4.3B Consumption of organisms from freshwater and marine environments Notes

Humans Consume Organisms from Freshwater and Marine Environments

1. Humans depend heavily on aquatic organisms, both flora (plants and algae) and fauna (fish, shellfish, and invertebrates), as essential food sources.
2. These foods contribute vital proteins, vitamins, minerals, and fatty acids that are crucial to human nutrition.
3. Consumption patterns differ across regions depending on cultural traditions, resource availability, and sustainability practices.

Examples of Aquatic Flora Consumed by Humans

Local Example - Watercress (Nasturtium officinale)

1. A freshwater plant commonly grown in Europe, especially the UK.
2. Cultivated in shallow streams or hydroponic systems with clean, flowing water.
3. Consumed raw in salads or cooked in soups.
4. Provides vitamins A, C, K, calcium, and antioxidants.

Global Example - Nori (Pyropia spp.)

1. A marine red alga cultivated in coastal Japan, Korea, and China.
2. Dried and pressed into thin sheets for sushi, snacks, and condiments.
3. Rich in iodine, iron, and proteins.
4. Plays an important role in global aquaculture exports.

Examples of Aquatic Fauna Consumed by Humans

Local Example - Queen Conch (Aliger gigas)

1. A large marine mollusk found in the Caribbean Sea and parts of the Atlantic.
2. Consumed as a delicacy in dishes like conch chowder or fritters.
3. Also harvested for its decorative pink shell, used in jewelry and souvenirs.
4. Populations have declined due to overharvesting, now protected under CITES Appendix II.

Global Example - Tilapia (Oreochromis niloticus)

1. A freshwater fish originally native to Africa, now farmed worldwide.
2. Commonly raised in aquaculture systems for its rapid growth and mild flavor.
3. A key source of affordable protein in Asia, Africa, and Latin America.
4. Represents one of the most farmed fish species globally due to low production costs.

Increasing Demand for Foods from Freshwater and Marine Environments

1. Global seafood demand is rising faster than population growth due to economic development, health awareness, and cultural globalization.
2. According to the FAO (2020), global fisheries and aquaculture reached a record 214 million tonnes, with aquaculture now producing over half of all seafood for human use.

Drivers of Increased Demand

1. Population Growth: More people require more protein-rich foods, increasing dependence on aquatic sources.
2. Rising Incomes and Urbanization: The expanding global middle class drives demand for premium seafood like tuna, salmon, and shrimp.
3. Changing Dietary Preferences: Shift toward “healthier” diets emphasizing omega-3 fatty acids and lean proteins.
4. Global Trade Expansion: Improved transportation and cold-chain logistics allow seafood to reach global markets efficiently.
5. Growth of Aquaculture: Aquaculture now supplies over half of all seafood consumed by humans, reducing pressure on wild stocks.

Evidence for Increasing Demand

1. Global seafood consumption rose from 9.0 kg per person per year (1961) to 20.5 kg (2019).
2. The growth rate of aquatic food consumption (3%) has been nearly double that of world population growth (1.6%).
3. Most of the increase is driven by urbanization and the rising middle class in Asia.

Unsustainable Harvesting

1. Overexploitation occurs when the rate of resource extraction exceeds the ecosystem’s capacity to regenerate.
2. In fisheries, this leads to declining stocks, habitat loss, and reduced biodiversity.
3. Unsustainable methods intensify the problem by damaging ecosystems directly.

Major Unsustainable Fishing Practices

1. Bottom Trawling

1. Involves dragging heavy nets across the seabed to catch benthic species (e.g., cod, flounder, shrimp).
2. Causes severe habitat destruction, sediment plumes, and carbon release.
3. Accounts for ~30 million tonnes of annual fish capture globally.
4. Banned in some regions (e.g., Venezuela; restricted zones in U.S. Pacific).

2. Ghost Fishing

1. Refers to lost or abandoned fishing gear (nets, traps) that continues to entangle marine life.
2. Caused by storms, poor disposal, or gear loss during trawling.
3. Affects over 136,000 marine mammals annually.
4. Each net can weigh several tonnes and persist for decades.

3. Use of Poisons and Explosives

1. Cyanide Fishing: Used to stun live fish for aquariums or restaurants. Kills coral and invertebrates.
2. Blast Fishing: Explosives used to stun or kill fish for easy collection. Common in Southeast Asia and coastal Africa.
3. Impacts:
   1. Destroys coral reefs and habitats.
   2. Kills non-target species.
   3. Only ~20% of fish killed are collected.

Overexploitation and Fishery Collapse

1. Overexploitation can lead to fishery collapse, when populations fall below recovery thresholds.
2. Collapsed fisheries disrupt food webs, economies, and local communities.

Global Overview and Implications

1. As of 2019, about 35% of global marine fisheries were overfished, and another 60% fully exploited.
2. Only 7% of fish stocks remain underfished.
3. Overfishing represents a tragedy of the commons, shared resources exploited without regulation lead to depletion for all.
4. Economic incentives drive overharvesting, but ecosystem-based management and sustainable quotas can help prevent further collapses.