Transcript The principles and values of artificial reefs and its applications in

The principles and values of artificial reefs
and its applications in Hong Kong
Yu Wing Yan 6B(31)
• Any man-made object placed in the sea as a habitat for marine
organisms
• Effective devices for attracting and supporting large populations of
fish
• Can enhance fishery resources
How do artificial reefs enhance fishery production?
• increase surface area
• providing substrate
• changing ocean current
• providing additional food source
• providing shelter
Increase surface area
Solid reef structure and hollow structure both occupy the same unit
of the sea floor
The taller and more complicated a structure, the more surface area
is available
Providing firm and stable substrate
Seabed with sand is constantly shifting
 Artificial reefs can provide a firm shelter for organisms to settle and develop
 Marine organisms can withstand strong ocean currents
Changing ocean current
Water flow pattern is changed which provides
calm water and resting area for fish
Providing additional food
• deflection of currents can result in the
concentration of plankton
• additional food source is provided for
young fish
• reef structures provides a ready
source of food for fish and other
marine life.
Providing shelter
• increase the habitat diversity under
water
 diversity of species also increase
• provide hiding place to prevent
predation
Discussion
Many fishery scientists however challenge this view and consider artificial reefs to
be a waste of money, which do little to enhance fishery resources. Some go further
and said that artificial reefs actually do more damage than good by aggregating fish,
which makes them easier to catch, thus causing over-fishing. They argue that
improvement in fish stocks should be achieved by establishment of marine
protected areas rather than through Artificial Reefs programmes.
So, is it effective to enhance
production by using artificial reefs?
Artificial Reefs programme has established the no fishing areas, or 'notake' areas
artificial reefs can be deployed in areas of open water away from the
heavily fished natural rocky shores
artificial reefs will also prevent bottom trawling which is a non-selective
method of fishing
long run trawlers will benefit from artificial reef deployment since catches
in waters adjacent to artificial reef areas will be enhanced
seabed nature can be modified
e.g. the seabed of Ho Hai Wan changes form muddy to coarser sediment
which is beneficial for the settlement of corals
Background of artificial reefs project in Hong Kong
Marine resources in Hong Kong have been declining in recent years because of:
• over-fishing
• foreshore
• seabed developments
• water pollution
In July 1995, the Hong Kong Government announced a HK$108 million Artificial
Reef Project aimed at enhancing local marine resources.
Types of materials used as artificial reefs including
• Vessels
• Concrete
• Quarry rock
• tyre reefs
The applications of artificial reefs in Hong Kong
Goals of the artificial reefs project:
To enhance local marine and fishery resources.
To rehabilitate degraded habitats.
To protect spawning and nursery grounds, and marine protected areas.
To enhance habitat quality in open seabed areas.
To promote biodiversity in HK’s marine environment.
The applications of artificial reefs in Hong Kong
2.
1.
4.
5.
6.
3.
Areas involved in the artificial reefs project
The applications of artificial reefs in Hong Kong
Phase 1--- Hoi Ha Wan Marine Park
Yan Chau Tong Marine Park
The applications of artificial reefs in Hong Kong
The applications of artificial reefs in Hong Kong
Objective:
 Prevention of trawling
 Enhancement of habitat quality and marine resources
Type of artificial reefs used:
* boats
* tyre
* concrete coated tyre
* quarry rock
* pre- cast concrete
* biofilter core
One of the artificial reefs site from
Yan Chau Tong Marine Park
The applications of artificial reefs in Hong Kong
boat
Three layer pyramid tyre
biofilter
Quarry rock
Pre- cast concrete
Phase 2 --- Outer Port Shelter
Long Harbour
The applications of artificial reefs in Hong Kong
The applications of artificial reefs in Hong Kong
Objective:
• Prevention of trawling
• Enhancement of habitat quality and marine resources
Type of artificial reefs used:
* boat with tyre
The applications of artificial reefs in Hong Kong
* redundant pier
* Dolphin fender
* Pre-cast concrete module
The applications of artificial reefs in Hong Kong
Concrete-coated container
River barge
Result of the Artificial Reefs Project
 number of fish species increased from 40 in 1998 to over 220 species in
2003
bream
snapper
 concrete was acceptable as an artificial reef building material
 enhance abundance, biomass, diversity and species richness of fish
 effective fish aggregating device and will aggravate the over-fishing problem
in an open access system
 can improve the water quality
 economic value of the fishery could increase by as much as 30% after 15
years
http://www.artificial-reef.net/English/5_3.htm#
Conclusio
n
In fact, a carefully planning of artificial reefs project can help to
solve many problems, not only to prevent over-fishing, it can also
enhance the fisheries resources, and the diversity of species. With
the no fishing agreement and the marine protected areas, more
valuable fishes can be protected. The case in Hong Kong is a quite
successful example.
Reference
• http://www.artificial-reef.net/main2.htm#
• http://www.hku.hk/ecology/porcupine/por18/reefs.htm
• http://www.njscuba.net/reefs/index.html
~ End ~