Summary of topic 4.3
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Aquatic food production systems provide many food sources for human consumption including algae, fish, shellfish, and other organisms. These systems face sustainability challenges due to overexploitation from fishing and environmental impacts from aquaculture. Effective management strategies like catch limits, marine protected areas, and regulating farm practices are needed to support long-term viability of aquatic food resources.
Summary of topic 4.3
- 1. Topic 4 Water and aquatic food production systems and societies 4.3 Aquatic food production systems
- 2. Aquatic Food Production • Algae – human food source, agar gels (around 30 million tonnes/yr harvested, largely in SE Asia) • Fish – human consumption, animal/pet food, fish oil, food for aquaculture, gelatin, fertilisers (approx 20kg/capita/yr worldwide and increasing) • Shellfish – mollusks (e.g. scallops), crustaceans (e.g. shrimp, lobsters) • Others – reptiles (e.g. turtles, crocodiles, alligators), amphibians (e.g. frogs), mammals (e.g. whales, dolphins, seals)
- 3. Food Prices • World food prices have been increasing recently • There is increasing meat and fish consumption in MEDCs and LEDCs • More staple crops and fish are being used as animal feed • Also more farmland is being used to grow biofuels (especially in Brazil) - Land is becoming more expensive and more limited • World oil prices are unstable and transportation costs are therefore increasing World Food Price Index
- 4. Terrestrial and Aquatic Systems • In MEDCs we generally want a large variety of foods, and this also gives a more healthy diet • This is leading to greater demand for meat and fish • Also driven by rising human population and changes in population demographics • Terrestrial farming (e.g. arable and herbivore farming) harvests low trophic levels • Aquatic farming (e.g. fish farming) generally harvests high trophic levels • The Second Law of Thermodynamics shows that more energy must be put into an aquatic system to harvest the same amount of biomass
- 5. Terrestrial and Aquatic Systems
- 6. Sea Fisheries and Sustainability • Mostly occurs near the coast. Bigger stocks since more nutrients available from river discharge and upwelling (caused by strong winds and coastal currents) • Fisheries are only sustainable if the rate of removal < growth rate • However, most major fisheries are now over-exploited • The maximum sustainable yield occurs where population is increasing at its maximum rate MSY Above MSY, yield is reduced by competition for resources Below MSY, yield is decreased due to the small population Fishing techniques
- 7. Sea Fisheries and Sustainability • There are 2 major problems which prevent global sustainability: – The Tragedy of the Commons – Every country (and individual fishermen) wants to catch fish in their own territorial waters before the stocks leave and head to those of another country. – Short-term gain – It is easy (and tempting) to see the greatest gain over the short term rather than look towards long-term conservation of stocks
- 8. Sea Fisheries and Sustainability • Possible conservation strategies include: • Reduce the size of fishing fleets • Reduce the size of individual fishing boats • Reduce net/mesh size (this helps to prevent juvenile fish being caught which can then spawn) • Closed seasons • Exclusion zones/Marine Protective Areas (these conserve habitats and allow fish to spawn) The Downeaster Alexa
- 9. Case Study 1 - Newfoundland • Before 1950, the largest cod stocks in the world • From 1950s onwards introduction of technology to exploit the stocks commercially • Fishing peaked in 1968 – 800 000 tonnes • The local and national government did not intervene for fear of affecting jobs • The entire fishery collapsed • In 1992 it was closed completely, leading to the loss of 42 000 jobs • It still hasn’t recovered Newfoundland cod fishery collapse
- 10. Case Study - Newfoundland
- 11. Case 2 - Iceland • Most important industry in the country is cod fishing • Stocks began to decline in the early 1950s, but the government decided to take action • They protected and expanded their territorial waters aggressively. This lead to confrontations with the British Navy between 1952 and 1976 (The ‘Cod Wars’ *) • Restrictions were introduced on fleet size, boat sizes, fishing gear and mesh size • Introduction of closed seasons • Use of coast guard and inspectors to enforce restrictions * Won by Iceland after it threatened to leave NATO The Cod Wars
- 12. Marine Hunting • Includes hunting of seals, dolphins and whales • In the Western World this is largely seen as unethical – Marine mammals seen as intelligent and close relatives of humans – Many hunting methods seen as causing unnecessary pain, e.g. harpooning or clubbing – Some species have been driven close to extinction – Hunting of fur seals involves killing juvenile animals • However hunting may play an important role in many indigenous communities, e.g. Inuit
- 13. Aquaculture • This is the farming of aquatic species (marine and freshwater) • Not just as a food source. Also for commercial products, pets, skins etc. • Fish, shellfish, reptiles and amphibians all farmed • Aquaculture is increasing as fisheries are declining (due to over-exploitation) • Includes open systems and closed systems • Open systems are created by caging species in an existing habitat (riverine or coastal) • Closed systems are created in tanks situated inland
- 14. Environmental Impacts of Aquaculture • Loss of habitats, e.g. mangroves, to be replaced with closed systems (e.g. caged fish or shrimp) • Generation of sediments (from faeces), smothering benthic habitats and creating anoxic conditions • Generation of nutrients (from faeces) creating algal blooms and eutrophication of freshwater • Contamination of with antibiotics and hormones • Pollution caused by antifouling paints which contain toxins including heavy metals • Spread of disease in densely-packed populations • Escape of farmed animals (may outcompete or prey on indiginous species) • Attraction of predators which may become trapped in cages