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Chapter 12: Food from the Oceans
Major Sources of Ocean Pollution
4 major types
1. Oil
2. Toxic Material
3. Dangerous Debris
4. Withdrawals and Deposits
Major Sources of Ocean Pollution…
1. OIL
• When it comes to mixing oil and water, oceans suffer
from far more than an occasional devastating spill.
•Disasters make headlines, but hundreds of millions of
gallons of oil quietly end up in the seas every year, mostly
from non-accidental sources
Major Sources of Ocean Pollution…
2. Toxic Material
• Industrial, agricultural, household cleaning, gardening,
and automotive products regularly end up in water.
• TBT, or tributyl tin, is added to boat paints to kill or repel
barnacles and other nuisance organisms that foul ships' hulls.
Major Sources of Ocean Pollution…
3. Dangerous Debris
• Our trash kills. When odds and ends of life on land-particularly plastics--end up in the sea, they pose hazards to
marine life..
• Animals drown or strangle from getting tangled in
discarded or lost fishing gear, or suffer and even die from
eating plastics and other garbage
What is the
relationship
between these
pictures?
Major Sources of Ocean Pollution…
4. Withdrawals and Deposits
• For thousands of years humans have viewed oceans as
vast dumps for domestic, municipal, and industrial garbage
• Enormous deep-sea resources will undoubtedly attract more
miners in the future, as easy-to-reach deposits on land are
depleted.
Example: Mining sand from the shores of
Belize for landfills in Central America
Impact of New Catch Technology on the Environment
Factory freezer Trawlers have likely had the most
significant and negative impact
• Highly efficient at catching fish which greatly reduces
the population & reproduction. Large diesel engines,
echo sounding equipment, onboard freezers, and GPS
navigation contribute to their efficiency.
• Destruction of the ocean floor by trawls/draggers
eliminates good spawning locations for fish.
Furthermore it disperses eggs making fertilization
more difficult.
• By catch is often discarded. Some
regulations require ships to return
with low levels of by catch.
• Traveling great distances and being able to stay at
sea for long periods allows trawlers from all over the
world to congregate in good fishing areas. This puts
added pressure on the fish stock.
Declining fish resource & the livelihood of fishers.
The declining fish resources may have a variety of
affects on fishers.
• Fishers may concentrate more on conservation.
Fishers and the community they live in will have to
diversify or die.
• Develop aqua-culture ex. Bay d’Espoir
• Golf course construction ex. Frenchman’s cove
• Sea weed aqua-culture ex. Isle aux Morts
• Eco-tourism ex. Northern Peninsula
• Fish underutilized species
Fishing Technology
Gear & technology = (figure 12.12 on page 206 shows all
fishing gear very well)
Fixed gear such as:
•gill nets,
•long lines
•purse seines
•Otter trawls
•Trolling lines
Fishing Gear is divided into 2 types:
1. Pelagic
2. Demersal
Pelagic means living in open oceans, fish include capelin,
cod and herring
Demersal mean to dwell at or near the bottom of a
body of water , fish species include flounder, halibut
and turbot
Demersal Fishing Gear
1. Otter Trawl
• is the most common method used to catch demersal species
• The funnel shaped net scoops the fish off the bottom.
However there is a lot of concern lately over the amount of
damage the trawl does as it scraps along the ocean floor
• Otter Trawl at
Marine Institute
Flume Tank
Otter Trawling
2. Gill Nets
•Can catch pelagic or demersal species.
•The thin mesh hangs in the water and fish get caught
up as they try to swim through it
• The term ghost nets usually refer to this type of net
that has gotten away from its mooring or been lost. It is
believed to continue catching fish for years as it drifts
though the ocean.
3. Longline:
• This is a more efficient way of doing the old fashion
baited hook
• It is commonly used to catch dermersal species but can
be used to catch pelagic species
• The difference is that many hooks are hung off a long
main line which floats on top of the water.
• This is one of the techniques that has very little
environmental opposition.
LONGLINES
4. Traps:
• Traps are specifically designed for certain pelagic species.
• They crawl in and can not crawl out. The lobster and
crab pots are good examples.
Pelagic Fishing Gear
1. Trolling:
• works well for pelagic species like salmon, tuna & bill fish.
• Fishing lines are dragged behind the boat which trolls
along at slow speed.
2. Purse Seines:
• These are particularly good for pelagic species.
• Two boats are required as one holds one end of the
net while the other circles the net around the school
of fish.
• The purse string closes the bottom of the net catching
the fish inside.
Sustainability in Fisheries…
• Sustainability refers to the ability to keep a
resource in existence or to maintain a resource for
the future.
There are several ways to make our fishing
resources sustainable for the future.
1.
2.
3.
4.
5.
Aquaculture and Fish Hatcheries
Habitat Preservation or Restoration
Quotas that can support the stocks
Using Gear that is less damaging to fish and fish habitat
Fishing of alternative and under-utilized species