4.3 Aquatic Food Production Systems Aquatic systems provide a source of food production Unsustainable use of aquatic ecosystems can lead to environmental degradation and collapse of wild fisheries Aquaculture provides potential for increased food production

Marine Ecosystem and Food Web Photosynthesis by phytoplankton supports a highly diverse range of food webs The highest rates of productivity are found near coastlines or in shallow seas where upwelling and nutrient enrichment of surface waters occurs

Upwelling When cold nutrient-rich waters come up from the ocean depths Normally ocean productivity is low due to limiting factors (sunlight and nutrients) Dead organisms sink to bottom

El Nino Southern Oscillation Occur every few years ENSO’s occur when the prevailing westerly winds weaken or cease and surface waters along the South and North American Coasts become warmer Upwellings of cold nutrient rich waters are suppressed Leads to declines in fish populations

Fisheries Industrial Farming and Hunting Demand is high and rising 90% in the oceans and 10% in freshwater Includes wild fisheries and aquaculture More than 70% of the world’s fisheries are fully exploited, in decline or too low to allow for recovery Demand is high and rising High in protein, low in saturated fats and contain vitamins A,B,D that humans need for healthy diet MEDCs are becoming more health conscious

Methods of fishing Developments in fishing equipment and changes to fishing methods have led to dwindling fish stocks and damage to habitats Harvesting some species (seals and whales) can be controversial Ethical issues arise over biorights, rights of indigenous cultures (Inuit) and international conservation legislation

Dredging Dredges are large, metal-framed baskets that are dragged across the seafloor to collect shellfish like oysters, clams and scallops. In order to lift the catch into the basket, metal teeth dig into the seafloor, which can significantly impact seafloor habitat and bottom-dwelling species.

Gillnets Gillnetting uses curtains of netting that are suspended by a system of floats and weights; they can be anchored to the seafloor or allowed to float at the surface. The netting is almost invisible to fish, so they swim right into it. Gill nets are often used to catch sardines, salmon and cod, but can accidentally entangle and kill other animals, including sharks and sea turtles.

Trawling A bottom trawl is a type of fishing net that's pulled along the seafloor. Fishermen commonly use bottom trawls to catch shrimp and bottom-dwelling fish like halibut and sole. However, in addition to these target fish, the nets also catch a variety of ocean life that's usually thrown back dead or dying. Dragging heavy gear across the seabed can also damage sensitive seafloor habitat.

Longlining Longlining employs a central fishing line that can range from one to 50 miles long; this line is strung with smaller lines of baited hooks, dangling at evenly spaced intervals. Longlines can be set near the surface to catch pelagic fish like tuna and swordfish, or laid on the seafloor to catch deep-dwelling fish like cod and halibut. Many lines, however, can hook sea turtles, sharks and seabirds that are also attracted to the bait.

Maximum sustainable yield The highest amount that can be taken without permanently depleting the stock How many fish and of what size can be taken in any year so the harvest is not impaired in subsequent years Generally MSY is about ½ the carrying capacity of an organism (fishing quotas set below that)

Strategies to avoid unsustainable fishing Unsustainable exploitation of aquatic systems can be mitigated at a variety of levels (International, national, local and individual) through policy, legislation and changes in human behavior Improvements to boats and fishing gear Detection of fisheries and boats via satellites Use of quotas Designation of marine protected areas Restriction on types and sizes of fishing gear (including mesh size of nets) Aquaculture has grown to provide additional food resources and support economic development and is expected to continue to rise

Aquaculture Advantages: Disadvantages: Loss of habitats Pollution Accounts for over 50% of world market for fish Takes stress off ocean fisheries Becoming more sustainable Efficient means of protein production Disadvantages: Loss of habitats Pollution Feed, antibiotics and other medicine added to fish pens Spread of diseases Escaped species (some genetically modified organisms)

Hatchery Hatchery fish are bred and reared in nurseries, either for use in aquaculture or to be released and caught in wild-capture fisheries. When released in large numbers, hatchery-raised fish can compete with wild populations for food. There are also concerns about genetically weaker hatchery fish interbreeding with and threatening the viability of wild populations.

Open Net Pens or Cages Open net pens or cages enclose fish such as salmon in offshore coastal areas or in freshwater lakes. Net pens are considered a high-impact aquaculture method because waste from the fish passes freely into the surrounding environment, polluting wild habitat. Farmed fish can also escape and compete with wild fish for natural resources or interbreed with wild fish of the same species, compromising the wild population. Diseases and parasites can also spread to wild fish living near or swimming past net pens.

Ponds Ponds enclose fish in a coastal or inland body of fresh or salt water. Shrimp, catfish and tilapia are commonly raised in this manner. Wastewater can be contained and treated. However, the discharge of untreated wastewater from the ponds can pollute the surrounding environment and contaminate groundwater. Moreover, the construction of shrimp ponds in mangrove forests has destroyed more than 3.7 million acres of coastal habitat important to fish, birds and humans.

Recirculating systems Recirculating systems raise fish in tanks in which water is treated and recycled through the system. Almost any finfish species such as striped bass, salmon and sturgeon can be raised in recirculating systems. Recirculating systems address many environmental concerns associated with fish farming—fish cannot escape, and wastewater is treated—but they are costly to operate and rely on electricity or other power sources.

China’s Aquaculture China produces 62% of all farmed fish worldwide Some (carp and catfish) grown in rice paddies Waste provides fertilizer for rice

International Conflict The ”cod wars” were a series of disputes between Britain and Iceland running from the 1950s to the 1970s over the rights to fish in Icelandic waters. Turbot (halibut) war between Canada and Spain in 1995 when Canada fired on a Spanish fishing boat and chased it out of Canadian waters. Growing tension between India and Sri Lanka in 2012. Over 100 Indian fisherman killed and 350 seriously injured because of fishing along Sri Lankan coast This year China has increased their fishing fleet to over 2000 percent. In the past decade they have had conflict for fishing in the waters of Indonesian, the Philippines, Japanese, Korean and Russian.