Sub-topic 4.3 Aquatic food production systems

Base of aquatic food chains

photosynthesis by phytoplankton

Highest rates of aquatic productivity occur here

coastlines, shallow seas where upwellings and nutrient enrichment occur

Controversial species harvesting, e.g. seals and whales

ethical issues of biorights, rights of indigenous cultures and international conservation legislation

falling fish stocks and damage to habitats

developments in fishing equipment and changing methods of fishing

mitigation of unsustainable exploitation

policy, legislation and changes in consumer behaviour

aquaculture

the farming of marine and freshwater species which involves intervention in the rearing process to enhance production

aquaculture issues

loss of habitats, pollution from feed, fouling agents, antibiotics and other medicines added to fish pens, spread of disease, escaped species (GMOs)

wild fisheries

capture fisheries (harvesting fish in places where the population of a species occurs naturally)

"Improved" technology in fishing

improvements to boats, fishing gear (use of trawler bags), detection of fisheries via satellites and sonar

Management strategies for fisheries

quotas, designation of marine protected areas (exclusion zones), restriction of types and sizes of fishing gear (including mesh size of nets)

Types of fishing technology

Bottom trawling / dredging, gill nets, purse seine nets,

Bottom trawling/dredging

• collect shellfish such as oysters, scallops, or clams.

• dredge is pulled along the seafloor

• Dredging can be an effective method for commercial fishing

• environmental impacts: habitat destruction, disruption of seabed ecosystems.

Aquaculture techology

ponds/tanks, open pen nets

Maximum sustainable yield

Commercial fisheries use the concept of MSY (Maximum sustainably yield) to estimate how much fish they can take from the seas. It is the highest amount that can be taken each year without permanently decreasing the amount of natural capital.

Bad and rack system

Shellfish can be sustainably cultivated using "bag and rack" systems. These are exposed at low tide when they are able to be managed. They are "seeded" with young (juveniles) from hatcheries and don't require extra feed as they simply filter-feed.