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Tuna alert!
We have all been told that eating fish
is good for us. Tuna has been a longtime favourite, and represents
about 20% of the fish eaten in the United-States.(1)
It is an excellent source of protein, rich in omega-3 fatty
acid and low in calories. And because it is mostly sold ready-to-eat
out of the can, it is a practical food item for today's fast-paced
society.
But eating tuna does have a downside,
which we are often not well enough informed of; the level
of mercury in some species of tuna is increasing constantly,
while the numbers of bluefin tuna are plummeting in all oceans
of the world. The health risk from mercury is quite real,
as is the disappearance of some tuna species.
| Protect yourself
and help a threatened species |
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| tuna |
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Tuna
is a pelagic fish (i.e., which lives in the high
seas) and migrates widely through the oceans of
the world. The 5 main commercially fished tuna species
are; bluefin, albacore, bigeye, yellowfin, and skipjack.
They are related to sardines, herring and mackerel
(scombridae family). |
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| Adult bluefin |
| Photo: P.
Manzoni |
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Because
of its size, tuna is an apex predator with few natural
enemies. Bluefin tuna, the largest species, can
weigh up to 700 kg and measure 4 meters. However,
fishing bluefin tuna is extremely lucrative, and
one of these giants was sold for $180 000 USD
in Tokyo. It is the most endangered tuna species,
and the collapse of the bluefin tuna stocks seems
inevitable. This is because the bluefin tuna can
live more than 20 years and only reaches maturity
after many years (when it reaches 150 kg/230 lbs).
Overfishing has reduced its numbers to 10% of what
they were in 1970,(2)
and a large proportion of fish now being caught
is made up of juveniles which have not yet had time
to reproduce. The breeding population is not large
enough to ensure the survival of the species. |
|
Raising
bluefin tuna in pens (aquaculture) is not a solution,
since the young tuna are caught as wild stock and
harvested before they can breed. |
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| mercury |
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Mercury
is a neurotoxin - this means it can cause damage
to the brain and central nervous system. It also
affects the kidneys and lungs. Methylmercury, one
of the most toxic forms of mercury, is known to
affect learning ability and neuro-development in
children.(3)
Mercury gets into the environment by air (industrial
air pollutants, coal burning, incineration of garbage)
and by land or water (accidental or intentional
industrial spillage, garbage leachate in landfills).
The dispersal of mercury knows no boundaries. For
example, mercury released in the environment in
Asia can find its way into the Atlantic Ocean. |
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Prenatal
exposure to organic mercury, even at levels that
do not appear to affect the mother, may depress
the development of the central nervous system and
may cause psychomotor retardation for affected children.
Mild neurological and developmental delays may occur
in infants ingesting methylmercury in breast milk.
Affected children may exhibit reduced coordination
and growth, lower intelligence, poor hearing and
verbal development, cerebral palsy and behavioural
problems.(4)
Therefore, women of child-bearing age or who are
breast-feeding should be particularly concerned
by the consumption advisory below. |
|
Tuna, because
they are an apex predator (at the top of the food
chain) and are long-lived, can accumulate more mercury
than other fish (this is called bioconcentration).
This is also the case with swordfish, shark, flounder,
and other large fish. |
|
The State of California
filed a lawsuit against American canned tuna producers
for failing to warn consumers about exposure to
mercury in conformity with Proposition 65, a law
which requires that anyone at reasonable risk of
exposure be informed when substances classified
as toxins are present.(5) |
|
|
| consumption
advisory |
|
The
table below was prepared from information found
at www.OceansAlive.org (6) |
| How
many meals of this species can I safely
eat per month? |
abundance
and bycatch |
species |
woman |
man |
child |
small
child |
usual presentation |
| (5-11 years) |
(1-4 years) |
| bluefin |
0/month |
1/month |
0/month |
0/month |
fresh, sushi, sashimi,
restaurants |
threatened species,
high bycatch rate |
| albacore |
3/month |
3/month |
2/month |
1/month |
canned, sushi |
species in decline,
high bycatch rate |
| bigeye |
3/month |
3/month |
2/month |
1/month |
fresh, sushi, sashimi,
restaurants |
species in decline,
high bycatch rate |
| yellowfin |
3/month |
3/month |
2/month |
1/month |
canned |
species in decline,
high bycatch rate |
| skipjack
(listao) |
1/week
or more |
1/week
or more |
1/week
or more |
1/week
or more |
fresh, canned |
abundant species,
high bycatch rate |
|
|
| Note
- These recommendations are cumulative. For example,
if you eat 1 serving of bluefin tuna, you should
not eat any albacore tuna for the following month. |
| Bycatch
- Several fishing techniques catch important quantities
of other non-target species, such as marine mammals
(dolphins), turtles, other fish, and birds. These
animals die and are thrown back to the sea by fishing
vessels. |
| Advice
- If you eat canned tuna, buy light tuna rather
than white tuna. Analyses have shown that white
tuna contains 7 to 8 times more mercury than light
tuna.(7) Light
tuna is made with different species than white tuna,
namely yellowfin and skipjack (listao). Light tuna
is less expensive than white tuna, but it contains
less omega-3 fatty acids. |
|
| a
few good fish |
|
| Eat
small fish, such as mackerel, herring, and sardines,
all of which are abundant species. They contain
the same essential fatty acids as tuna, without
the problem of bioconcentration of mercury and other
contaminants. Below is a chart, prepared from information
published by the United States Department of Agriculture
(USDA): |
cross
reference chart of fish high in omega-3
fatty acids (per 100 g) |
| species |
calories |
fat |
protein |
omega-3 |
cholesterol |
sodium |
| bluefin
tuna |
144 |
4.9
g |
23.3
g |
1.17
g |
38
mg |
39
mg |
| yellowfin
tuna |
108 |
0.95
g |
23.3
g |
0.23
g |
45
mg |
37
mg |
| Atlantic
mackerel |
205 |
13.8
g |
18.6
g |
2.45
g |
70
mg |
90
mg |
| Atlantic
herring |
158 |
9.04
g |
17.9
g |
1.67
g |
60
mg |
90
mg |
| sardine |
178 |
11.9
g |
16.3
g |
1.87
g |
61
mg |
414
mg |
| wild
salmon* |
146 |
5.92
g |
21.6
g |
1.24
g |
45
mg |
46
mg |
|
|
| *
Warning - Do not eat Atlantic
Salmon, which is raised in pens for the
most part (aquaculture). It contains high levels
of dioxin, pesticides and PCBs because of the commercial
feed they are given. Furthermore, the high density
of fish in the pens requires the use of antibiotics.
Finally, salmon aquaculture is very damaging to
the environment because of the diseases the farmed
salmon carry which contaminate the wild salmon and
the pollution generated under and around the pens. |
| Note
- If you eat mackerel, be sure to buy Atlantic mackerel,
not Spanish mackerel or King mackerel. The latter
two species are much larger than the Atlantic mackerel
and contain high levels of mercury. |
|
| other
sources of omega-3 |
|
| Omega-3
fatty acids are also present in large concentrations
in some grains and nuts. Below is a chart of other
food sources readily available at health food stores:
|
omega-3
fatty acids in grains and nuts, as
alpha-linolenic acid (per 100 g) |
| source |
oil
form |
seed
or nut |
remarks |
| lin/flax
seed |
50
g |
20
g |
If you buy lin
seed (aka flax seed), be sure to grind
the seed (a coffee grinder works fine),
or put 2 table spoons in your blender
with milk, fruit juice and a banana.
Otherwise, the seed will pass through
you undigested. |
| pumpkin
seed |
15
g |
8
g |
Buy hulled pumpkin
seed (it is green in colour). Its natural
smoky taste make it a real treat you
will quickly crave. Roast some in a
pan with oil for a few seconds and add
then to your rice. |
| walnut |
11
g |
5
g |
Spruce up your
salads with small walnut pieces. |
| commercial
hemp seed |
20
g |
9
g |
Commercial hemp
contains less than 1% of THC, the active
ingredient in marijuana (a negligible
quantity). Cultivation and consumption
of commercial hemp is perfectly legal
in Canada. Furthermore, the hulled seed
contains no THC and is very rich in
protein (30%). Finally, commercial hemp
cultivation requires no pesticides. |
| soy
and canola oil |
7
g |
-- |
Use them for your
salad dressings rather than for frying,
as heat may reduce their health benefits. |
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Protocol |
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visit our campaign
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