The principles and values of artificial reefs and its applications in Hong Kong

1. The principles and values of artificial reefs and its applications in Hong Kong Yu Wing Yan 6B(31)

2. Artificial Reefs • 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

3. How do artificial reefs enhance fishery production? • increase surface area • providing substrate • changing ocean current • providing additional food source • providing shelter

4. 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

5. 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

6. Changing ocean current Water flow pattern is changed which provides calm water and resting area for fish

7. 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.

8. Providing shelter • increase the habitat diversity under water •  diversity of species also increase • provide hiding place to prevent predation

9. 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?

10. Artificial Reefs programme has established the no fishing areas, or 'no- take' 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

11. 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

12. 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

13. 2. 1. 4. 5. 6. 3. Areas involved in the artificial reefs project The applications of artificial reefs in Hong Kong

14. Phase 1--- Hoi Ha Wan Marine Park Yan Chau Tong Marine Park The applications of artificial reefs in Hong Kong

15. The applications of artificial reefs in Hong Kong

16. 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

17. boat Three layer pyramid tyre biofilter Quarry rock Pre- cast concrete

18. Phase 2 --- Outer Port Shelter Long Harbour The applications of artificial reefs in Hong Kong

19. The applications of artificial reefs in Hong Kong

20. Objective: • Prevention of trawling • Enhancement of habitat quality and marine resources • Type of artificial reefs used: • boat with tyre • redundant pier The applications of artificial reefs in Hong Kong

21. Dolphin fender • Pre-cast concrete module The applications of artificial reefs in Hong Kong

22. Concrete-coated container River barge

23. 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#

24. Conclusion 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.

25. 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 ~