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Biology LibreTexts

47.2C: Managing Fisheries

  • Page ID
    14252
  • Overfishing leads to fishery extinctions, loss of a food source, and affects many other species in ways that may be impossible to predict.

    LEARNING OBJECTIVES

    Explain the impact that the collapse of marine fisheries will have on human diet and health

    KEY TAKEAWAYS

    Key Points

    • Dramatic changes in species composition can result in an ecosystem shift, where species compositions differ from those that had been present before the depletion of the original fish stock.
    • In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction; if such trends continue, aquatic ecosystems could become unavailable as food sources.
    • Sustainable seafood is seafood from either fished or farmed sources that can maintain or increase production in the future without affecting the ecosystem in which it lives.

    Key Terms

    • sustainability: configuring society so that each can meet his own needs and greatest potential, while preserving biodiversity and natural ecosystems, and planning for future generations to maintain this potential.
    • overfishing: fishing that reduces an aquatic population, or stock, to a level that is inadequate for the stock to replenish itself

    Managing Wild Food Resources

    In addition to growing crops and raising animals for food, humans obtain food resources from wild populations, primarily fish populations. For approximately 1 billion people, aquatic resources provide the main source of animal protein. But since 1990, global fish production has declined dramatically. Despite considerable effort, few fisheries on the planet are managed for sustainability.

    Overfishing

    Overfishing is the harvest of an aquatic population to a level that is too low for that population to replenish itself. Resource depletion, low biological growth rates, and critically low biomass levels result from overfishing. For example, overfishing of sharks has disrupted entire marine ecosystems.

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    Overfishing: When a fish stock is reduced to a level that is too low to allow that stock to replenish itself, overfishing has occurred. In addition to eliminating major food sources, overfishing is a threat to aquatic biodiversity.

    The ability of a fishery to recover from overfishing depends on the species’ natural ability to replenish itself as well as the ecosystem’s conditions. Dramatic changes in species composition can result in an ecosystem shift, where other equilibrium energy flows involve species compositions different from those that had been present before overfishing occurred. For example, once trout have been overfished, carp might take over in a way that makes it impossible for the trout to re-establish a breeding population.

    Sustainable Ecosystem Management

    Fishery extinctions rarely lead to complete extinction of the harvested species, but rather to a radical restructuring of the marine ecosystem in which an abundant species is so over-harvested that it becomes a minor player, ecologically. In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction. In addition to humans losing the food source, these alterations affect many other species in ways that are difficult or impossible to predict. The collapse of fisheries has dramatic and long-lasting effects on local populations that work in the fishery. In addition, the loss of an inexpensive protein source to populations that cannot afford to replace it will increase the cost of living and limit societies in other ways. In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction. In addition to humans losing the food source, these alterations affect many other species in ways that are difficult or impossible to predict. The collapse of fisheries has dramatic and long-lasting effects on local populations that work in the fishery, not only the fishermen who depend directly on the fish stocks but all of the workers who are part of the industry, such as chefs, fish mongers, truck drivers, boat mechanics, and many more. In addition, the loss of an inexpensive protein source to populations that cannot afford to replace it can increase the cost of living and limit societies in other ways. The ultimate outcomes of overfishing and the commercial extinctions of fish stocks could include the loss of aquatic systems as food sources and economic crises for societies that depend on them.

    Sustainable seafood is a movement that has gained momentum as more people become aware of overfishing and environmentally-destructive fishing methods. Sustainable seafood is seafood from either fished or farmed sources that can maintain or increase production in the future without jeopardizing the ecosystems from which it was acquired. In general, slow-growing fish that reproduce late in life, such as orange roughy, are vulnerable to overfishing and are considered unsustainable seafood. Seafood species that grow quickly and breed young, such as anchovies and sardines, are much more resistant to overfishing and are therefore labeled “sustainable” and promoted as good alternatives.

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