David Suzuki Foundation: Oceans and Fishing
I must admit, the first time I had heard the phrase "fish farming" I pictured planting fish in the dirt and watching them grow. OK, so I was a small child at the time but nonetheless the term sounded funny. It still sounds funny to me even though there really is no reason why it should. We raise chickens, ducks, rabbits, pigs and cows (and other animals) on land for food, so why shouldn't we raise fish in the water for food? After all, seafood is an excellent source of protein used by many cultures throughout the world as well as an excellent source of the polyunsaturated fatty acid, omega-3 ("fish oil"), which has been shown to be beneficial to humans. Also consider that the ocean is huge, so there must be a huge amount of fish there for us to take advantage of, right?
If only it was this easy. Yes the oceans are very large, but like everything else, the oceans are finite in size and they certainly do not have an unlimited supply of fish. Unfortunately, the human appetite for seafood is growing as if the supply was unlimited. In 1960, the world's population was about three billion, roughly half of what it is today. But while the human population has doubled since then, the amount of seafood we consume on a yearly basis has increased by a factor of about 3.5. This is a remarkable feat considering that we tend to take the biggest and most reproductively mature fish we can find out of the ocean. As we take more mature fish, there are fewer left behind to reproduce, thus lowering the supply. Eventually, we could fish some species to extinction. One way to avoid some of the problems is to raise fish in "fish farms".
A fish farm works much as any land-based animal farm does; fish are kept in pens, fattened up and harvested. Sounds pretty simple and for the most part it is. If you eat seafood, you may have even had farm-raised fish and not even known it. Much of today's popular seafood is farm-raised; catfish, clams, oysters, sturgeon, trout and tilapia. Many species, such as tilapia, are raised in land-based freshwater recirculating tanks that have almost no impact on the environment; while others, such as oysters and clams are raised in intertidal pens and on beaches respectively, with some environmental impact. For example, because clams are farmed on beaches, farmers cover these areas with plastic netting to prevent migratory birds from eating young clams, thereby disrupting the birds' feeding patterns. As bad as this may seem, it doesn't even come close to the problems caused by farming salmon.
Salmon, unlike the species discussed above, are carnivorous. This means they need to be fed other fish. Because of this, raising salmon in farms actually represents a net loss of fish throughout the world. It's been estimated that between two and five kilograms of fish is required to grow one kilogram of salmon. It's also been estimated that 15 - 52 kilograms of waste per square meter of seabed accumulates beneath the salmon farm, most of which is fish excrement, dead fish and fish blood. The accumulated waste can lead to anoxic conditions (i.e. lowered oxygen levels) in the sediments below the farm and the waste is a huge source of nitrogen and phosphorus. The Suzuki Foundation puts it this way: "The average person excretes 4 kilograms of nitrogen and 1.1 kilogram of phosphorus per year. Typically, for every tonne of farmed salmon produced, 55 kilograms of nitrogen and 4.8 kilograms of phosphorus are excreted into the marine environment." Multiply that by the 900,000 metric tonnes of farmed salmon and that's a lot of waste; equivalent to the nitrogen waste of 12 million people and the phosphorus waste of 4 million people! This is just one problem associated with salmon farming. Others include chemical pollution, overuse of antibiotics, pesticides and fungicides, and escapes of farmed salmon into the wild. All of these add up to a huge environmental impact.
There is nothing wrong with aquaculture if done properly. In fact, due to increased fishing pressures on the ocean, it may become the only way to harvest fish sustainably. The time to clean up the mess is before there is one; that time is now. Bon appétit!
- Go to the Monterrey Bay Aquarium website and analyze your seafood diet. If you don't eat seafood, use the diet of someone you know. Is your seafood diet environmentally friendly? If not, what could you do to make it so?
- How does the amount of waste produced from a typical fish farm compare to that of a typical animal farm?
- We require human waste to be treated before it is discharged into the water. Should we require waste from fish farms and animal farms to be treated similarly? How much of an impact would a requirement such as this have on the producer's bottom line? Is there any way to accomplish this without having a huge impact?
- David Suzuki Foundation: Oceans and Fishinghttp://www.davidsuzuki.org/Oceans/Fish_Farming/default.asp
The David Suzuki Foundation works to find ways for society to live in balance with the natural world. There is lots of good information here on aquaculture, especially in the area of salmon farming.
- Grace Factory Farm Project: Fish Farminghttp://www.factoryfarm.org/fish.html
From the website: "GRACE is a not-for-profit corporation established in 1996. The GRACE Factory Farm Project was established to eliminate factory farming in favor of a sustainable, economically viable and environmentally sound agricultural sector".
- The Salmon Nationhttp://www.salmonnation.com
This website is dedicated to the "Salmon Nation", that area where salmon live and grow. It includes a lot of information about salmon, both farmed and wild.
- SectionZ #1: The Hidden Costs of Farmed Salmonhttp://www.sectionz.info/issue_1/
This is quite an eye-opening article. If you're a salmon lover, proceed with caution!
- Nutrition Matters: Fish - The Latest Technology in Thermometers or Tonight's Dinner?http://nutrition.tufts.edu/news/matters/2001-03-12.html
This article on the Tufts University School of Nutrition website talks about unsafe mercury levels in fish.
- PiscesTT: The European Forum for Aquaculture Education and Traininghttp://www.piscestt.com/pisces/default_en.asp
This is a very interesting site that has everything you want to know about aquaculture from a pro-aquaculture viewpoint.
- Monterrey Bay Aquarium Seafood Watchhttp://www.mbayaq.org/cr/seafoodwatch.asp
This is an excellent site with a ton of information. You can even check to see how environmentally friendly your seafood diet is.
- The British Columbia Salmon Farmers Associationhttp://www.salmonfarmers.org
This is a very interesting site. From the website: "The BC Salmon Farmers Association is the voice of the province's environmentally sustainable salmon farming industry. The association is a forum for communication, a vehicle for lobbying, and a point of contact for stakeholders and the public."
All material (except for some code and external links) © Jeffery A. Schneider, 2003