At 15:28 +1000 29/1/03, Phosphor wrote:

>> As far as I understand it, the fish are fed an artificial diet, >usually
>grain pellets. This is similar to what is done in >conventional farming of
>animals with similar results: >Unfavorable fat profiles and ratios.
>
>so farmed fish is bad because they are fed grains..
>
>>"These fish farms contribute to the problem because the >captive salmon
>must be fed. Salmon are carnivores and, unlike >vegetarian catfish that are
>fed grain on farms, they need to eat >fish to bulk up fast and remain
>healthy.
>
>and they are also bad because they accumulate PCBs from a heavy diet of
>small fish [ie from not eating grains].
>
>so do they eat grains or anchovies?
>which company are we talking about?
>which region are we talking about?

Hi Andrew,

You seem to be merging several posts here, and I fear you have wound
up a little confused. I certainly got a bit muddled trying to follow
your argument (not that you'd be surprised at that, I'm sure :)

The scope of the original discussion was 'farmed fish' in general.
It has subsequently narrowed to to 'farmed salmon'.

You have taken a couple of statements from the original discussion
and applied them to the salmon discussion, where they may not be
wholly appropriate.

So, let's split this back into two discussions.

Firstly farmed catfish, a vegetarian in its natural state, I believe.
Version SR12 of the USDA database shows that wild catfish contains a
n-6:n-3 fat ratio of 1:2. Farmed catfish contains a ratio of about 2:1.
Still a "good" source of n-3 fats, but nowhere near as good as the
paleo version of the fish.

I found a page which discusses the "least-cost formulation for
production feed for catfish". Wow, no big surprise that they are aiming
for the "least-cost": http://msucares.com/pubs/infosheets/is1463.htm

This page indicates that a "practical catfish feed formulation" is over
90% derived from wheat, soy, corn and rice. Since all those grains
contain lots of n-6 fats and only traces of n-3, it's hardly surprising
that farmed catfish have an unnatural fatty acid profile.


And secondly for farmed Atlantic Salmon.

Personally, I'm mostly interested in the Tasmanian ones, because
that's what I buy when I shop for salmon. This document dates from
Oct 2000, and is from an educational institution rather than an
industry source, but nevertheless:
http://www.utas.edu.au/docs/aquaculture/salmon/feeds.html

It says Tasmanian salmon get fed:

"fish meal, fish oil, grain products, milk products, binders and
vitamin/mineral premixes. Pigments such astaxanthin are incorporated
into the feeds to colour the flesh ... Attractants and feeding
stimulants, which are based on compounds such as amino acids,
also may be used to improve feed consumption and growth, and
to reduce waste"


Here's page with better data, but hard to read. Also probably more
relevant to Northern Hemisphere farming.
http://zoom.nap.edu/nap-cgi/rezoom.cgi?isbn=0309048915&page=53

It says "this diet has been used successfully on Atlantic Salmon...".
The diet consists of:
30% Herring
13% Soybean meal
17% Corn Gluten meal
16.5% Wheat middlings
10% Dried whey
11.5% Marine fish oil
1% Vitamins
1% minerals.

By my reckoning that's 58.5% of the diet from non-marine sources.
And 46.5% definitely from grains. I wonder how a paleo salmon
would gain access to grains and whey?

I would also expect the pellet manufacturers to be trying to
improve (i.e. reduce cost) on that recipe by replacing the expensive
Herring and Marine Fish Oil with cheaper alternatives. Perhaps beef
and poultry by-products would be included and make up perhaps 10% of
the overall mix. But apparently salmon are finicky eaters, so perhaps
they simply refuse to eat anything *too* inappropriate.

The USDA database (version SR12) shows wild salmon with n-6:n-3
of 1:4. Better source of n-3 fats than catfish, as expected. Farmed
salmon shows a ratio of 3:4. That's still an excellent source of n-3
fats, but only a third as good as wild salmon.


Some other interesting snippets I picked up along the way:

Farmed salmon in the Northern Hemisphere are routinely exposed
to a variety of insecticides to treat sea lice - including a couple
of organophosphates. http://logos.uba.uva.nl/ctz/vol69/nr01/a12

Heh, the "buyer's guide" at Aquafeed makes interesting reading:
http://www.aquafeed.com/search.php?site=bg&catid=1&posting=yes
This is the nasty stuff vendors are selling to fish pellet
manufacturers (and I wonder how much of the soy is GM?):
Soy lecithin, soy oil, soy protein concentrates and soybean meal.
Feather Meal, Poultry Meal, Poultry Fat, Poultry Blood Meal
wheat germ meal, wheat germ oil, scallop liver meal,
squid liver meal, wheat gluten, Oils, soya products,
peas, Soy protein concentrate, soybean meal, soy oil
oils, molasses, proteins, soybeanmeal, yellowcorn, feedwheat
Pellet binders, antioxidants, forage products and mold inhibitors.
Pellet binders, lubricants and water repellent binders.
Yucca schidigera feed additive, Herbal Feed Supplements
Pellet binder, Vitamins, Medicines, Probiotics

To be fair, the "good" stuff which probably makes up between 10 and
50% of the fish pellet is:
All types of krill, dried, frozen, liquid, meal and flaked
spirulina and chlorella algae powder shrimp, fish,
frozen artemia biomass, rotifers. Menhaden fish meal, oil
Penaeus monodon, Macrobrachium rosenbergii and fin fishes.
Fishmeal and fish oil from Peru.

 ...R.