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Carbon chains with carboxyl groups but not amino groups are
called fatty acids. They are written as, for example, H3C-CH2-CH2-
CH2-COOH or more simply as H3C(CH2)nCOOH, where n is the number of
repeated units. Some have short chains and some have
long chains. Fishes can convert some kinds to other kinds. Fatty
acids with only single bonds are called saturated (for example, H3C-
CH2-CH2-CH2-COOH) because all their available chemical bonding sites
are saturated with hydrogen atoms. They are usually semi-solid and
are called fats.
Other fatty acids, mostly found in plants, have one or more
double bonds between adjacent carbon atoms (C=C). The double bond
is not saturated with hydrogen atoms. Unsaturated fatty acids are
usually liquid and called oils.
Unsaturated fatty acids that fish cannot make from precursors
are called essential fatty acids. Fatty acids can have short chains
(three carbons or so), or long chains of 16 to 24 carbons, and be
saturated (no double bonds) or unsaturated. Long chain fatty acids
with many double bonds are the highly unsaturated fatty acids or
How many carbons are in the chain and where are the double
bonds? The number and positions of double bonds are given latin and
greek names. The ending anoic refers to a saturated acid
and the ending enoic refers to an unsaturated acid.
Baby fish especially need the 18 and 20 carbon unsaturated
fatty acids called eicosapentaenoic (ESA) and dodecaenoic (DCA)
acids, often called the omega-3 and omega-6 HUFAs. These HUFAs can
make the difference between raising 5% or 75% of a spawn. Added to
brine shrimp nauplii or rotifers, the little critters fill their
guts, becoming little HUFA delivery packages. HUFA enriched live
foods produce better growth and survival. Natural substances rich
in HUFAs can be added to dry foods. The best sources are mysids,
edible shrimp, menhaden, anchovy, and cod, and almost any coldwater
marine fish or marine crustacean.
Robert J. Goldstein, Ph.D.
Robert J. Goldstein & Associates, Inc.
8480 Garvey Drive
Raleigh, NC 27616 USA
tel (919) 872-1174
fax (919) 872-9214
e-mail rgoldstein at rjgaCarolina_com