[Catalyst 2016] Final

Prevailing notions of the ocean make
it seem as if it is “too big to fail” since
it takes up 70% of the surface of Earth
and contains 321,003,271 cubic miles of
water. 1 Additionally, most of the oceans’
immense biodiversity has yet to be
documented. The Census of Marine Life
estimates that there could be between
178,000 to 10,000,000 different species
living in ocean shoreline habitats due to
the vast abundance of photosynthesizing
microbes. 2 However, like any ecosystem,
the oceans are not immune to
anthropogenic and environmental
stressors such as overfishing, climate
change, and pollution. There are many
interconnected problems surrounding the
way in which people currently treat the
oceans. Extracting large amounts of fish
for human consumption threatens the
dynamic balance that currently exists and
threatens scientists’ potential for making
groundbreaking discoveries about what
lies below.
In 2010, the United Nations predicted that
over 80% of the world’s fish are reported
as fully exploited or overexploited, and
thus “require effective and precautionary
management”. 3 Overexploitation refers to
the extraction of marine populations to
unsustainable levels. 4 Fishing techniques
have become exponentially more efficient
since the Industrial Revolution, focusing
on getting the largest catches in the
fewest trips. Today’s fishing fleets are so
large that it would require two to three
times Earth’s supply of fish to fill them. 4
These harmful practices lead to three
main types of overfishing: growth fishing,
recruitment fishing and ecosytem fishing.
1. GROWTH
THE REMOVAL OF LARGER FISH LEAVES
BEHIND ONLY INDIVIDUALS THAT ARE
TOO SMALL TO MAXIMIZE THE YIELD,
OR FULL AMOUNT OF FISH THAT
COULD THEORETICALLY BE OBTAINED. 5
Unfortunately, the most popularly
consumed fish species are subject
to all three practices. Bluefin tuna,
sturgeon, sea bass, and Atlantic
salmon are examples of large,
long-lived predatory species that
only provide a few offspring each
breeding cycle. 5 For example, Bluefin
tuna release ten million eggs each
year, but only a small number survive
to adulthood. Even then, these
tuna do not reach reproductive
maturity until eight to twelve years
of age. 6 When the largest fish are
specifically targeted, many ecological
consequences arise. Removing the
largest fish of the largest species in
an ecosystem significantly decreases
the mean size for that species. As
a result, only smaller fish are left
to reproduce. 7 This shift causes
trophic level decline: as species at
higher trophic levels are overfished,
fishermen decide to catch the
comparatively larger fish at lower
trophic levels. 7 This vicious cycle
continues so that the average size of
fish consumed decreases significantly.
This phenomenon, known as “eating
down the food chain,” puts many fish
at risk, including herbivorous fish in
coral reef ecosystems. 7 To maintain a
coral-dominated state, herbivorous fish
consume macro-algae that otherwise
would overgrow and suffocate corals.
When coral-dominated reefs become
overtaken by macro-algae, habitats
for many other fish and organisms are
severely reduced. Over 25% of the world’s
fish species live exclusively within these
three-dimensional coral communities,
2. RECRUITMENT
WHEN ADULT FISH ARE
EXCESSIVELY TAKEN OUT
OF THE ECOSYSTEM,
RECRUITMENT AND STOCK
PRODUCTIVITY DECREASES. 5
which themselves only take up 0.1% of
the ocean floor. 5 Not only are species
being depleted at the very top of the food
chain, smaller species that are endemic
to specific ocean environments are also
indirectly experiencing survival pressure.
These problems are further magnified
by the fact that current fishing practices
produce a large amount of by-catch,
or the incidental capture of non-target
species. 5 The rustic image of a humble
fisherman using a single hook at the
end of a line no longer reflects reality
for most commercial fishermen. Now,
longlines are weighted at the bottom
3. ECOSYSTEM
THE TARGETING OF A
PARTICULAR SPECIES LEADS
TO SERIOUS TROPHIC
CASCADES AND ECOLOGICAL
CONSEQUENCES. 5
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CATALYST