The only marine reptiles in Hong Kong are the three species of chelonians which are sea turtles, the Green Sea Turtle (Chelonia mydas), the Olive Ridley Sea Turtle (Lepidochelys olivacea) and the Leatherback Sea Turtle (Dermochelys coriacea) as well as the occasional sighting of one species of sea snake Hydrophis cyanocinctus which has been seen swimming in waters near to the shore (Karsen et al 1998). Sea turtles breed by laying their eggs on sandy beaches at night. Breeding adults return to nest at the beach where they were hatched and then return to the same beach in two or more years time (McGilvray and Geermans 1997). During their breeding season, the turtles migrate from their feeding ground to mate in shallow waters off their nesting beaches. The female comes ashore two or more times a season on an average of every three years to lay eggs in a nest cavity on the beach (McGilvray and Geermans 1997; AFCD Homepage).

Of an estimated 1,800 species of fish on the continental shelf of the South China Sea (AFCD webpage, http://www.info.gov.hk/afd/conserv/ fauna.htm), over 300 species of marine and estuarine fishes are found in Hong Kong waters (ERM 1998a). Based on fishermen's reported catches, it appears that the clupeids (herrings, shads, and sardines), carangids (jacks and pompanos) and sciaenids (croakers and drums) are the dominant groups in Hong Kong (ERM 1998a). As discussed in Paragraphs 3.3.2.57 - 3.3.2.810 - Agriculture and Pressures on Capture Fisheries Resources, due to a combination of fishing pressure, loss of habitat and pollution impacts, the species composition of Hong Kong's fish populations over the past few decades has evolved from large, slow-growing valuable, reef-associated fishes, to smaller, fast-growing, low value, water column fishes. One of the most vulnerable of Hong Kong's marine fishes is the spotted seahorse, Hippocampus kuda, which has been observed in several areas of Hong Kong including Lai Chi Wo, Double Haven and Sheung Sze Wan, Sai Kung but is considered rare (ERM, unpublished data). There are no species of fish protected under either the Marine Parks Ordinance or the Wild Animals Protection Ordinance.

An ecosystem model of Hong Kong's marine food chain was constructed based on a comprehensive review of existing literature and showed that well over half of the total biomass was derived from plankton and zoobenthos, such as marine worms. It was estimated that marine fishes, including sharks and rays, pelagic (ie water column) and demersal (ie bottom-associated) fishes composed less than 5% of the total biomass. The absolute biomass of Hong Kong compared unfavourably with the marine environment off the western coast of Canada, but appeared comparatively healthy in relation to an estimate for the central South China Sea. However, it should be noted that open ocean environments are known to support lower biomass levels than nutrient rich coastal environments such as Hong Kong (ERM 1998e).