries Research funded through an endowment and donations provided to the University of Alaska by Douglas Island Pink and Chum, Inc. (DIPAC), and to NCL by the North Pacifc Research Board through a Graduate Student Research Award. We are grateful to Franz Mueter for assistance with the analysis and to the many students and volunteers who participated in feldwork. Thanks to two anonymous reviewers whose comments improved the paper. This research was approved by the University of Alaska Institutional Animal Care and Use Committee (protocols 465729, 880562, 479533, 1238650).Ye

Seasonal and interannual variation in high‑latitude estuarine fsh community structure along a glacial to non‑glacial watershed gradient in Southeast Alaska

Along the Gulf of Alaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.This research was funded by the Alaska Established Program to Stimulate Competitive Research (EPSCoR) National Science Foundation award no. OIA-1208927 and award no. OIA-1757348 and by the State of Alaska. In addition, this publication is the result of research sponsored by Alaska Sea Grant with funds from the National Oceanic and Atmospheric Administration Ofce of Sea Grant, Department of Commerce, under grant no. NA14OAR4170079 (projects RR/14-01 & R/32-07 to AHB) and G00009215 (project 14CR-07 to CAB), and from the University of Alaska with funds appropriated by the state. Student support was also provided to DHD through a Ladd Macaulay Graduate Fellowship in Salmon Fisheries Research funded through an endowment and donations provided to the University of Alaska by Douglas Island Pink and Chum, Inc. (DIPAC), and to NCL by the North Pacifc Research Board through a Graduate Student Research Award. We are grateful to Franz Mueter for assistance with the analysis and to the many students and volunteers who participated in feldwork. Thanks to two anonymous reviewers whose comments improved the paper. This research was approved by the University of Alaska Institutional Animal Care and Use Committee (protocols 465729, 880562, 479533, 1238650).Ye

Assessing prevalence and correlates of blue‑colored fesh in lingcod (Ophiodon elongatus) across their geographic range

Intraspecific variation in external and internal pigmentation is common among fishes and explained by a variety of biological and ecological factors. Blue-colored flesh in fishes is relatively rare but has been documented in some species of the sculpin, greenling, and perch families. Diet, starvation, photoprotection, and camouflage have all been suggested as proximate mechanisms driving blue flesh, but causal factors are poorly understood. We evaluated the relative importance of biological and spatial factors that could explain variation in blue coloration in 2021 lingcod (Ophiodon elongatus) captured across their range in the northeastern Pacific, from southeast Alaska to southern California. The probability of having blue flesh was highest for fish that were female, caught in shallower water, and smaller in body size. The incidence of blueness varied by region (4–25% of all fish) but was also confounded by differences in sex ratios of fish caught among regions. We analyzed the multivariate fatty acid composition of a subset of 175 fish from across the sampling range to test for differences in trophic biomarkers in blue lingcod. Lingcod fatty acid composition differed between regions and flesh colors but not between sexes. Blue-fleshed fish had lower concentrations of total fatty acids, 18:1ω-9, 16:1ω-7, 18:1ω-7, and ω-6 fatty acids, suggesting differences in energetics and energy storage in blue fish. While our data indicate potential links between diet and blue flesh in lingcod, important questions remain about the physiological mechanisms governing blueness and its biological consequences.Ye

Spatial and temporal patterns of vertical distribution for three planktivorous fishes in Lake Washington

We sampled three limnetic fish species: juvenile sockeye salmon (Oncorhynchus nerka), three-spine stickleback (Gasterosteus aculeatus) and longfin smelt (Spirinchus thaleichthys) in Lake Washington to quantify species-specific patterns of diel vertical migration (DVM). Catch-per-unit-effort data analysed from 15 years of midwater trawling documented seasonal and diel differences in vertical distributions for each species. These results were consistent with the hypothesis that the patterns of DVM in Lake Washington were affected by life history, size and morphology. Sockeye salmon showed clear DVM in spring but essentially no DVM in fall, remaining in deep water, whereas three-spine sticklebacks were prevalent at the surface at night in both seasons. In fall, distribution patterns may be explained by differences in thermal performance (e.g., sticklebacks favouring warm water), but the patterns were also consistent with inter-specific differences in predation risk. Younger sockeye salmon and longfin smelt were present in greater proportions higher in the water column during dusk and night periods than older conspecifics. Compared with sockeye salmon, the greater use by three-spine sticklebacks of surface waters throughout the diel cycle during weak thermal stratification in spring was consistent with the hypothesis that sticklebacks’ armour reduces predation risk, but use of this warmer, metabolically beneficial stratum may also have promoted growth. This study illustrates variation in the vertical distribution of three sympatric planktivores and offers broader implications for the DVM phenomenon and applied lake ecology

Historical Patterns and Drivers of Spatial Changes in Recreational Fishing Activity in Puget Sound, Washington

<div><p>Small-scale fisheries are the primary users of many coastal fish stocks; yet, spatial and temporal patterns of recreational and subsistence fishing in coastal marine ecosystems are poorly documented. Knowledge about the spatial distribution of fishing activities can inform place-based management that balances species conservation with opportunities for recreation and subsistence. We used a participatory mapping approach to document changes in spatial fishing patterns of 80 boat-based recreational anglers from 1950 to 2010 in Puget Sound, Washington, USA. Hand-drawn fishing areas for salmon, rockfishes, flatfishes, and crabs were digitized and analyzed in a Geographic Information System. We found that recreational fishing has spanned the majority of Puget Sound since the 1950s, with the heaviest use limited to small areas of central and northern Puget Sound. People are still fishing in the same places they were decades ago, with relatively little change in specific locations despite widespread declines in salmon and bottomfish populations during the second half of the 20^th century. While the location of core fishing areas remained consistent, the size of those areas and intensity of use changed over time. The size of fishing areas increased through the 2000s for salmon but declined after the 1970s and 1980s for rockfishes, flatfishes, and crabs. Our results suggest that the spatial extent of recreational bottomfishing increased after the 1960s, when the availability of motorized vessels and advanced fish-finding technologies allowed anglers to expand their scope beyond localized angling from piers and boathouses. Respondents offered a wide range of reasons for shifts in fishing areas over time, reflecting substantial individual variation in motivations and behaviors. Changes in fishing areas were most commonly attributed to changes in residence and declines in target species and least tied to fishery regulations, despite the implementation of at least 25 marine preserves since 1970.</p></div

Spatial distribution of recreational fishing for salmon, rockfishes, flatfishes, and crabs in the San Juan Islands.

<p>Maps for individual decades are shown, from the 1960s to the 2000s. The intensity of space use by fishers is represented as the percentage of respondents who fished in each 0.8 x 0.8 km grid cell. The lower right panel shows the change in percentage of respondents from the 1960s to the 2000s. Positive values indicate that the percentage of respondents fishing in an area was higher in the 2000s than the 1960s.</p

Respondents’ reasons for changes in the geographic location and/or size of fishing areas.

<p>Respondents’ reasons for changes in the geographic location and/or size of fishing areas.</p

Spatial distribution of recreational fishing for salmon, rockfishes, flatfishes, and crabs in central Puget Sound.

<p>Maps for individual decades are shown, from the 1960s to the 2000s. The intensity of space use by fishers is represented as the percentage of respondents who fished in each 0.8 x 0.8 km grid cell. The lower right panel shows the change in percentage of respondents from the 1960s to the 2000s. Positive values indicate that the percentage of respondents fishing in an area was higher in the 2000s than the 1960s.</p