Unsustainable Harvesting Practices & Overexploitation (DP IB Environmental Systems & Societies (ESS))

Unsustainable Harvesting Practices

• The rising global demand for seafood has led to the use of unsustainable harvesting practices

  • These methods often damage marine ecosystems and lead to overexploitation of fish stocks

1. Bottom trawling:

   • This method involves dragging heavy nets along the seabed

   • Impacts:

     • Destroys habitats such as coral reefs

     • Results in significant bycatch (catching non-target species)

     • Disturbs sediment, causing sediment pollution and releasing other trapped pollutants

2. Ghost fishing:

   • This occurs when abandoned or lost fishing gear continues to catch marine life

     • E.g. ghost nets

   • Impacts:

     • Continues to catch fish and other marine animals, leading to unnecessary deaths

     • Causes entanglement of marine organisms, including endangered species

     • Contributes to marine debris and pollution

3. Use of poisons:

   • Some fishermen use poisons and toxic substances, such as cyanide, to stun or kill fish, making them easier to catch

   • Impacts:

     • Poisons kill or damage a wide range of marine life

     • Cyanide kills coral polyps and other organisms that form the coral reef structure, leading to reef degradation and overall loss of biodiversity

     • This method is highly unsustainable and illegal in many places

4. Use of explosives:

   • Some fishermen use explosives, such as dynamite, to stun or kill fish, making them easier to catch

   • Impacts:

     • Explosives destroy marine habitats and kill indiscriminately (kill non-target species)

     • Causes extensive damage to coral reefs and other important marine habitats

     • This method is also highly unsustainable and illegal in many places

Overexploitation

• Developments in fishing equipment and increased use of unsustainable fishing methods have led to declining fish stocks and damage to habitats

  • Fish stocks in the oceans are rapidly decreasing in size

  • This is mainly due to overfishing

• Overexploitation happens when fish are harvested at a rate faster than they can reproduce

  • This can eventually lead to the collapse of fisheries, where the fish population drops so low that it cannot recover

Maximum Sustainable Yield

• The annual yield for a natural resource (such as a forest) is the annual gain in biomass or energy, through growth

• The maximum sustainable yield (MSY) is the maximum amount of a renewable natural resource that can be harvested annually without compromising the long-term productivity of the resource

• It is the level of harvest that can be maintained indefinitely

• The concept of maximum sustainable yield applies to various resources, such as crops, fish, timber, and game animals

  • For example, in fisheries, the concept of maximum sustainable yield is used to determine the maximum amount of fish that can be harvested sustainably from a given population

  • This is calculated based on the population size, growth rate and reproduction rate

  • If the fishing rate exceeds the maximum sustainable yield, the population may decline, and the long-term productivity of the fishery may be affected

• In summary, the maximum sustainable yield is the highest possible annual catch that can be sustained over time without depleting the fish stock

• Calculating the maximum sustainable yield is important as it helps in setting appropriate limits on fishing quotas to ensure sustainable fishing practices

Many fisheries still operate above the maximum sustainable yield, leading to continued overexploitation—this is because the fishing is still profitable in the short-term, even if in the long-term the stock will be depleted to the point where fishing is no longer commercially viable