Replies to This Discussion

Permalink Reply by Kobus Jooste on May 2, 2011 at 10:26am

There is much to reply to, but just some starting points:

• Aquaculture as an industry is a pollutor, whether it is salmon or tilapia.  Salmon is actually worse because of the high protein feed they get.  Sustainable practices are available, but as to how far they will be adopted depends on legislation and the market - the better the farm, the more expensive the fish will become.  People cannot gripe about the type of feed, the environmental practices of the farm and still demand a cheap fish. 
• You are what you eat and you yield what you feed.  Tilapia can have a different body composition if it is fed less corn and soy, but as a bream, will never be the best source of Omega fatty acids.  Since when was it supposed to be though?  You can't get it all and if the fish is not a good source of Omega fatty acids, even if the food contains it (which will likely come from fish oil, which puts the whole idea in a bad feedback loop).
• On the invasive side, modern hybrids are available that give you a (nearly) all male offspring.  These are expensive, and again, using them will push up the price of the fish.  I would suggest that these hybrids become required by law in areas where the species can be invasive though. Alternatively the use of pen farms should be severely restricted in areas where the fish can become established.  Again, this practice will push up the end cost of the fish.

Permalink Reply by David Hart on May 2, 2011 at 10:26am

I just started raising purslane. It's very high in omega 3. I haven't tried feeding it to my tilapia yet. I don't think it will be an issue. They eat the bitter lettuce I toss them.

Folks with chickens might want to give it a try too.

 

http://en.wikipedia.org/wiki/Portulaca_oleracea

Purslane contains more omega-3 fatty acids (alpha-linolenic acid in particular^[4]) than any other leafy vegetable plant. Simopoulos states that Purslane has 0.01 mg/g of eicosapentaenoic acid (EPA). This is an extraordinary amount of EPA for land based vegetable sources. EPA is an Omega-3 fatty acid normally found mostly in fish, some algae and flax seeds.^[5] It also contains vitamins (mainly vitamin A, vitamin C, and some vitamin B and carotenoids), as well as dietary minerals, such as magnesium, calcium, potassium and iron. Also present are two types of betalain alkaloid pigments, the reddish betacyanins (visible in the coloration of the stems) and the yellow betaxanthins (noticeable in the flowers and in the slight yellowish cast of the leaves). Both of these pigment types are potent antioxidants and have been found to have antimutagenic properties in laboratory studies.^[6]

100 grams of fresh purslane leaves (about 1 cup) contain 300 to 400 mg of alpha-linolenic acid.^[7] One cup of cooked leaves contains 90 mg of calcium, 561 mg of potassium, and more than 2,000 IUs of vitamin A

Permalink Reply by TCLynx on May 3, 2011 at 6:24pm

LOL and in much of the world people see Purslane as a weed.  I've grown it myself as the cultivated varieties are better tasting than the wile stuff around here.

 

Yes agree with what Kobus says.

 

Also agree with Sylvia that recirculating aquaponics takes care of many of the issues while more research into altrenative feed substances as David suggests would be beneficial.