Overfishing

Abstract: Introduction. 1. Elementary Dynamics of Exploited Populations. 1.1 The Logistic Growth Model. 1.2 Generalized Logistic Models: Depensation. 1.3 Summary and Critique. 2. Economic Models of Renewable-Resource Harvesting. 2.1 The Open-Access Fishery. 2.2 Economic Overfishing. 2.3 Biological Overfishing. 2.4 Optimal Fishery Management. 2.5 The Optimal Harvest Policy. 2.6 Examples Based on the Schaefer Model. 2.7 Linear Variational Problems. 2.8 The Possibility of Extinction. 2.9 Summary and Critique. 3. Capital-Theoretic Aspects of Resource Management. 3.1 Interest and Discount Rates. 3.2 Capital Theory and Renewable Resources. 3.3 Nonautonomous Models. 3.4 Applications to Policy Problems: Labor Mobility in the Fishery. 4. Optimal Control Theory. 4.1 One-Dimensional Control Problems. 4.2 A Nonlinear Fishery Model. 4.3 Economic Interpretation of the Maximum Principle. 4.4 Multidimensional Optimal Control Problem. 4.5 Optimal Investment in Renewable-Resource Harvesting. 5. Supply and Demand: Nonlinear Models. 5.1 The Elementary Theory of Supply and Demand. 5.2 Supply and Demand in Fisheries. 5.3 Nonlinear Cost Effects: Pulse Fishing. 5.4 Game-Theoretic Models. 5.5 Transboundary Fishery Resources: A Further Application of the Theory. 5.6 Summary and Critique. 6. Dynamical Systems. 6.1 Basic Theory. 6.2 Dynamical Systems in the Plane: Linear Theory. 6.3 Isoclines. 6.4 Nonlinear Plane-Autonomous Systems. 6.5 Limit Cycles. 6.6 Gause's Model of Interspecific Competition. 7. Discrete-Time and Metered Models. 7.1 A General Metered Stock-Recruitment Model. 7.2 The Beverton-Holt Stock-Recruitment Model. 7.3 Depensation Models. 7.4 Overcompensation. 7.5 A Simple Cohort Model. 7.6 The Production Function of a Fishery. 7.7 Optimal Harvest Policies. 7.8 The Discrete Maximum Principle. 7.9 Dynamic Programming. 8. The Theory of Resource Regulation. 8.1 A Behavioral Model. 8.2 Optimization Analysis. 8.3 Limited Entry. 8.4 Taxes and Allocated Transferable Quotas. 8.5 Total Catch Quotas. 8.6 Summary and Critique. 9. Growth and Aging. 9.1 Forestry Management: The Faustmann Model. 9.2 The Beverton-Holt Fisheries Model. 9.3 Dynamic Optimization in the Beverton-Holt Model. 9.4 The Case of Bounded F. 9.5 Multiple, Cohorts: Nonselective Gear. 9.6 Pulse Fishing. 9.7 Multiple Cohorts: Selective Gear. 9.8 Regulation. 9.9 Summary and Critique. 10. Multispecies Models. 10.1 Differential Productivity. 10.2 Harvesting Competing Populations. 10.3 Selective Harvesting. 10.4 A Diffusion Model: The Inshore-Offshore Fishery. 10.5 Summary and Critique. 11. Stochastic Resource Models. 11.1 Stochastic Dynamic Programming. 11.2 A Stochastic Forest Rotation Model. 11.3 Uncertainty and Learning. 11.4 Searching for Fish. 11.5 Summary and Critique. Supplementary Reading. References. Index.

Abstract: The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes—sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world's ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery.

Abstract: Contents. Preface. Acknowledgements. 1 Ecology and ecosystems. 1.1 Introduction. 1.2 Distribution and abundance. 1.2.1 Unit stocks. 1.2.2 Spacing of organisms. 1.3 Population growth and regulation. 1.3.1 Population growth. 1.3.2 Population regulation. 1.3.3 Life history patterns. 1.4 Marine ecosystems. 1.4.1 Coastal waters. 1.4.2 Coral reefs and lagoons. 1.4.3 Continental shelves and the open sea. 1.5 Human impacts on marine ecosystems. 1.5.1 Habitat modification and loss. 1.5.2 Eutrophication, siltation and heat. 1.5.3 Petroleum, toxic chemicals and solid waste. 1.5.4 Species invasions, introductions, and translocations. 1.5.5 Climate change - the greenhouse effect and global warming. 1.5.6 Ozone depletion. 1.5.7 Assessing and minimizing environmental impacts. 1.6 Photosynthetic marine organisms. 1.6.1 Macroalgae - seaweed. 1.6.2 Microalgae - phytoplankton. 1.6.3 Harmful algal blooms. 1.7 The flow of energy and material. 1.7.1 Zooplankton. 1.7.2 Daily migrations and the seasonal distribution of plankton. 1.7.3 Food relationships, trophic levels and foodwebs. 1.8 Productivity and fisheries. 1.8.1 Primary productivity and yield. 1.8.2 Productivity from fisheries and aquaculture. . 2 Exploited species. 2.1 Introduction. 2.2 Invertebrates. 2.2.1 Molluscs. Bivalves - clams and cockles. Gastropods - sea snails. Cephalopods - squids and octopuses. Management measures. 2.2.2 Crustaceans. Penaeids and carideans - prawns and shrimps. Nephropidae - clawed lobsters. Palinuridae - slipper and spiny lobsters. Brachyuran crabs. Anomuran crabs. Management measures. 2.2.3 Other invertebrates. Holothurians - sea cucumbers. Echinoids - sea urchins. Management measures. 2.3 Fishes. 2.3.1 Demersal fishes of cooler waters - cods, hakes and haddocks. 2.3.2 Demersal and reef fishes of warmer waters. 2.3.3 Coastal pelagic fishes - clupeoids. 2.3.4 Offshore pelagic fishes - tunas and sharks. 2.3.5 Management measures. 3 Fishing and fishers. 3.1 Introduction. 3.2 Fishing gear and methods. 3.2.1 Gleaning, spears and traps. 3.2.2 Hooks and lines. 3.2.3 Stationary nets. 3.2.4 Towed nets and dredges. 3.3 Fishers. 3.3.1 Fishing for food. 3.3.2 Fishing for income. 3.3.3 Fishing for recreation. 3.4 Effects of fishing. 3.4.1 Effects on target species. 3.4.2 Effects on non-target species. 3.4.3 Effects on the environment and ecosystems. . 4 Stock structure and abundance. 4.1 Introduction. 4.2 Structure and abundance. 4.2.1 Relative abundance. 4.2.2 Sampling surveys. 4.2.3 Mark-recapture methods. 4.2.4 Depletion methods. 4.3 Factors that increase biomass. 4.3.1 Size and growth. 4.3.2 Growth from length-frequency data. 4.3.3 Growth from tagging information. 4.3.4 Growth from hard-part analyses. 4.3.5 Reproduction. 4.3.6 Recruitment. 4.4 Factors that decrease biomass. 4.4.1 Age-based catch curves. 4.4.2 Length-based catch curves. 4.4.3 Mortality from mark-recapture data. 4.4.4 Natural mortality. 5 Stock assessment. 5.1 Introduction. 5.2 Stock abundance and catches - dynamic production models. 5.2.1 Equilibrium models. 5.2.2 Non-equilibrium models. 5.2.3 Multispecies applications. 5.2.4 Potential yield - rough estimators. 5.3 Including growth and mortality. 5.3.1 The effects of growth and mortality on biomass. 5.3.2 The effects of fishing mortality on a single cohort. 5.4 Including different year classes age-structured models. 5.4.1 Virtual population analysis. 5.4.2 The classical yield per recruit model. 5.4.3 The Thompson and Bell model. 5.5 Simulation and ecosystem models. 5.5.1 A biomass dynamic simulation model. 5.5.2 An age-structured simulation model. 5.5.3 Ecosystem models. 5.5.4 Risk assessment. 6 Fisheries management. 6.1 Introduction. 6.2 The need for fisheries management. 6.2.1 Biological overfishing. 6.2.2 Economic overfishing. 6.3 Managers and stakeholders. 6.3.1 Fisheries management authorities. 6.3.2 Co-management in commercial fisheries. 6.3.3 Community-based fisheries management. 6.4 The management process. 6.4.1 Management policies and objectives. 6.4.3 Reference points and indicators. 6.4.4 Management plans. 6.5 Management actions. 6.5.1 Input controls (on fishing and fishing effort). Limiting the number of fishing units. Limiting the efficiency and types of fishing gear. Minimum mesh sizes and escape gaps. 6.5.2 Output controls (on the catch). Quotas. Size limits. Rejection of females or gravid females. 6.5.3 Controls to protect the ecosystem. Closures as fisheries management tools. 6.5.4 Compliance and enforcement. References. Appendices. 1. Fisheries symbols and formulae. 2. Standard deviation and confidence limits. 3. Correlation and regression. 4. Least squares. 5. Collection of length-frequency data. 6. Bhattacharya plots. 7. Statistical tables. Glossary of terms. Index