Page 461 - Environment: The Science Behind the Stories

FaQ I love seafood, so how can I make TAble 16.1 Seafood choices for consumers 2
sustainable choices?
SUSTAINABlE ChOICES
SEAFOOd TO AvOId
1
To most of us, marine fishing practices may seem a distant phe- Catfish (U.S.-farmed)
nomenon over which we have no control, especially as more Clams (farmed) Caviar (sturgeon, imported, wild)
than 80% of seafood sold in the United States is imported. But Dungeness crab Chilean seabass/toothfish*
although we don’t have control over the seafood presented to
us, we have full control over which items we buy. Finding out Pacific halibut Atlantic halibut, flounders, soles
how seafood items were caught is difficult because this infor- Mussels (farmed) Mahimahi/dolphinfish
mation is not readily available to consumers in most cases. (imported, longline caught)
Thus, several organizations have devised concise guides and Oysters (farmed) Orange roughy*
smartphone apps to help consumers differentiate fish and Salmon (wild-caught, Alaska) Salmon (farmed or Atlantic)*
shellfish that are overfished or whose capture is ecologically Bay scallops (farmed) Blacktip Shark
damaging from those that are harvested more sustainably. For Shrimp (U.S.-farmed) Shrimp (imported)
instance, the Environmental Defense Fund provides a guide Tilapia (U.S.-farmed) Tilapia (farmed in Asia)
for sustainable seafood options, and TAble 16.1 includes a few
examples from its recommendations. Rainbow trout (farmed) Swordfish (imported)*
Yellowfin Atlantic tuna (troll/ Bluefin tuna*
pole-caught)
1 Fish or shellfish from healthy, well managed populations that are
nets and lines—expending increasing effort just to catch the caught or farmed in environmentally sustainable ways.
same number of fish. For example, a 2010 study showed that 2 Fish or shellfish from wild sources that are overfished, have high
British trawlers were working 17 times harder just to catch bycatch, cause extensive habitat damage or are farmed in ways that
the same number of cod and other fish as 120 years ago. harm other marine life or the environment.
More powerful technology also helps explain large * Limit consumption because of concerns about mercury or other
catches despite declining stocks. Today’s Japanese, European, contaminants.
Canadian, and U.S. fleets can reach almost any spot on the Adapted from: Environmental Defense Fund, March 2013. Safe sea-
globe with vessels that attain speeds of 80 kph (50 mph). food and responsible fisheries. http://www.edf.org.
They boast an array of military technologies developed for
locating enemy submarines, including advanced sonar map-
ping equipment, satellite navigation, and thermal sensing Some of these species were undesirable species that fish-
systems. Some fleets rely on airplanes to find schools of ermen formerly threw back when fishing for more marketable
commercially valuable fish such as bluefin tuna. Technology species, but underwent “image makeovers” to aid their sale to
cannot continue indefinitely to increase catches, however, as consumers. For example, the species of fish now called “orange
at some point there are simply not enough fish remaining to roughy” was called “slimehead” by fishermen because of its
be harvested, regardless of the technology used to find them. unique mucus canals. Similarly, the toad-colored “toothfish”
that fishermen once threw overboard has found new life as
Chilean Sea Bass, even though the species is not biologically
We are “fishing down the food chain” classified as a sea bass.

Numbers of fish do not tell the whole story of fisheries deple-
tion. Analyses of fisheries data reveal, in case after case, that as Marine biodiversity loss erodes
fishing increases, the size and age of fish caught decline. This ecosystem services
is not only because fishers prefer to take large fish, but also
because under intense fishing pressure, few fish escape being Overfishing, pollution, habitat change, and other factors that
caught for very many years, so that few have a chance to grow deplete biodiversity can threaten the ecosystem services we
to large size. Cod caught in the Northwest Atlantic today are on derive from the oceans. In the 2006 study that predicted global
average much smaller than those caught decades ago. It is now fisheries collapse by 2048 (p. 456), the study’s authors ana-
rare to find a cod over 10 years of age, even though cod of this lyzed all existing scientific literature to summarize the effects
age formerly were common. Because large female fish produce of biodiversity loss on ecosystem function and ecosystem ser-
far more young than small ones, the intense harvesting of larger vices. They found that across 32 different controlled experi-
fish makes it harder for populations to recover once depleted. ments conducted by various researchers, systems with reduced
In addition, as particular species become too rare to fish species diversity or genetic diversity showed less primary and
profitably, fleets begin targeting other species that are more secondary production and were less able to withstand distur-
abundant. Generally this means shifting from large, desirable bance.
species to smaller, less desirable ones. Time and again, fleets The team also found that when biodiversity was reduced,
have depleted popular food fish (such as cod) and shifted to so were habitats that serve as nurseries for fish and shellfish.
species of lower value (such as capelin, a smaller fish eaten Moreover, biodiversity loss was correlated with reduced filter-
by cod). Because this often entails catching species at lower ing and detoxification (as from wetland vegetation and oyster
trophic levels, this phenomenon has been termed “fishing down beds). This can lead to harmful algal blooms, dead zones, fish
460 the food chain.” kills, and beach closures.

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