The Experts below are selected from a list of 426 Experts worldwide ranked by ideXlab platform
Aimee A. Keller - One of the best experts on this subject based on the ideXlab platform.
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Impact of light on catch rate of four demersal fish species during the 2009–2010 U.S. west coast groundfish bottom trawl survey
Fisheries Research, 2015Co-Authors: Mark J. Bradburn, Aimee A. KellerAbstract:Abstract To determine the influence of light on catch of demersal fish, we examined the relationship between near-bottom light levels, catch rates, and catch probability for four abundant groundfish species well represented in annual bottom trawl surveys on the U.S. west coast: Arrowtooth Flounder ( Atheresthes stomias ), greenstriped rockfish ( Sebastes elongatus ), longnose skate ( Raja rhina ), and Pacific hake ( Merluccius productus ). Relative downward irradiance was measured with MK-9 archival tags during annual trawl surveys along the U.S. west coast in 2009 and 2010. Near-bottom light levels were recorded for 818 hauls at depths less than 400 m. Significant linear relationships were observed between catch per unit effort (CPUE, kg ha −1 ) and near-bottom light ( P 10 light (μE m −2 s −1 ). CPUE of greenstriped rockfish increased 39% per unit increase in log 10 light. Light, depth, and latitude explained 15–47% of the variance in CPUE for the four species. Catch probability was significantly related to light, depth, latitude, and relative time of day ( P
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Shifts in condition and distribution of eastern North Pacific flatfish along the U.S. west coast (2003–2010)
Deep Sea Research Part I: Oceanographic Research Papers, 2013Co-Authors: Aimee A. Keller, Mark J. Bradburn, Victor H. SimonAbstract:Abstract Flatfish condition indices and distribution were examined along the U.S. west coast (55–1280 m) in relation to environmental variability and biomass using data from ten frequently occurring species collected in annual groundfish surveys from 2003 to 2010. The study was conducted during a period characterized by a cooling trend in the northern California Current system and by declining biomass for flatfish in general. Annual condition indices for six species (Arrowtooth Flounder, Dover sole, English sole, Pacific sanddab, petrale sole, and rex sole) were significantly related either to large-scale climatic indices (Pacific Decadal Oscillation, Multivariate El Nino–Southern Oscillation Index, North Pacific Gyre Oscillation) and/or annual biomass levels. Condition was most closely related to environmental effects rather than either biomass alone or both variables, with condition typically higher during cool climatic conditions. A similar analysis revealed that changes in distribution (measured as variation in annual catch-weighted mean latitude, longitude, depth and temperature) tended to be best described by models incorporating environmental effects and biomass rather than either variable alone. Linear trends in the center of distribution along a southeast–northwest axis were significant for seven species (Arrowtooth Flounder, deepsea sole, Dover sole, flathead sole, Pacific sanddab, petrale sole, and slender sole) with a tendency for flatfish to be displaced towards the southeast as environmental conditions shifted from warm to cooler conditions and biomass declined. A spatial distribution analysis indicated that for the majority of species (80%) the greatest magnitude of displacement (km) occurred when the centers of biomass were compared between environmental phases (average annual displacement 34 km) rather than changing biomass levels (average displacement 24 km). Taken together both approaches revealed that environmental changes and variation in biomass play significant roles in flatfish distribution.
Lorenzo Ciannelli - One of the best experts on this subject based on the ideXlab platform.
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assessing the potential for competition between pacific halibut hippoglossus stenolepis and Arrowtooth Flounder atheresthes stomias in the gulf of alaska
PLOS ONE, 2018Co-Authors: Cheryl L Barnes, Anne H Beaudreau, Mary E Hunsicker, Lorenzo CiannelliAbstract:Pacific Halibut (Hippoglossus stenolepis) support culturally and economically important fisheries in the Gulf of Alaska, though recent decreases in mean size-at-age have substantially reduced fishery yields, generating concerns among stakeholders and resource managers. Among the prevailing hypotheses for reduced size-at-age is intensified competition with Arrowtooth Flounder (Atheresthes stomias), a groundfish predator that exhibited nearly five-fold increases in biomass between the 1960s and mid-2010s. To assess the potential for competition between Pacific Halibut and Arrowtooth Flounder, we evaluated their degree of spatiotemporal and dietary overlap in the Gulf of Alaska using bottom trawl survey and food habits data provided by the Alaska Fisheries Science Center (NOAA; 1990 to 2017). We restricted analyses to fish measuring 30 to 69 cm fork length and used a delta modeling approach to quantify species-specific presence-absence and catch-per-unit-effort as a function of survey year, tow location, depth, and bottom temperature. We then calculated an index of spatial overlap across a uniform grid by multiplying standardized predictions of species’ abundance. Dietary overlap was calculated across the same uniform grid using Schoener’s similarity index. Finally, we assessed the relationship between spatial and dietary overlap as a measure of resource partitioning. We found increases in spatial overlap, moving from east to west in the Gulf of Alaska (eastern: 0.13 ± 0.20; central: 0.21 ± 0.11; western: 0.31 ± 0.13 SD). Dietary overlap was low throughout the study area (0.13 ± 0.20 SD). There was no correlation between spatial and dietary overlap, suggesting an absence of resource partitioning along the niche dimensions examined. This finding provides little indication that competition with Arrowtooth Flounder was responsible for changes in Pacific Halibut alHHsize-at-age in the Gulf of Alaska; however, it does not rule out competitive interactions that may have affected resource use prior to standardized data collection or at different spatiotemporal scales.
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Analytical framework used to quantify spatial overlap between Pacific Halibut and Arrowtooth Flounder.
2018Co-Authors: Cheryl L Barnes, Anne H Beaudreau, Mary E Hunsicker, Lorenzo CiannelliAbstract:First, bottom trawl survey data from the Gulf of Alaska and generalized additive models were used to separately quantify presence-absence and catch-per-unit-effort (CPUE; number per ha) as a function of survey year, tow location (latitude, longitude), depth, and bottom temperature. Model results were used to estimate the probability of occurrence and predicted abundance for Pacific Halibut or Arrowtooth Flounder in each combination of survey year i and uniform grid cell j. These predictions were multiplied to estimate abundance, which was then standardized by dividing each survey year-grid cell value by that species’ maximum across all years. Finally, standardized abundances for Pacific Halibut and Arrowtooth Flounder were multiplied to approximate spatial overlap in each survey year and grid cell. Analytical methods were modified from those described by Hunsicker et al. [32] and Shelton et al. [33].
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Number of tows that captured at least one Arrowtooth Flounder (n = 7,422) measuring 30 to 69 cm fork length.
2018Co-Authors: Cheryl L Barnes, Anne H Beaudreau, Mary E Hunsicker, Lorenzo CiannelliAbstract:Number of tows that captured at least one Arrowtooth Flounder (n = 7,422) measuring 30 to 69 cm fork length.
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Assessing the potential for competition between Pacific Halibut (Hippoglossus stenolepis) and Arrowtooth Flounder (Atheresthes stomias) in the Gulf of Alaska - Fig 3
2018Co-Authors: Cheryl L Barnes, Anne H Beaudreau, Mary E Hunsicker, Lorenzo CiannelliAbstract:Mean standardized abundances for (A) Pacific Halibut and (B) Arrowtooth Flounder (1990 to 2017). Filled squares represent individual 100 km x 100 km grid cell estimates. Polygons denote International North Pacific Fisheries Commission (INPFC) statistical areas (black outlines) and International Pacific Halibut Commission (IPHC) regulatory areas (blue-shaded outlines) in the Gulf of Alaska.
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Climate and Demography Dictate the Strength of Predator-Prey Overlap in a Subarctic Marine Ecosystem
PloS one, 2013Co-Authors: Mary E Hunsicker, Lorenzo Ciannelli, Kevin M. Bailey, Stephani G. Zador, Leif Christian StigeAbstract:There is growing evidence that climate and anthropogenic influences on marine ecosystems are largely manifested by changes in species spatial dynamics. However, less is known about how shifts in species distributions might alter predator-prey overlap and the dynamics of prey populations. We developed a general approach to quantify species spatial overlap and identify the biotic and abiotic variables that dictate the strength of overlap. We used this method to test the hypothesis that population abundance and temperature have a synergistic effect on the spatial overlap of Arrowtooth Flounder (predator) and juvenile Alaska walleye pollock (prey, age-1) in the eastern Bering Sea. Our analyses indicate that (1) Flounder abundance and temperature are key variables dictating the strength of Flounder and pollock overlap, (2) changes in the magnitude of overlap may be largely driven by density-dependent habitat selection of Flounder, and (3) species overlap is negatively correlated to juvenile pollock recruitment when Flounder biomass is high. Overall, our findings suggest that continued increases in Flounder abundance coupled with the predicted long-term warming of ocean temperatures could have important implications for the predator-prey dynamics of Arrowtooth Flounder and juvenile pollock. The approach used in this study is valuable for identifying potential consequences of climate variability and exploitation on species spatial dynamics and interactions in many marine ecosystems.
Kevin M. Bailey - One of the best experts on this subject based on the ideXlab platform.
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Climate and Demography Dictate the Strength of Predator-Prey Overlap in a Subarctic Marine Ecosystem
PloS one, 2013Co-Authors: Mary E Hunsicker, Lorenzo Ciannelli, Kevin M. Bailey, Stephani G. Zador, Leif Christian StigeAbstract:There is growing evidence that climate and anthropogenic influences on marine ecosystems are largely manifested by changes in species spatial dynamics. However, less is known about how shifts in species distributions might alter predator-prey overlap and the dynamics of prey populations. We developed a general approach to quantify species spatial overlap and identify the biotic and abiotic variables that dictate the strength of overlap. We used this method to test the hypothesis that population abundance and temperature have a synergistic effect on the spatial overlap of Arrowtooth Flounder (predator) and juvenile Alaska walleye pollock (prey, age-1) in the eastern Bering Sea. Our analyses indicate that (1) Flounder abundance and temperature are key variables dictating the strength of Flounder and pollock overlap, (2) changes in the magnitude of overlap may be largely driven by density-dependent habitat selection of Flounder, and (3) species overlap is negatively correlated to juvenile pollock recruitment when Flounder biomass is high. Overall, our findings suggest that continued increases in Flounder abundance coupled with the predicted long-term warming of ocean temperatures could have important implications for the predator-prey dynamics of Arrowtooth Flounder and juvenile pollock. The approach used in this study is valuable for identifying potential consequences of climate variability and exploitation on species spatial dynamics and interactions in many marine ecosystems.
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Climate and Demography Dictate the Strength of Predator-Prey Overlap in a Subarctic Marine Ecosystem
2013Co-Authors: Mary E Hunsicker, Lorenzo Ciannelli, Kevin M. Bailey, Stephani Zador, Leif Christian StigeAbstract:There is growing evidence that climate and anthropogenic influences on marine ecosystems are largely manifested by changes in species spatial dynamics. However, less is known about how shifts in species distributions might alter predator-prey overlap and the dynamics of prey populations. We developed a general approach to quantify species spatial overlap and identify the biotic and abiotic variables that dictate the strength of overlap. We used this method to test the hypothesis that population abundance and temperature have a synergistic effect on the spatial overlap of Arrowtooth Flounder (predator) and juvenile Alaska walleye pollock (prey, age-1) in the eastern Bering Sea. Our analyses indicate that (1) Flounder abundance and temperature are key variables dictating the strength of Flounder and pollock overlap, (2) changes in the magnitude of overlap may be largely driven by density-dependent habitat selection of Flounder, and (3) species overlap is negatively correlated to juvenile pollock recruitment when Flounder biomass is high. Overall, our findings suggest that continued increases in Flounder abundance coupled with the predicted long-term warming of ocean temperatures could have important implications for the predator-prey dynamics of Arrowtooth Flounder and juvenile pollock. The approach used in this study is valuable for identifying potential consequences of climate variability and exploitation on species spatia
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a probabilistic cellular automata approach for predator prey interactions of Arrowtooth Flounder atheresthes stomias and walleye pollock theragra chalcogramma in the eastern bering sea
Canadian Journal of Fisheries and Aquatic Sciences, 2012Co-Authors: Kun Chen, Kerim Aydin, Kevin M. Bailey, Kung-sik Chan, Lorenzo CiannelliAbstract:We developed a hybrid cellular automata (CA) modelling approach to explore the dynamics of a key predator- prey interaction in a marine system; our study is motivated by the quest for better understanding of the scale and heteroge- neity-related effects on the Arrowtooth Flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) dynam- ics during the summer feeding season in the eastern Bering Sea (EBS), but can be readily extended to other systems. The spatially explicit and probabilistic CA model incorporates individual behaviours and strategies and local interactions among species, as well as spatial and temporal heterogeneity due to geographical and (or) environmental changes in the physical environment. The model is hybridized, with an individual-based model (IBM) approach for increasing its capacity and con- tinuum and for balancing between computational efficiency and model validity, which makes it suitable for simulating pred- ator-prey dynamics in a large, complex ecological environment. We focus on the functional and aggregative responses of predators to prey density at different spatial scales, the effects of individual behaviours, and the impacts of systematic heter- ogeneity. Simulations from the model with suitable parameter values share qualitatively similar features found in field obser- vations, e.g., local aggregations around hydrographical features. Spatial heterogeneity is an important aspect of whether local-scale functional and aggregative responses reflect those operating over large, or global, scales. Resume : Nous avons mis au point une modelisation de type automate cellulaire (CA) hybride afin d'explorer la dyna- mique d'une interaction predateur-proie essentielle dans un systeme marin; notre etude cherche a mieux comprendre l'e- chelle et les effets associes a l'heterogeneite dans la dynamique de la plie a grande bouche (Atheresthes stomias )e t de la goberge de l'Alaska (Theragra chalcogramma) durant la saison estivale d'alimentation dans l'est de la mer de Bering (EBS); notre methodologie peut s'appliquer facilement a d'autres systemes. Le modele CA, qui est spatialement explicite et probabiliste, incorpore les comportements et les strategies individuels, les interactions locales entre les especes, de meme que l'heterogeneite spatiale et temporelle due aux changements geographiques et (ou) environnementaux dans le milieu phy- sique. Le modele est hybride avec un modele base sur l'individu (IBM) afin d'augmenter sa capacite et son continuum et pour etablir un equilibre entre l'efficacite informatique et la validite du modele, ce qui le rend approprie pour simuler la dy- namique predateur-proie dans un milieu ecologique complexe et de grande taille. Nous nous interessons particulierement aux reactions fonctionnelles et agregatives des predateurs en fonction de la densite des proies a differentes echelles spatiales, aux effets des comportements individuels et aux impacts de l'heterogeneite systematique. Les simulations produites par le modele avec des valeurs appropriees des parametres presentent des caracteristiques communes qualitativement semblables a celles observees sur le terrain, par ex., les agregations locales autour des structures hydrologiques. L'heterogeneite spatiale est un aspect important a considerer lorsqu'on veut determiner si les reactions fonctionnelles et agregatives observees a l'e- chelle locale representent bien celles qui agissent aux echelles plus larges ou globales. (Traduit par la Redaction)
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A probabilistic cellular automata approach for predator–prey interactions of Arrowtooth Flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) in the eastern Bering Sea
Canadian Journal of Fisheries and Aquatic Sciences, 2012Co-Authors: Kun Chen, Kerim Aydin, Kevin M. Bailey, Kung-sik Chan, Lorenzo CiannelliAbstract:We developed a hybrid cellular automata (CA) modelling approach to explore the dynamics of a key predator- prey interaction in a marine system; our study is motivated by the quest for better understanding of the scale and heteroge- neity-related effects on the Arrowtooth Flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) dynam- ics during the summer feeding season in the eastern Bering Sea (EBS), but can be readily extended to other systems. The spatially explicit and probabilistic CA model incorporates individual behaviours and strategies and local interactions among species, as well as spatial and temporal heterogeneity due to geographical and (or) environmental changes in the physical environment. The model is hybridized, with an individual-based model (IBM) approach for increasing its capacity and con- tinuum and for balancing between computational efficiency and model validity, which makes it suitable for simulating pred- ator-prey dynamics in a large, complex ecological environment. We focus on the functional and aggregative responses of predators to prey density at different spatial scales, the effects of individual behaviours, and the impacts of systematic heter- ogeneity. Simulations from the model with suitable parameter values share qualitatively similar features found in field obser- vations, e.g., local aggregations around hydrographical features. Spatial heterogeneity is an important aspect of whether local-scale functional and aggregative responses reflect those operating over large, or global, scales. Resume : Nous avons mis au point une modelisation de type automate cellulaire (CA) hybride afin d'explorer la dyna- mique d'une interaction predateur-proie essentielle dans un systeme marin; notre etude cherche a mieux comprendre l'e- chelle et les effets associes a l'heterogeneite dans la dynamique de la plie a grande bouche (Atheresthes stomias )e t de la goberge de l'Alaska (Theragra chalcogramma) durant la saison estivale d'alimentation dans l'est de la mer de Bering (EBS); notre methodologie peut s'appliquer facilement a d'autres systemes. Le modele CA, qui est spatialement explicite et probabiliste, incorpore les comportements et les strategies individuels, les interactions locales entre les especes, de meme que l'heterogeneite spatiale et temporelle due aux changements geographiques et (ou) environnementaux dans le milieu phy- sique. Le modele est hybride avec un modele base sur l'individu (IBM) afin d'augmenter sa capacite et son continuum et pour etablir un equilibre entre l'efficacite informatique et la validite du modele, ce qui le rend approprie pour simuler la dy- namique predateur-proie dans un milieu ecologique complexe et de grande taille. Nous nous interessons particulierement aux reactions fonctionnelles et agregatives des predateurs en fonction de la densite des proies a differentes echelles spatiales, aux effets des comportements individuels et aux impacts de l'heterogeneite systematique. Les simulations produites par le modele avec des valeurs appropriees des parametres presentent des caracteristiques communes qualitativement semblables a celles observees sur le terrain, par ex., les agregations locales autour des structures hydrologiques. L'heterogeneite spatiale est un aspect important a considerer lorsqu'on veut determiner si les reactions fonctionnelles et agregatives observees a l'e- chelle locale representent bien celles qui agissent aux echelles plus larges ou globales. (Traduit par la Redaction)
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recruitment forecast models for walleye pollock theragra chalcogramma fine tuned from juvenile survey data predator abundance and environmental phase shifts
Marine Ecology Progress Series, 2010Co-Authors: Tianyang Zhang, Kevin M. Bailey, Kung-sik ChanAbstract:Forecasting recruitment of marine fishes from environmental effects acting upon larvae has proven difficult due to multiple, nonlinear, interacting factors influencing larval survival. We used another approach, which circumvents the period of high egg and larval mortality, and instead improves forecasts from juvenile abundance indices. We compared several statistical recruitment forecast models and demonstrate that an increasing abundance of predators on juvenile walleye pol- lock Theragra chalcogramma, particularly the Arrowtooth Flounder Atheresthes stomias, which now dominates the groundfish biomass in the Gulf of Alaska, and autocorrelation caused by intercohort interactions strongly affect pollock recruitment during the juvenile phase. Furthermore, the weight of predictor variables changes with threshold criteria, which are linked to phase shifts in the marine environment. Our results indicate that forecasting recruitment of marine fishes can be improved by considering factors that influence survival after the juvenile period, but also needs to account for changes in community structure and phase shifts in the environment, as opposed to only environ- mental correlates. Inclusion of these factors is consonant with biological knowledge of the species.
Mark J. Bradburn - One of the best experts on this subject based on the ideXlab platform.
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Impact of light on catch rate of four demersal fish species during the 2009–2010 U.S. west coast groundfish bottom trawl survey
Fisheries Research, 2015Co-Authors: Mark J. Bradburn, Aimee A. KellerAbstract:Abstract To determine the influence of light on catch of demersal fish, we examined the relationship between near-bottom light levels, catch rates, and catch probability for four abundant groundfish species well represented in annual bottom trawl surveys on the U.S. west coast: Arrowtooth Flounder ( Atheresthes stomias ), greenstriped rockfish ( Sebastes elongatus ), longnose skate ( Raja rhina ), and Pacific hake ( Merluccius productus ). Relative downward irradiance was measured with MK-9 archival tags during annual trawl surveys along the U.S. west coast in 2009 and 2010. Near-bottom light levels were recorded for 818 hauls at depths less than 400 m. Significant linear relationships were observed between catch per unit effort (CPUE, kg ha −1 ) and near-bottom light ( P 10 light (μE m −2 s −1 ). CPUE of greenstriped rockfish increased 39% per unit increase in log 10 light. Light, depth, and latitude explained 15–47% of the variance in CPUE for the four species. Catch probability was significantly related to light, depth, latitude, and relative time of day ( P
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Shifts in condition and distribution of eastern North Pacific flatfish along the U.S. west coast (2003–2010)
Deep Sea Research Part I: Oceanographic Research Papers, 2013Co-Authors: Aimee A. Keller, Mark J. Bradburn, Victor H. SimonAbstract:Abstract Flatfish condition indices and distribution were examined along the U.S. west coast (55–1280 m) in relation to environmental variability and biomass using data from ten frequently occurring species collected in annual groundfish surveys from 2003 to 2010. The study was conducted during a period characterized by a cooling trend in the northern California Current system and by declining biomass for flatfish in general. Annual condition indices for six species (Arrowtooth Flounder, Dover sole, English sole, Pacific sanddab, petrale sole, and rex sole) were significantly related either to large-scale climatic indices (Pacific Decadal Oscillation, Multivariate El Nino–Southern Oscillation Index, North Pacific Gyre Oscillation) and/or annual biomass levels. Condition was most closely related to environmental effects rather than either biomass alone or both variables, with condition typically higher during cool climatic conditions. A similar analysis revealed that changes in distribution (measured as variation in annual catch-weighted mean latitude, longitude, depth and temperature) tended to be best described by models incorporating environmental effects and biomass rather than either variable alone. Linear trends in the center of distribution along a southeast–northwest axis were significant for seven species (Arrowtooth Flounder, deepsea sole, Dover sole, flathead sole, Pacific sanddab, petrale sole, and slender sole) with a tendency for flatfish to be displaced towards the southeast as environmental conditions shifted from warm to cooler conditions and biomass declined. A spatial distribution analysis indicated that for the majority of species (80%) the greatest magnitude of displacement (km) occurred when the centers of biomass were compared between environmental phases (average annual displacement 34 km) rather than changing biomass levels (average displacement 24 km). Taken together both approaches revealed that environmental changes and variation in biomass play significant roles in flatfish distribution.
Kung-sik Chan - One of the best experts on this subject based on the ideXlab platform.
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a probabilistic cellular automata approach for predator prey interactions of Arrowtooth Flounder atheresthes stomias and walleye pollock theragra chalcogramma in the eastern bering sea
Canadian Journal of Fisheries and Aquatic Sciences, 2012Co-Authors: Kun Chen, Kerim Aydin, Kevin M. Bailey, Kung-sik Chan, Lorenzo CiannelliAbstract:We developed a hybrid cellular automata (CA) modelling approach to explore the dynamics of a key predator- prey interaction in a marine system; our study is motivated by the quest for better understanding of the scale and heteroge- neity-related effects on the Arrowtooth Flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) dynam- ics during the summer feeding season in the eastern Bering Sea (EBS), but can be readily extended to other systems. The spatially explicit and probabilistic CA model incorporates individual behaviours and strategies and local interactions among species, as well as spatial and temporal heterogeneity due to geographical and (or) environmental changes in the physical environment. The model is hybridized, with an individual-based model (IBM) approach for increasing its capacity and con- tinuum and for balancing between computational efficiency and model validity, which makes it suitable for simulating pred- ator-prey dynamics in a large, complex ecological environment. We focus on the functional and aggregative responses of predators to prey density at different spatial scales, the effects of individual behaviours, and the impacts of systematic heter- ogeneity. Simulations from the model with suitable parameter values share qualitatively similar features found in field obser- vations, e.g., local aggregations around hydrographical features. Spatial heterogeneity is an important aspect of whether local-scale functional and aggregative responses reflect those operating over large, or global, scales. Resume : Nous avons mis au point une modelisation de type automate cellulaire (CA) hybride afin d'explorer la dyna- mique d'une interaction predateur-proie essentielle dans un systeme marin; notre etude cherche a mieux comprendre l'e- chelle et les effets associes a l'heterogeneite dans la dynamique de la plie a grande bouche (Atheresthes stomias )e t de la goberge de l'Alaska (Theragra chalcogramma) durant la saison estivale d'alimentation dans l'est de la mer de Bering (EBS); notre methodologie peut s'appliquer facilement a d'autres systemes. Le modele CA, qui est spatialement explicite et probabiliste, incorpore les comportements et les strategies individuels, les interactions locales entre les especes, de meme que l'heterogeneite spatiale et temporelle due aux changements geographiques et (ou) environnementaux dans le milieu phy- sique. Le modele est hybride avec un modele base sur l'individu (IBM) afin d'augmenter sa capacite et son continuum et pour etablir un equilibre entre l'efficacite informatique et la validite du modele, ce qui le rend approprie pour simuler la dy- namique predateur-proie dans un milieu ecologique complexe et de grande taille. Nous nous interessons particulierement aux reactions fonctionnelles et agregatives des predateurs en fonction de la densite des proies a differentes echelles spatiales, aux effets des comportements individuels et aux impacts de l'heterogeneite systematique. Les simulations produites par le modele avec des valeurs appropriees des parametres presentent des caracteristiques communes qualitativement semblables a celles observees sur le terrain, par ex., les agregations locales autour des structures hydrologiques. L'heterogeneite spatiale est un aspect important a considerer lorsqu'on veut determiner si les reactions fonctionnelles et agregatives observees a l'e- chelle locale representent bien celles qui agissent aux echelles plus larges ou globales. (Traduit par la Redaction)
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A probabilistic cellular automata approach for predator–prey interactions of Arrowtooth Flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) in the eastern Bering Sea
Canadian Journal of Fisheries and Aquatic Sciences, 2012Co-Authors: Kun Chen, Kerim Aydin, Kevin M. Bailey, Kung-sik Chan, Lorenzo CiannelliAbstract:We developed a hybrid cellular automata (CA) modelling approach to explore the dynamics of a key predator- prey interaction in a marine system; our study is motivated by the quest for better understanding of the scale and heteroge- neity-related effects on the Arrowtooth Flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) dynam- ics during the summer feeding season in the eastern Bering Sea (EBS), but can be readily extended to other systems. The spatially explicit and probabilistic CA model incorporates individual behaviours and strategies and local interactions among species, as well as spatial and temporal heterogeneity due to geographical and (or) environmental changes in the physical environment. The model is hybridized, with an individual-based model (IBM) approach for increasing its capacity and con- tinuum and for balancing between computational efficiency and model validity, which makes it suitable for simulating pred- ator-prey dynamics in a large, complex ecological environment. We focus on the functional and aggregative responses of predators to prey density at different spatial scales, the effects of individual behaviours, and the impacts of systematic heter- ogeneity. Simulations from the model with suitable parameter values share qualitatively similar features found in field obser- vations, e.g., local aggregations around hydrographical features. Spatial heterogeneity is an important aspect of whether local-scale functional and aggregative responses reflect those operating over large, or global, scales. Resume : Nous avons mis au point une modelisation de type automate cellulaire (CA) hybride afin d'explorer la dyna- mique d'une interaction predateur-proie essentielle dans un systeme marin; notre etude cherche a mieux comprendre l'e- chelle et les effets associes a l'heterogeneite dans la dynamique de la plie a grande bouche (Atheresthes stomias )e t de la goberge de l'Alaska (Theragra chalcogramma) durant la saison estivale d'alimentation dans l'est de la mer de Bering (EBS); notre methodologie peut s'appliquer facilement a d'autres systemes. Le modele CA, qui est spatialement explicite et probabiliste, incorpore les comportements et les strategies individuels, les interactions locales entre les especes, de meme que l'heterogeneite spatiale et temporelle due aux changements geographiques et (ou) environnementaux dans le milieu phy- sique. Le modele est hybride avec un modele base sur l'individu (IBM) afin d'augmenter sa capacite et son continuum et pour etablir un equilibre entre l'efficacite informatique et la validite du modele, ce qui le rend approprie pour simuler la dy- namique predateur-proie dans un milieu ecologique complexe et de grande taille. Nous nous interessons particulierement aux reactions fonctionnelles et agregatives des predateurs en fonction de la densite des proies a differentes echelles spatiales, aux effets des comportements individuels et aux impacts de l'heterogeneite systematique. Les simulations produites par le modele avec des valeurs appropriees des parametres presentent des caracteristiques communes qualitativement semblables a celles observees sur le terrain, par ex., les agregations locales autour des structures hydrologiques. L'heterogeneite spatiale est un aspect important a considerer lorsqu'on veut determiner si les reactions fonctionnelles et agregatives observees a l'e- chelle locale representent bien celles qui agissent aux echelles plus larges ou globales. (Traduit par la Redaction)
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recruitment forecast models for walleye pollock theragra chalcogramma fine tuned from juvenile survey data predator abundance and environmental phase shifts
Marine Ecology Progress Series, 2010Co-Authors: Tianyang Zhang, Kevin M. Bailey, Kung-sik ChanAbstract:Forecasting recruitment of marine fishes from environmental effects acting upon larvae has proven difficult due to multiple, nonlinear, interacting factors influencing larval survival. We used another approach, which circumvents the period of high egg and larval mortality, and instead improves forecasts from juvenile abundance indices. We compared several statistical recruitment forecast models and demonstrate that an increasing abundance of predators on juvenile walleye pol- lock Theragra chalcogramma, particularly the Arrowtooth Flounder Atheresthes stomias, which now dominates the groundfish biomass in the Gulf of Alaska, and autocorrelation caused by intercohort interactions strongly affect pollock recruitment during the juvenile phase. Furthermore, the weight of predictor variables changes with threshold criteria, which are linked to phase shifts in the marine environment. Our results indicate that forecasting recruitment of marine fishes can be improved by considering factors that influence survival after the juvenile period, but also needs to account for changes in community structure and phase shifts in the environment, as opposed to only environ- mental correlates. Inclusion of these factors is consonant with biological knowledge of the species.