Fish Farming: Intro to Aquaculture Methods, Pro’s and Con’s

History Fish are a vital component of the human diet - nearly half the world’s population gets the majority of its protein from seafood As population increases, so does demand for seafood… But Many species - perhaps 70% or more - have been fished to their sustainable limits or beyond. Fish stocks are declining

Why are our fish stocks declining? Overfishing: Bigger fishing vessels Better technology to find fish Better nets Higher demand Lag time in population drop FAO State of World Fisheries and Aquaculture (SOFIA) – 2006 http://www.fao.org/DOCREP/007/y5600e/y5600e00.htm

Question What do we do?

The answer: Aquaculture? Proponents of fish farming say that the industry not only supplies an important food resource, it also benefits wild stocks by reducing fishing pressures. However, Many fishermen and environmentalists disagree claim that aquaculture can degrade the habitat, health, and genetic vigor of wild species

Salmon Debate Farm-raised Salmon Wild Salmon Survival rate from egg to adult of 1-2% Declining wild populations due to overfishing and habitat degradation Live and dead fish important part of stream and ocean food chains Seabirds and marine mammals caught and killed during fishing activities No dyes, no antibitoics, healthier Survival rate from egg to adult of 80-90% Concentrated waste cause algal blooms and low oxygen ‘dead zones’ Higher levels of pollutants in tissues Less expensive and more widely available to consumers Color from dyes, feed antibiotics, fewer essential fatty acids and oils

Types of Aquaculture

Open net pens or cages Anchored in offshore coastal areas Pro’s: Salmon, tuna Pro’s: Cheap no by-catch does not deplete wild stocks Con’s: Waste passes to environment Escapees Disease & parasites http://www.ambhanoi.um.dk/NR/rdonlyres/92ADABED-4F6A-4F6A-A04D-2A83242C1687/0/aquaculture3.jpg

Ponds Manmade ponds, recirculating seawater Pro’s: Con’s: Shrimp, catfish, tilapia Pro’s: Cheap no by-catch does not deplete wild stocks Provides jobs Con’s: Location of ponds can destroy important habitat (mangroves) Untreated water contaminates local environment But, it CAN be treated http://www.biology.duke.edu/bio217/2005/ncm3/pond_liner.gif

Raceways Divert water from a waterway Pro’s: Con’s: Must be treated before being released back to waterway Rainbow trout Pro’s: no by-catch does not deplete wild stocks Provides jobs Con’s: Can be costly to build Untreated water Escapees (invasive species) http://www.lib.noaa.gov/korea/korean_aquaculture/raceway.files/baqbk001.jpeg

Recirculating Systems Enclosed tanks Water is cleaned & reused Striped bass, salmon, sturgeon Environmentally sound Pro’s Can help rebuild wild populations Provides jobs Conserves wild stocks Con’s Requires a lot of energy and thus $$ http://www.ag.auburn.edu/fish/image_gallery/data/media/77/Recirc_Kent_Seatech_jpg.jpg

Shellfish Culture Ropes, plastic trays, mesh bags Pro’s Problems: Shellfish require only clean water to survive Pro’s Easy to do Can clean up nutrient rich water Protects wild populations Problems: Waste accumulation disease http://www.whoi.edu/cms/images/oceanus/2005/6/v43n1-kitepowell3en_10837.jpg

Why should we bother? Food Long term economics Overfishing correlates with: Low biodiversity in the environment Harmful algal blooms Beach closures Darker color = more protein obtained from seafood

Why should we bother? While some recover after collapse, many do not (or at least, have not) Cod Atlantic Bluefin tuna Pacific Northwest Salmon There used to be wars over Atlantic cod, now they are almost gone…. http://www.codgen.olsvik.info/cDNA%20libraries.html

Seafood Choices

The Promise and Perils of Fish Farming http://www.edf.org/page.cfm?tagID=16150

Issue: Imported Fish The seafood Americans eat largely comes from abroad Problem: many nations that supply us with farmed fish do not adequately regulate these operations Solution: policymakers and fish farmers worldwide need to implement strong standards for aquaculture operations

Issue: Economic and ecological damage Some fish farming does economic and ecological damage in the long run example, in Thailand, Ecuador and many other tropical nations, coastal forests of mangroves were cut down in the past and replaced with shrimp farms. Water degrades and farm closes: no farm OR mangrove Problem: unregulated aquaculture can destroy ecological and human communities Solution: responsible aquaculture

Issue: Water Pollution Problem: Some production systems allow uneaten food, fish waste and drugs and chemicals to pass into surrounding waters, where they can harm ecosystems and impair water quality Solution: Use closed recirculating systems Grow more than one species (mussels raised on ropes suspended in the ocean can help cleanse waters polluted by salmon raised in net pens. Minimize use of antibiotics and anti-parasite drugs

Issue: Depleting wild fish stocks Problem: Deplete food resources for wild cousins of farmed fish Farming predatory fish like salmon can use huge amounts of small, oily wild fish like anchovies, menhaden, mackerel and herring, leaving no food for wild fish ~1/3 of the current annual catch has been used for animal feed Solution: Farm vegetarian or semi-vegetarian fish such as tilapia and catfish or filter-feeders like mussels or clams Feed predatory fish a semi-vegetarian diet supplemented with fish byproducts

Issue: Invasive Species Problem: Escaped farmed fish can pose serious threats to wild fish populations by competing with them for food and habitat and transmitting disease and parasites Solution: Farm species native to the region to reduce the potential harm from introducing a new fish species. Use closed systems like tanks, rather than "leaky" net pens or cages, to prevent escapes. Mark fish and require public reporting of escapes, to identify culpable suppliers.

Issue: Endangering Sea Animals Problem: To keep them from feeding on captive fish, wildlife such as seals, sea lions and birds are often harassed with firecrackers or loud underwater speakers that can cause disorientation, pain or hearing loss. Solution: Site farms far from places where marine mammals live or hunt, or birds congregate.   Use tight nets to prevent access by predators to ponds, tanks, and net cages.