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Introduction
Important natural / living resources
Renewable natural resources
Important components of the
ecosystem
Distribution of fish
Freshwater fish
Marine fish
Lower course
of rivers &
lakes
Continental shelf
Distribution of fish
The global distribution of fish
Areas producing about
50% of commercial fish
harvest
Upwelling areas the main fishing zones
Average daily plankton
production
mg of carbon per m2
>500
250-500
100-250
<100
99% of the fish stock
concentrated within 200
nautical miles off the
coast which are
plankton rich
Reason accounting for the
distribution of fish
The main reason:
Fish feed on plankton (including unicellular
plants).
They associate with the plankton.
Plankton
Small fish
Large fish
Reasons accounting for the
distribution of plankton
Unicellular plants need: Condition in these
areas:
Carbon dioxide
Shallow water - light
Sunlight
can reach most part.
Nutrients
Close to continent receive loads which
are rich in nutrient.
Another important factor Temperature
Most of the ocean is cold.
Advantages of low temperature:
 solubility of oxygen in water
 metabolic rates  need less energy  need
less food.
Cold…!
Good!
Present situation of the world's
fisheries
• People get an average of 20% of the animal
protein in their food from fish and shellfish.
• Contribute 30 - 90% of animal protein in
Asian coastal and Island countries.
• 87% comes from the ocean and 13% from
fresh water.
Fisheries
• Concentration of particular aquatic
species suitable for commercial
harvesting in a given area of the ocean.
However, only a few groups harvested
extensively (40 out of 200000 known
species – half annual harvest which is
near to its maximum sustainable yield) cods,
herrings,
jacks,
redfishes,
mackerels and tunas. Why?
Tradition and taste
Operating costs in what aspects?
• More than 90% of the fish obtained by
small and large motorized fishing boats to
hunt and gather over a large area.
• 30 - 40 % of the operating costs spent on
fuel. --> higher price of many favourite
types of fish and shellfish.
Is the fish resources renewable?
• The highest rate at which a potentially
renewable resources can be used without
reducing its available supply.
• 1950 - 1970, the weight of fish catch grew
annually by 7% and increased more than
threefold. The rate of growth has slowed
down and the marine catch may soon reach
the estimated sustainable yield.
• Although the total fish catch has grown, the
world-wide per capita fish catch has
declined.
The human impacts to fish
Many human activities causes impact to fish:
Over-fishing
Illegal fishing practices
Water pollution
Over-fishing
World population 
Demand on fish 
Rate of removal of fish > rate of production of fish
Over-fishing
Over-fishing
Fishermen try to catch more fish by
using net with smaller holes.
Immature fish are also captured.
Less fish can spawn.
Foreign exchange for third world countries
Illegal fishing practices
Destructive fishing methods
Fish Bombing
(use of explosives)
Fish Poisoning
(use of toxic
substances)
Illegal fishing practices
Not only kills the target fish, but also
nearby small fish and even plankton.
The related food chains & marine
ecosystem are destroyed.
drift net fishing, dynamite / poisons destroy habitat, pollution, destruction of
mangroves, coral reefs and population
growth.
Disadvantages of drift net fishing on p. 4
Drift net fishing
• Indestructible nylon-mesh
• 15 meters deep and is up to 65
kilometres (40 miles) long
• Intend to catch squid, tuna, swordfish,
sea trout and salmon
Disadvantages of drift net fishing
• Not only depletes the target species but
also kills dolphins, turtles, seals, sharks
or even whales that entangled in the
fine mesh of the nets
•Ghost net entangled and kill fish,
marine mammals and birds year-round
for centuries.
Water pollution
Various types of water pollution:
Chemical pollution
Thermal pollution
Oil pollution
Acid rain
Chemical pollution - organic and
inorganic wastes
Through series
of decomposition
Nitrates
Aerobic bacteria
Sewage
Algal bloom
Chemical
fertilizer
Oxygen depletion
Death of aerobic organisms
Chemical pollution - toxic chemicals
Taken in by fish
Heavy metal
Form toxic
compound
DDT
Being accumulated
along the food
chain
DDT
Death of fish
Thermal pollution
Hot water discharged from power station:
 solubility of oxygen in water
 metabolic rate   the oxygen
consumption
Favours the growth of algae.
Oil pollution
Oil spillage causes the death of fish by:
Oil is toxic.
Oil cuts off the oxygen supply:
It prevents the oxygen from dissolving into the
water.
It prevents the entry of sunlight. Green plants
cannot carry out photosynthesis.
Acid rain
Exhaust gases from vehicles, factories,
incinerators & power stations contain acidic
gases.
They dissolve in rain water to form acid rain.
 acidity of water  death of fish and other
organisms.
Case studies on p. 3:
Peruvian anchovy catch
• Reasons for decline of Peruvian anchovy to
In 1953, Peru livestock feed 20% of
commercial extinct:
annual commercial
However,
between fish
1971catch.
and 1978, the
i.Peruvian
El Nino -anchovy
Southern became
Oscillation
kills
commercially
phytoplankton which are the major
extinct.
food for Peruvian anchovy.
ii. Government keep on financing fishing
industry in order to pay off the loans
and avoid people out of work.
Group discussion on any possible
solutions and the difficulties arised
• Report and give summary
Conservation
How to conserve?
Government
Individual
What government should do
Control the rate of removal rate of removal  rate of production
FISH HALTING in South China Sea
iv. Better management
1982 United Nations Convention on the Law of
the Sea by 159 countries.
This treaty gives all coastal countries the legal
right to control fishing by their own fishing
fleets and by foreign ships within 364 kilometers
(200 nautical miles) of their coasts.
If enforced, this treaty can reduce over-fishing.
However, 22 countries refused to sign or ratify the
treaty because
(1) Conflicts between countries and islands. They
disagreed the mineral and living resources in the
open ocean belonging to the entire world so as to
share their resources and profits with other
countries especially the LDC.
(2) Difficult to control.
What government should do
Promote fish
breeding
along
coastline & at
inland pond
Stop fish
bombing
&
poisoning
What government should do
Regulate the
discharge of
waste - treated
before discharge
Control the use
of fertilizer - no
excess amount
is used
What government should do
Educate people
about the
importance of
conservation of
fish
Use fuel of low
sulphur content minimize the
amount of
sulphur dioxide
produced
What individual should do
Control of fishing gear
Avoid the consumption of Humphead Wrasse
and Giant Grouper
Reduce the consumption of wild-caught live reef
food fish e.g. Leopard Coralgrouper
Avoid the consumption of sexually immature
species
i. Consume new species
Processing the new species to acceptable
taste.
ii. Aquaculture (e.g. Salmon in Norway)
Change to substitute such as cultured LRFF
and freshwater fish
.
High technologies required, to avoid destruction
of natural habitats and causes pollution.)