This paper analyzes the trophic role of Pacific herring, the potential consequences of its deplet... more This paper analyzes the trophic role of Pacific herring, the potential consequences of its depletion, and the impacts of alternative herring fishing strategies on a Northeast Pacific food web in relation to precautionary, ecosystem-based management. We used an Ecopath with Ecosim ecosystem model parameterized for northern British Columbia (Canada), employing Ecosim to simulate ecosystem effects of herring stock collapse. The ecological impacts of various herring fishing strategies were investigated with a Management Strategy Evaluation algorithm within Ecosim, accounting for variability in climatic drivers and stock assessment errors. Ecosim results suggest that herring stock collapse would have cascading impacts on much of the pelagic food web. Management Strategy Evaluation results indicate that herring and their predators suffer moderate impacts from the existing British Columbia harvest control rule, although more precautionary management strategies could substantially reduce th...
We present a comprehensive analysis of estimation of fisheries Maximum Sustainable Yield (MSY) re... more We present a comprehensive analysis of estimation of fisheries Maximum Sustainable Yield (MSY) reference points using an ecosystem model built for Mille Lacs Lake, the second largest lake within Minnesota, USA. Data from single-species modelling output, extensive annual sampling for species abundances, annual catch-survey, stomach-content analysis for predatory-prey interactions, and expert opinions were brought together within the framework of an Ecopath with Ecosim (EwE) ecosystem model. An increase in the lake water temperature was observed in the last few decades; therefore, we also incorporated a temperature forcing function in the EwE model to capture the influences of changing temperature on the species composition and food web. The EwE model was fitted to abundance and catch time-series for the period 1985 to 2006. Using the ecosystem model, we estimated reference points for most of the fished species in the lake at single-species as well as ecosystem levels with and without...
The Cartesian coordinates of fish schooling in aquarium tanks are estimated by combining a perisc... more The Cartesian coordinates of fish schooling in aquarium tanks are estimated by combining a periscope image via mirrors with a direct view on one photograph. Systematic errors from simple geometrical estimates based on parallax are accurately compensated by calibration using multiple polynomial regression. Once calibration has been carried out, the periscope method has advantages over others in using standard photographic equipment, in reducing measuring time, and in the identification of fish.
An investigation of illegal and unreported fishing in source countries indicates that 24–36% of 2... more An investigation of illegal and unreported fishing in source countries indicates that 24–36% of 2.15 million tonnes of wild-seafood imports to Japan in 2015 were of illegal and unreported origin, valued at $1.6 to $2.4 billion, out of a total import of US$ 13 billion. A supply chain case study of crab imported from Russia illustrates the intricacies of trade in illegal seafood products in this region. Weakly framed import regulations and outdated fisheries policies appear to be driving an inadvertent trade of illegal and unreported seafood products into the Japanese market. A multilateral approach could extend the strict requirements for food safety to the country of origin and provide more complete supply chain traceability for all commercial seafood species imported by Japan.
For estimating age-group parameters from size-frequency data, conventional efficient statistical ... more For estimating age-group parameters from size-frequency data, conventional efficient statistical methods, such as maximum likelihood, can be more effective than the commonly used graphical methods of dissecting a mixed distribution. Fisheries size-frequency data are usually grouped over size intervals and the efficient methods are easily programmed on a computer for this case. We show that several published alternatives offer no computational advantages over our method. We describe an interactive computer program that assists the user in determining which parameters may be estimated from a set of data. The program alternates between constrained direct-search optimization and fast iterative calculations. Two examples of fisheries length-frequency data show that fitting is made easier by employing a subsample aged by biological methods for the preliminary starting values of parameters, and that the best fit may involve a trade-off between statistical precision and biological plausibil...
... Tony J. Pitcher (pitcher.t@gmail.com) is Professor of Fisheries, Fisheries Centre, Aquatic Ec... more ... Tony J. Pitcher (pitcher.t@gmail.com) is Professor of Fisheries, Fisheries Centre, Aquatic Ecosystems Research Laboratory, University of British ... Rumble III Gothic Morgue Graveyard Capricorn Davidson Cobb Bowie Acores Condor PAL Sedlo Voador DJ Castro Great Meteor ...
Page 1. Chapter six Beyond the status quo: rethinking fishery management Anthony T. Charles ABSTR... more Page 1. Chapter six Beyond the status quo: rethinking fishery management Anthony T. Charles ABSTRACT This chapter explores several controversial challenges for fishery manage-ment of the future. First, emphasis is placed ...
The authors of several recent texts on sociobiology (Dawkins 1976; Wilson 1975; Edmunds 1974) hav... more The authors of several recent texts on sociobiology (Dawkins 1976; Wilson 1975; Edmunds 1974) have assumed that the "stotting" behavior of Thomson's gazelle and other antelopes puts the animal at greater risk from attacking predators, such as lions or hunting dogs, than a ...
Conflict of interest among fishers characterizes most fisheries and leads to competition for the ... more Conflict of interest among fishers characterizes most fisheries and leads to competition for the resource. This puts a premium on present actions and discounts the future. As a result, most common-property fisheries inexorably move toward overexploitation. This chapter proposes ...
This paper analyzes the trophic role of Pacific herring, the potential consequences of its deplet... more This paper analyzes the trophic role of Pacific herring, the potential consequences of its depletion, and the impacts of alternative herring fishing strategies on a Northeast Pacific food web in relation to precautionary, ecosystem-based management. We used an Ecopath with Ecosim ecosystem model parameterized for northern British Columbia (Canada), employing Ecosim to simulate ecosystem effects of herring stock collapse. The ecological impacts of various herring fishing strategies were investigated with a Management Strategy Evaluation algorithm within Ecosim, accounting for variability in climatic drivers and stock assessment errors. Ecosim results suggest that herring stock collapse would have cascading impacts on much of the pelagic food web. Management Strategy Evaluation results indicate that herring and their predators suffer moderate impacts from the existing British Columbia harvest control rule, although more precautionary management strategies could substantially reduce th...
We present a comprehensive analysis of estimation of fisheries Maximum Sustainable Yield (MSY) re... more We present a comprehensive analysis of estimation of fisheries Maximum Sustainable Yield (MSY) reference points using an ecosystem model built for Mille Lacs Lake, the second largest lake within Minnesota, USA. Data from single-species modelling output, extensive annual sampling for species abundances, annual catch-survey, stomach-content analysis for predatory-prey interactions, and expert opinions were brought together within the framework of an Ecopath with Ecosim (EwE) ecosystem model. An increase in the lake water temperature was observed in the last few decades; therefore, we also incorporated a temperature forcing function in the EwE model to capture the influences of changing temperature on the species composition and food web. The EwE model was fitted to abundance and catch time-series for the period 1985 to 2006. Using the ecosystem model, we estimated reference points for most of the fished species in the lake at single-species as well as ecosystem levels with and without...
The Cartesian coordinates of fish schooling in aquarium tanks are estimated by combining a perisc... more The Cartesian coordinates of fish schooling in aquarium tanks are estimated by combining a periscope image via mirrors with a direct view on one photograph. Systematic errors from simple geometrical estimates based on parallax are accurately compensated by calibration using multiple polynomial regression. Once calibration has been carried out, the periscope method has advantages over others in using standard photographic equipment, in reducing measuring time, and in the identification of fish.
An investigation of illegal and unreported fishing in source countries indicates that 24–36% of 2... more An investigation of illegal and unreported fishing in source countries indicates that 24–36% of 2.15 million tonnes of wild-seafood imports to Japan in 2015 were of illegal and unreported origin, valued at $1.6 to $2.4 billion, out of a total import of US$ 13 billion. A supply chain case study of crab imported from Russia illustrates the intricacies of trade in illegal seafood products in this region. Weakly framed import regulations and outdated fisheries policies appear to be driving an inadvertent trade of illegal and unreported seafood products into the Japanese market. A multilateral approach could extend the strict requirements for food safety to the country of origin and provide more complete supply chain traceability for all commercial seafood species imported by Japan.
For estimating age-group parameters from size-frequency data, conventional efficient statistical ... more For estimating age-group parameters from size-frequency data, conventional efficient statistical methods, such as maximum likelihood, can be more effective than the commonly used graphical methods of dissecting a mixed distribution. Fisheries size-frequency data are usually grouped over size intervals and the efficient methods are easily programmed on a computer for this case. We show that several published alternatives offer no computational advantages over our method. We describe an interactive computer program that assists the user in determining which parameters may be estimated from a set of data. The program alternates between constrained direct-search optimization and fast iterative calculations. Two examples of fisheries length-frequency data show that fitting is made easier by employing a subsample aged by biological methods for the preliminary starting values of parameters, and that the best fit may involve a trade-off between statistical precision and biological plausibil...
... Tony J. Pitcher (pitcher.t@gmail.com) is Professor of Fisheries, Fisheries Centre, Aquatic Ec... more ... Tony J. Pitcher (pitcher.t@gmail.com) is Professor of Fisheries, Fisheries Centre, Aquatic Ecosystems Research Laboratory, University of British ... Rumble III Gothic Morgue Graveyard Capricorn Davidson Cobb Bowie Acores Condor PAL Sedlo Voador DJ Castro Great Meteor ...
Page 1. Chapter six Beyond the status quo: rethinking fishery management Anthony T. Charles ABSTR... more Page 1. Chapter six Beyond the status quo: rethinking fishery management Anthony T. Charles ABSTRACT This chapter explores several controversial challenges for fishery manage-ment of the future. First, emphasis is placed ...
The authors of several recent texts on sociobiology (Dawkins 1976; Wilson 1975; Edmunds 1974) hav... more The authors of several recent texts on sociobiology (Dawkins 1976; Wilson 1975; Edmunds 1974) have assumed that the "stotting" behavior of Thomson's gazelle and other antelopes puts the animal at greater risk from attacking predators, such as lions or hunting dogs, than a ...
Conflict of interest among fishers characterizes most fisheries and leads to competition for the ... more Conflict of interest among fishers characterizes most fisheries and leads to competition for the resource. This puts a premium on present actions and discounts the future. As a result, most common-property fisheries inexorably move toward overexploitation. This chapter proposes ...
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