[OANNES Foro] Retention of fish for consumption by local populations could help to tackle human disease caused by nutrient deficiencies

[Mario Cabrejos]

Nature 574, 41-42 (2019)

doi: 10.1038/d41586-019-02810-2

 

Analysis of the nutrient composition of fish caught around the globe reveals
locations where the retention of fish for consumption by local populations
could help to tackle human disease caused by nutrient deficiencies. 

How the global fish market contributes to human micronutrient deficiencies

 <javascript:;> Daniel Pauly 

25 September 2019

https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&sa
p-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-cam
paign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-2019
0926-EAlert&utm_content=EN_internal_33925_20190926

Eating fish is good for us. Fish are a source of micronutrients that help to
prevent nutrient-deficiency diseases, which are a leading cause of infant
deaths worldwide. Determining whether the consumption of locally caught fish
could reduce the incidence of nutrient-deficiency diseases in countries
particularly affected by this problem requires having access to the relevant
data.  <https://www.nature.com/articles/s41586-019-1592-6> Writing in
Nature, Hicks et al.
<https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&s
ap-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-ca
mpaign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-201
90926-EAlert&utm_content=EN_internal_33925_20190926#ref-CR1> 1 report their
assessment of the nutritional content of 367 species of fish. For 43
countries, the authors mapped the relationship between the fish-derived
nutrients available from fisheries' catches and the prevalence of
nutrient-deficiency diseases in communities living within 100 kilometres of
the coast.

When assessing the nutritional composition of fish stocks, Hicks and
colleagues focused on six crucial micronutrients: calcium, iron, zinc,
selenium, omega-3 and vitamin A. They also considered protein content. Using
some previously available data, the authors generated a model that could
correctly predict the levels of these nutrients in different species of
fish. By mining databases containing information about fisheries' catches
taken between 2010 and 2014, the authors gathered information about the
amount and type of fish caught in each country's exclusive economic zone
(EEZ) - the area of its coastal waters over which it has sovereign fishing
rights. Hicks and colleagues used their model to estimate the nutrients
available from these fish catches and thus determine the spatial pattern of
this nutrient availability in global fish catches. For example, they noted
that tropical fish have higher concentrations of calcium, iron and zinc than
have fish from other regions.

In developing countries around the tropics, fish are not usually just
another healthy complement to an already rich assortment of foodstuffs.
Rather, for millions of people living in these regions, fish add the missing
micronutrients and proteins to what would otherwise be an unbalanced diet.
In many developing countries, fish are the food source
<https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&s
ap-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-ca
mpaign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-201
90926-EAlert&utm_content=EN_internal_33925_20190926#ref-CR2> 2 that provides
the majority of the inhabitants with most of the micronutrients studied by
the authors. The protein from fish boosts the nutritional content of typical
diets in such countries, where calories are obtained mainly from foods such
as maize (corn) or rice.

Hicks and colleagues' data demonstrate that fisheries' catches in some
developing countries should be enough to meet the key micronutrient needs of
their populations. For example, more than 75% of the population in Namibia
is at risk of calcium deficiency, even though enough fish is caught there to
remedy this situation. In some cases, ensuring that even a fraction of a
country's total fish catch is retained for local consumption could have a
substantial impact on public health. This is particularly true for children
under five years old, during a crucial stage of their development when
micronutrient deficiencies have a severe effect. For 22 of the countries
that Hicks and colleagues studied, 20% or less of the fish caught could
provide enough key micronutrients to meet the needs of all children under
five years old.

Not only do nutrient shortages harm public health, but this problem has a
knock-on effect of lowering gross domestic product. It might be supposed,
then, that the governments of developing countries in the tropics - along
with international development organizations or institutions such as the
United Nations - would be doing everything possible to encourage the
domestic consumption of fish caught in the EEZs of these countries. However,
most economic-development policies, including those of these countries
themselves, are geared towards promoting fish exports to match the
insatiable demand for fish in the markets of high-income Western countries
and East Asia
<https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&s
ap-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-ca
mpaign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-201
90926-EAlert&utm_content=EN_internal_33925_20190926#ref-CR3> 3.

The waters surrounding developed countries became overfished before
overfishing began to occur in other countries. For example
<https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&s
ap-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-ca
mpaign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-201
90926-EAlert&utm_content=EN_internal_33925_20190926#ref-CR4> 4, the combined
fisheries' catch in the North Atlantic peaked in 1975, and the world's catch
peaked in 1996. The catch limits placed on overfished regions has led such
regions on a quest to obtain their fish from other sources. These days, much
of the haul in many parts of the developing world is either caught by local
fishermen and exported, or taken by foreign fleets - which, by paying a
nominal fee to access the EEZs of developing countries, catch fish for their
own markets. Such actions contribute to the scarcity of nutrients in many
developing countries.

This problem is perhaps greatest for countries on the northwestern coast of
Africa. There, fishing by fleets from the European Union, Russia and East
Asia - and high fish exports to the EU - have led to local fish scarcity and
price increases that have made fish increasingly inaccessible to local
consumers
<https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&s
ap-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-ca
mpaign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-201
90926-EAlert&utm_content=EN_internal_33925_20190926#ref-CR5> 5. In Senegal
in western Africa, one of the countries studied by Hicks and colleagues, a
small micronutrient-rich, herring-like fish called sardinella has been a
staple for centuries. A 2016 documentary film called An Ocean Mystery: The
Missing Catch (see  <http://go.nature.com/2kyjv51> go.nature.com/2kyjv51)
shows sardinella being smoked, dried and hand-processed by Senegalese women
and then trucked to the interior of the country, where these fish are the
only affordable main source of micronutrients and animal protein. The leader
of these workers emphasized in an interview in the documentary that it would
be a catastrophe if the sardinella supply was interrupted, because they
would have no fish to process.

Since then, this feared catastrophe has begun to happen. Despite much local
consternation, more than 40 industrial fish-processing plants have been
built, mainly by Chinese enterprises, along the coast of Senegal (see
<http://go.nature.com/2kva8bu> go.nature.com/2kva8bu) and neighbouring
countries (see  <http://go.nature.com/2jtmcjq> go.nature.com/2jtmcjq). These
plants process sardinella (Fig. 1) and similar small fish into an
animal-feed product called fishmeal. Many of the local fisheries, which had
traditionally supplied the regional markets with sardinella for human
consumption, now instead supply the fishmeal plants. These factories export
their product mainly to China, which is the world's largest fishmeal
importer, and it is commonly used there to feed farmed fish.



Figure 1 | Sardinella fish being processed in Mauritania to generate
fishmeal. In many developing tropical countries, a substantial proportion of
local fish catches are either exported for human consumption or processed
locally to generate fishmeal that is then exported and used, for example, to
feed farmed fish. Hicks and colleagues' analysis
<https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&s
ap-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-ca
mpaign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-201
90926-EAlert&utm_content=EN_internal_33925_20190926#ref-CR1> 1 suggests that
the retention of fish for local consumption could help tackle human disease
associated with nutrient deficiencies in countries where such conditions are
prevalent.Credit: Sylvain Cherkaoui/Reuters

Thoughtful consumers often insist that they eat fish certified as
sustainably caught. This nebulous term often implies a hope that such fish
suffered as little as possible, and that their stocks are somehow being
managed to ensure the continuation of an abundant supply. If such fish come
from fish farms, as is the case for most salmon on offer, this, too, is
considered a good thing, because it is widely thought that fish farming
relieves pressure on capture fisheries. However, using sardinella to make
fishmeal for farmed fish does not reduce the pressure on wild fish.
Moreover, it deprives people in the developing world on low incomes of
previously affordable, nutritious local fish - to aid the production of
costly farmed fish that is mainly consumed in high-income countries
<https://www.nature.com/articles/d41586-019-02810-2?WT.ec_id=NATURE-201909&s
ap-outbound-id=65009000AFAE4CFBDC842073DE65D49CD7308762&utm_source=hybris-ca
mpaign&utm_medium=email&utm_campaign=000_SKN6563_0000015362_41586-Nature-201
90926-EAlert&utm_content=EN_internal_33925_20190926#ref-CR2> 2.

When considering what fish we should eat, given that fish is good for us, it
is time to take a broader perspective about how "us" is being defined. Hicks
and colleagues' work points a way forward. The information they have
provided could be used to put a spotlight on fish availability when thinking
of ways to prevent human disease caused by micronutrient deficiencies.

References

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