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Bottom Trawling and Other
Destructive Fishing TechniquesMelissa and Jessica
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Bottom Trawling
Bottom trawls are a type of mobile fishing gear consisting
ofvery large nets that are dragged on the seafloor to benthic
organisms living on or close to the seafloor.
Two types of bottom trawling: Benthic and Demersal
Benthic is towing a net at the very bottom of the ocean
Demersal is towing a net just above the benthic zone
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Bottom Trawling
Bottom trawling has been used for over a century
The attachment of large, heavy roller and rockhopper gear
tobottom trawl nets, in combination with more powerful fishingboats
and other technical innovations, now allow access tovirtually all
of the continental shelves and deeper continentalslopes, including
areas with structurally complex habitat.
There is heavy fishing in the North Sea and the Grand Banks
It has a negative impact on coral Lophelia pertusa that is
hometo a wide range of deep sea creatures.
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Resuspension
Bottom trawling stirs up sediment
Suspended particle clouds can drift with the current for tens
ofkilometers
These particles introduce a turbidity which decreases light
levels atthe bottom and can affect kelp production and growth of
otherorganisms
Phosphorus is often found in high concentrations in sift
sediments,therefore resuspending nutrients solids like these can
introduceoxygen demand into the water column and cause oxygen
deficientdead zones.
Reintroducing sediment into the water column can also
createharmful algal blooms.
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The Before and After
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More Destruction
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Dynamite Fishing
Dynamite fishing is the use of explosives to stun and
killfish.
This illegal practice destroys the underlying fragile
habitat.
It is more commonly associated with tropical regions.
Commercial dynamite or homemade bombs are used. These
sometimes explode without warning and kill or injure
surrounding people.
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Dynamite Fishing
The underwater shock waves from the explosion stun the
fish and rupture their swim bladders. Some of the fish floatto
the surface but most sink to the ocean floor.
This technique not only kill fish, but also other marine
organisms in the area, and coral reefs.
There is no natural recovery of reefs.
The reefs can recover in 5-10 years from a single blast,
while
wide spread blasting causes continuous unstable rubble.
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Dynamite Fishing
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References
http://www.mcbi.org/what/wha
t_pdfs/Trawl_Impacts_%20on_C
orals.pdf
http://www.fishingnj.org/jpegs/
smaltrwlsml.jpg
