58
LAMARR B. TROTT
crustaceans, 3% squids, and 1% other marine animals. To catch this amount, 56,000 local fishermen worked 6,800 fishing vessels and this does not include the catches sold by fishermen based in other localities than Hong Kong. Half of the yield every year is supplied by trawling vessels, while long line, purse seining, and gill netting techniques are of less importance. A modernization of equipment, enabling trawlers and long line vessels to go farther afield for their catches will increase the yield and make Hong Kong more self-sufficient. This process is gradually taking place, but needs speedier implementation,
Marine Conditions in General
For a background of conditions existing in Hong Kong, let us first look at the marine environment in general, and in other areas of the world. When one first observes the sea in a tropical climate, he is immediately aware of a tremendous diversity of organisms. The tropics, both on land and in the sea, is a plethora of bizarre and varied living forms. It is a well-known biological fact that although the absolute number of individuals present in a tropical vs. a temperate area may be the same, the number of species is far greater in the tropics*.
The most important factor in determining the distribution of biological forms, therefore, appears to be temperature. Many marine organisms are definitely limited by temperature, and corals which are exclusively marine are an excellent example. Reef-building corals usually exist only in a wide tropical belt in which the temperature does not fall below 20°C for any long period during the year. Another important physico-chemical factor is salinity, or saltiness of the water. Salinity is actually a measure of all the salts in the water, although the major one is sodium chloride. The actual amount of salt determines the biologically important osmotic pressure and thus is often a limiting factor. Take echinoderms, like starfishes, sea urchins and the like; they are strictly marine, and are not even found in moderately brackish water. Other forms, called chaetognaths, or arrow worms, are so narrowly tolerant of change in salt content that one can tell the saltiness of the water by what species of
* Mayr, 1963.
58
LAMARR B. TROTT
crustaceans, 3% squids, and 1% other marine animals. To catch this amount, 56,000 local fishermen worked 6,800 fishing vessels and this does not include the catches sold by fishermen based in other localities than Hong Kong. Half of the yield every year is supplied by trawling vessels, while long line, purse seining, and gill netting techniques are of less importance. A modernization of equipment, enabling trawlers and long line vessels to go farther afield for their catches will increase the yield and make Hong Kong more self-sufficient. This process is gradually taking place, but needs speedier implimentation,
Marine Conditions in General
For a background of conditions existing in Hong Kong, let us first look at the marine environment in general, and in other areas of the world. When one first observes the sea in a tropical climate, he is immediately aware of a tremendous diversity of organisms. The tropics, both on land and in the sea, is a plethora of bizarre and varied living forms. It is a well known biological fact that although the absolute number of individuals present in a tropical vs. a temperate area may be the same, the number of species is far greater in the tropics*.
The most important factor in determining the distribution of biological forms, therefore, appears to be temperature. Many marine organisms are definitely limited by temperature, and corals which are exclusively marine are an excellent example. Reef-building corals usually exist only in a wide tropical belt in which the temperature does not fall below 20°C. for any long period during the year. Another important physico-chemical factor is salinity, or saltiness of the water. Salinity is actually a measure of all the salts in the water, although the major one is sodium chloride. The actual amount of salt determines the bio- logically important osmotic pressure and thus is often a limiting factor. Take echinoderms, like starfishes, sea urchins and the like they are strictly marine, and are not even found in moderately brackish water. Other forms, called chaetognaths, or arrow worms, are so narrowly tolerant of change in salt content that one can tell the saltiness of the water by what species of
* Mayr, 1963.
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