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Hong Kong Corals & the Associated Marine Life

Hong Kong Corals & the Associated Marine Life

> Other marine organisms


Phylum Chordata


Phylum Chordata includes both vertebrates and invertebrates, comprising three sub-phyla: Urochordata (Sea squirts & Salps), Cephalochordata and Vertebrata (vertebrates)

Sea Squirts (Sub-phylum Urochordata, Class Ascidiacea)


Sea Squirt 3


Sea squirts are the invertebrates related most closely to vertebrates, though they are most often confused with sponges, the simplest living group of multicellular organisms. Some sea squirts are entirely pelagic while those commonly found in coral areas are benthic, in both solitary and colonial forms.

Both solitary and colonial sea squirts have a body wall with two openings, the oral and cloacal siphons. Long bundles of muscle fibres in the body wall can contract the body quickly to produce a fine stream of water coming in and  going out the siphons. Within the body wall are the branchial sac for gas exchange, food-gathering structures, stomach, circulatory system, gonads and other internal organs.

Reef Fish (Sub-phylum Vertebrata)


There are four major classes of fishes alive today, the lampreys (Cephalaspidomorphi), the hagfish (Pteraspidomorphi), the cartilagenous fish (Chondrichthyes) and the bony fish (Osteichthyes). Only the cartilagenous fish (sharks and rays) and the bony fish (most other fish) inhabit reef. There are about 350 species of shark and 500 rays worldwide. Among the estimated 23,000 species of bony fish, around 13,000 are marine.

Reef fish are those that spend part or all of their lives on or close to areas of hard substrata. Most "reefs" in Hong Kong are rocky although there are a number of small coral communities, particularly in eastern waters. They provide food and shelter to the fish that inhabit them.  

The biodiversity of reef fish in Hong Kong is relatively high, being greater than that of Hawaii for instance. It is similar to other locations in the South China Sea such as Hainan Island. Hong Kong has an interesting mix of tropical species that are distributed widely throughout the Indo-Pacific and temperate species which mostly occur from Hong Kong north to Japan and Korea. No reef fish are known to be endemic to Hong Kong.

Although the diversity of local reef fish is high, some of them such as the surgeon and triggerfish that are normally common on coral reefs are rare now. This is likely because local conditions are not suitable for them, or there are few larvae of these species settling onto local reefs. Reef fish are heavily dependent on the continued survival of hard corals. Having healthy coral communities in local waters is essential for the continual survival of the reef fish.


Doederlein's Cardinalfish

 Doederlein's Cardinalfish
  Apogon   doederleini   (Apogonidae)

There are 4-5 narrow brownish strips on the whitish to pinkish body. Juveniles occur in schools, often found between coral heads or large rock crevices. This species is common in local waters.

Broadbanded Cardinalfish

  Broadbanded Cardinalfish
      Apogon  fasciatus       (Apogonidae)

Cardinalfish are nocturnal, remaining close to shelter and in schools by day, and dispersing to feed at night. They are also interesting as the males incubate the eggs in their mouths after fertilisation until the larvae hatch. Broadbanded cardinalfish inhabit areas of silt and sand near reefs, often in large schools.

Longfin Grouper Epinephelus quoyanus

Longfin Grouper 

 Epinephelus  quoyanus  (Serranidae)



Blue-blotch Butterfly Fish
Blue-blotch Butterfly Fish
 Chaetodon  plebeius  (Chaetodontidae)

This species of butterfly fish was recently first recorded from local waters. It is quite rare, inhabiting rich areas of hard coral as it feeds mainly on live polyps of Acropora corals. Hong Kong is probably close to the northern limit for this tropical species along the coast of mainland China.

Mirror Butterfly Fish Chaetodon speculum
Mirror Butterfly Fish
 Chaetodon  speculum  (Chaetodontidae)

This species looks similar to C.  plebeius, but it doesn't have a black spot at the tail base. It is common in Port Shelter.

Brownband Butterfly Fish
Brownband Butterfly Fish
 Chaetodon  modestus 

It is a distinctive fish, with two broad brownish-yellow bars on each side of the silvery-white body. This species is one of the most abundant butterfly fish in Hong Kong. Though this butterfly fish is a deep water species in other regions, it can be found in local shallow boulder areas.

Threadfin Butterfly Fish
Threadfin Butterfly Fish
 Chaetodon  auriga  (Chaetodontidae) 

This species is unmistakable with the diagonal bands on the body and the black spot at the posterior margin. It is widespread and moderately abundant below waters of 3 m in depth.

Lined Butterfly Fish Chaetodon lineolatus
Lined Butterfly Fish
 Chaetodon  lineolatus

This species has many fine black vertical lines covering the body. The dorsal, caudal and anal fins are bright yellow. It is moderately abundant in coral areas of Port Shelter.

Blackbacked Butterfly Fish
Blackbacked Butterfly Fish
 Chaetodon  melannotus  (Chaetodontidae)

It has diagonal black lines on both sides of the white body and a broad black near the dorsal fin. This fish was found at Bluff Island , probably occurring from Lamma Island to Ping Chau.

Eightband Butterfly Fish
Eightband Butterfly Fish
 Chaetodon  octofasciatus  

It is a juvenile hiding among the branches of stony coral Acropora. It is distinctive with the 8 vertical bars on the yellow body. This species is moderately abundant in areas of Acropora corals.

Hong Kong Butterfly Fish
Hong Kong Butterfly Fish
 Chaetodon  wiebeli  (Chaetodontidae)
Long-fin Bannerfish Heniochus acuminatus
Long-fin Bannerfish 
 Heniochus  acuminatus  (Chaetodontidae)
Chinese Demoiselle Neopomacentrus bankieri
         Chinese Demoiselle             Neopomacentrus  bankieri        (Pomacentridae)      

This is the most abundant fish inhabiting coral communities after some of the gobies. It was described as a new species from a specimen collected in Hong Kong in the early 1800s. The new species was named after R.A. Bankier, a surgeon in the British Navy, who collected the specimen. Although the Chinese demoiselle is known from other regions, it only seems to be common here.

Bengal Sergeant Abudefduf bengalensis
Bengal Sergeant 
 Abudefduf  bengalensis  (Pomacentridae)

On the sides of its yellow body, seven bands can be found, which are distinctly narrower than the spaces between them. This species is common in shallow boulder and coral areas.

Yellowtail Clownfish Amphiprion clarkii
 Yellowtail Clownfish 
 Amphiprion  clarkii  (Pomacentridae)

Its body colour is highly variable throughout its range, from orange , brown to black. The three white bars on the head and body is distinctive. This species is common and always found associated with the sea anemone  Entacmaea  quadricolor.


Blue-stripe Angelfish Chaetodontoplus septentrionalis
     Blue-stripe Angelfish     Chaetodontoplus  septentrionalis (Pomacanthidae)
Blue-ringed Angelfish Pomacanthus annularis
    Blue-ringed Angelfish    Pomacanthus  annularis (Pomacanthidae)
Cockerel Wrasse Pteragogus enneacanthus
           Cockerel Wrasse           Pteragogus   enneacanthus  (Labridae)

This cryptic species remains close to cover and inhabits semi-exposed rocky shores with clear water and some hard corals. The cockerel wrasse probably feeds on benthic invertebrates. Unlike many wrasses, both males and females have similar colouration, but males develop two "horns" in front of the dorsal fin. The wrasses (Labridae) are one of the most diverse families of local reef fish, more than 30 species have been recorded.

Blue-streak Cleaner Wrasse
   Blue-streak Cleaner Wrasse   
 Labroides  dimidiatus 

It feeds on the crustacean ectoparasites and mucus of fish at specific cleaning stations. To attract "customers", the cleaner wrasse moves up and down at its station during daytime.

Chinese Wrasse Halichoeres tenuispinis
                Chinese Wrasse                 Halichoeres   tenuispinis     (Labridae)  
Stellar Rock-hopper Entomacrodus stellifer lighti
        Stellar Rock-hopper      Enfomacrodus  stellifer  lighti (Blenniidae)

This inter-tidal blenny is extremely abundant along exposed rocky shores such as at the Cape d'Aguilar Marine Reserve. It occurs only at a few metres depth, hiding in crevices and empty barnacle shells when threatened.