1. Effects of the El Niño Weather System on Fish Populations Off the Peruvian Coast
Tyler Franzen
November 22nd 2015

2. Introduction
Every two to seven years our planet goes through changes in its weather system known as
El Niño. An El Niño weather event is known to have a “bubble” of warm ocean water that
develops in the central and east–central equatorial Pacific right off the coast of South America
(Laws, 2000). El Niño is part of the El Nino Southern Oscillation or ENSO for short (Evers 2011).
ENSO is a cycle of warm and cold sea surface temperatures or SST of the central and eastern
Pacific Ocean (McPhaden, 2001). El Niño is caused by high air pressure in the western Pacific and
low air pressure in the eastern Pacific
(Laws, 2000). When the ENSO is not in
an El Niño phase (warm phase) it is in a
La Niña phase (cool phase) with sea
surface temperatures in the Eastern
Pacific below average and air pressures
are higher in the eastern Pacific and
lower in the western Pacific (Evers,
2011). In most years, winds from the
southeast push warm surface water
away from the coast known as upwelling (Evers, 2011). Upwelling brings cold-water rich
nutrients to the surface (McPhaden, 2001). Every so often (two to seven years) the pattern of air
circulation of the equatorial Pacific changes in a way that alters the normal oceanic upwelling.
During these years warm water is being pushed towards the surface instead of the usual nutrient
rich cold water (McPhaden, 2001). During El Nino, the upwelling brings up warm water with very
few nutrients, which results in devastating economic consequences to fishing industries off the
Figure 1: This graph shows the ENSO cold and warm SST
phases The University of Washington recorded from 1950 to
the year 2000. (McPhaden, 2001)

3. coast of Peru and Chili, this is especially true in the Anchovy fisheries (Salmon, 2015). Large
populations of fish and sea birds fall victim of El Niño and vanish while this weather system is
present. If Peru does not constantly regulate fishing, especially during El Niño years, there may
not be enough fish to repopulate in the years following. Currently Peru puts restrictions on the
length (in weeks) of the two fishing seasons as well as the tonnage of fish caught per Fishery and
the total for the season.
Cascade effect
El Niño affects manyof the countries bordering the Pacific Ocean, and a large portion of
these countries depend heavily on fishing every year. Fishermen in the area noticed that the ENSO
weather pattern many years ago
and coined the term "El Niño"
which is a reference to the Christ
child because periodic warming in
the Pacific near South America is
often noticed around Christmas.
"La Niña", chosen as the 'opposite'
of El Niño, simply translates to
"The Girl"(Salmon, 2015).
Plankton is the typical food source
for many fish including Peru’s primary catch, the anchovy (Laws, 2000). Fishermen, and later
scientists, have attributed poor fishing years due to the absence of plankton (Salmon, 2015).
Figure 2: Annual catch of Peruvian anchovies from 1950 to the year 2000.
Note that years with low yield correspond to years that had an El Niño
event. (Hannesson, 2001)

4. When there is a warm water upwelling off the South American Pacific Coast the plankton do not
have an adequate amount of nutrients from the warm water to thrive, thus is also affecting all
species that are higher up in the food chain (Salmon, 2015).
Prevention or Economic Devastation
Fishing is the second largest industry in Peru behind mineral and oil extraction (Gaulter,
2015). With that being said, any change in the annual fishing rates will alter the countries
economic portfolio immensely. When there are years without large amounts of fish caught, the
country struggles economically (Gaulter, 2015). If you did a side-by-side comparison of figure one
and two you would see a strong correlation between annual catch of Peruvian fish and sea surface
temperatures (SST) (Laws, 2000). Years with a high SST will have lower catch rates and vice versa
(Laws, 2000). In 1972 to 1973 there was a strong El Niño event that left fish populations critically
low for quite a few years into the future (Salmon, 2015). Some scientists are concerned that
overfishing during El Niño weather systems along with large fish and seabirds also feeding on the
smaller fish like the anchovy that recover after such an episode would be very long and difficult if
not impossible (Laws, 2000). Thankfully, after the 1972 episode the Peruvian government
enacted many laws in regards to fishing especially in years undergoing an El Niño episode (Laws,
2000). These laws have successfully prevented several fish wipeout events from taking place in
Peruvian territorial waters such as the El Niño episode in 1988-1989 (Laws, 2000). Even with
preventative measure in place, wipeout events may still take occur, thus the Peruvian government
must remain wary and proactive (Gaulter, 2015)

5. Conclusion
El Niño has global impacts not only with fishing but also weather patterns such as rain and
snowfall, humidity, and even air temperatures due to changes in jet streams. Today we can
predict with much certainty when El Niño events will occur. This helps fisheries and governments
prepare for these events so economies don’t collapse and crops, that do better during El Niño
weather conditions, can be planted during those seasons (Gaulter 2015). If governments do not
regulate fisheries properly, overfishing can quickly lead to years and years of low fish counts after
such an episode. Illegal fishing has become a major problem in South America but local
governments are increasing ocean patrols to combat such activities. Overall, laws and regulations
have become much more suited to these El Niño events over the past thirty years and thus have
kept overfishing in check. This allows the fisheries to go about as usual much sooner after an El
Niño episode than if these laws were not in place and properly enforced. The Peruvian
government does a good job of combating the ill effects of these ENSO events but there’s only so
much it can do given that we cannot control plankton populations during warm water phases.
Countries can only control the length of the fishing season and caps on how many fish can be
caught during these seasons. Overall, ENSO events have global impacts, but the real effects are
seen in countries such as Peru, where fishing is a major part of their economic portfolio and even
slight changes can largely affect the nations GDP.

6. Bibliography
Evers, J. (Ed.). (2011, March 11). El Niño - El Niño-Southern Oscillation (ENSO). Retrieved
November 19, 2015, from http://education.nationalgeographic.org/encyclopedia/el-nino/
Gaulter, S. (2015, July 26). El Nino's effect on Peru. Retrieved November 19, 2015, from
http://www.gulf-times.com/environment/231/details/448730/el-nino’s-effect-on-peru
Hannesson, R. (2001, November 1). A Note On Unsustainable Fisheries And Trends In World Fish
Catches. Retrieved November 19, 2015, from
http://www.fao.org/docrep/005/y3684e/y3684e05.htm
Laws, E. (2000). El Niño and the Peruvian Anchovy Fishery. Retrieved November 20, 2015, from
http://www.ucar.edu/communications/gcip/m12anchovy/m12html.html
McPhaden, M., & Soreide, N. (2001). NOAA/PMEL/TAO Frequently asked Questions about El Nino
and La Nina. Retrieved November 19, 2015, from
http://www.pmel.noaa.gov/tao/elnino/nino-home.html
Salmon, P. (2015, May 11). ENSO and the anchovy. Retrieved November 19, 2015, from
http://judithcurry.com/2015/05/11/enso-and-the-anchovy/