A total of 15 new reef fish species to Hong Kong were recorded in these surveys, and these comprise nine families, namely Blennidae (3 species), Apogonidae (2 species), Gobiidae (2 species), Holocentridae (2 species), Muraenidae (2 species), Acanthuridae (1 species), Gobiesocidae (1 species), Pomacentridae (1 species) and Serranidae (1 species). New species to Hong Kong were regarded as those which have neither been documented on hk-fish.net (2018) – a government maintained marine fish database of Hong Kong, or in earlier reef fish studies in Hong Kong (Ni and Kwok 1999; Sadovy and Cornish 2000; To et al. 2013; To and Shea 2016).

Chromis fumea (Tanaka, 1917) family: Pomacentridae

An individual of Chromis fumea (Tanaka, 1917) (Fig. 2) was spotted swimming among a school of Chromis notata (Temminck & Schlegel 1843) in the water column above boulders at about 8 m in depth at Ping Min Chau (22°18′41”N, 114°19′04″E) on 10th July 2016, in day time. The individual was about 5 cm in total length. Individuals of Chromis fumea were since observed several more times around Hong Kong, also swimming among schools of Chromis notata. As Chromis notata is one of the most common reef fish species in Hong Kong, and their appearance and behavior are very similar to Chromis fumea (To and Shea 2017), it is possible that previous occurrences of Chromis fumea were missed by divers. The native range of Chromis fumea covers the Indo-West Pacific, mainly the western Pacific region, including Australia, Indonesia, Japan, South Korea, Lord Howe Islands, Malaysia, mainland China, New Caledonia, New Zealand, Norfolk Islands, Ryukyu Islands, Taiwan and Vietnam (Fishbase 2018a; Liu 2008; Wu 2012;)

Fig. 2 An individual of Chromis fumea among a school of Chromis notata observed at Ping Min Chau Full size image

Pherallodus indicus (Weber, 1913) family: Gobiesocidae

An individual of Pherallodus indicus (Weber, 1913) (Fig. 3), about 2 cm in total length, was spotted and photographed at Tai Hang Tun (22°17′28”N, 114°18′22″E) at around 2 m in depth on 27 Jul 2016 in day time. The location was exposed to strong wave action and barnacles and sea urchins were commonly found along that rocky shore. The clingfish was first found lying on the rock surface near a sea urchin. As the surveyor approached, the clingfish hid beneath the sea urchin and when the sea urchin started to move, the clingfish moved alongside it. Pherallodus indicus is naturally found in the Western Central Pacific region, and has been reported from Indonesia, Japan, Lord Howe Islands, mainland China, New Caledonia, Pitcairn, Taiwan, Tonga and Tuamotu Islands (Fishbase 2018b; Liu 2008; Wu 2012).

Fig. 3 An individual of Pherallodus indicus observed at Tai Hang Tun in shallow water at the rocky shore Full size image

Petroscirtes springeri Smith-Vaniz, 1976 family: Blennidae

Two individuals of Petroscirtes springeri Smith-Vaniz, 1976 (Fig. 4) and subsequently four individuals of this species were spotted on 16 Sept and 29 Oct 2016 respectively at Basalt Island (22°18′31”N; 114°21′52″E) in day time. All these observations involved individuals of Petroscirtes springeri at about 7 cm in total length and were made at Basalt Island at about 16–18 m in depth. The location was a rocky reef and the habitat where Petroscirtes springeri were observed was a mix of boulder, rubble and sand with occasional small gorgonian. These individuals of Petroscirtes springeri were observed to hover above the seabed in a noticeably more static manner than another commonly observed blenny species Petroscirtes breviceps, which tends to be in contact with the substrate or moving actively over it. Petroscirtes springeri is found in the northwest Pacific, including mainland China, Japan and Taiwan, (Fishbase 2018c; Liu 2008; Wu 2012).

Fig. 4 An individual of Petroscirtes springeri recorded at Basalt Island over a mix of boulder, rubble and sand habitat Full size image

Myripristis botche Cuvier, 1829 family: Holocentridae

A single individual of Myripristis botche Cuvier, 1829 was spotted hovering around a dead coral in the middle of a sandy bottom habitat at around 10 m in depth during day time on 18 Sep 2016, at South Ninepin Islands (22°15′33”N; 114°20′57″E) (Fig. 5). This soldierfish individual, estimated to be around 20 cm in total length, was observed to remain at the same dead coral for over an hour but would immediately retreat into the dead coral when a torch was used to point to the fish. This species is naturally found in the Indo-West Pacific, including Australia, Brunei Darsm, India, Indonesia, Japan, South Korea, mainland China, Malaysia, Maldives, Mauritius, Mayotte, Mozambique, New Caledonia, Ogasawara Islands, Philippines, Ryukyu Islands, Seychelles, Somalia, South Africa, Sri Lanka, Taiwan, Thailand, Vanuata and Vietnam (Fishbase 2018d; Liu 2008; Wu 2012).

Fig. 5 An individual of Myripristis botche observed to hover around a dead coral at South Ninepin Islands Full size image

Valenciennea wardii (Playfair, 1867) family: Gobiidae

An individual of Valenciennea wardii (Playfair, 1867) was recorded on 19 Sep 2016 at South Ninepin Islands (22°15′33”N; 114°20′57″E) (Fig. 6), at about 8 m in depth in day time. The goby was observed to be wary of the surveyor and maintained a distance from the surveyor by moving around over the sandy and muddy bottom. The goby individual was estimated to be around 11 cm in total length. This species is found in the Indo-Pacific, including Andaman Islands, Australia, Indonesia, Japan, mainland China, Maldives, Papua New Guinea, Philippines, Seychelles, Sudan, Taiwan, Tanzania, Thailand and Vietnam (Fishbase 2018e; Liu 2008; Wu 2012).

Fig. 6 An individual of Valenciennea wardii recorded at South Ninepin Islands over sandy muddy bottom Full size image

Myripristis hexagona (Lacepède, 1802) family: Holocentridae

A single individual of Myripristis hexagona (Lacepède, 1802) was observed swimming around boulders at a rocky reef at night, at Basalt Island (22°18′31”N; 114°21′49″E) (Fig. 7), on 24 Sep 2016. The soliderfish individual was around 20 cm in total length and was found at about 15 m in depth. Myripristis hexagona is distributed in the Indo-Pacific, and found in around 35 countries or territories including Indonesia, Japan, mainland China, Malaysia, Ogasawara Islands, Philippines, Ryukyu Islands, and Taiwan (Fishbase 2018f; Liu 2008; Wu 2012).

Fig. 7 An individual of Myripristis hexagona observed swimming around boulders at night at Basalt Island Full size image

Pseudanthias squamipinnis (Peters, 1855) family: Serranidae

Four individuals of Pseudanthias squamipinnis (Peters, 1855) were observed at Fo Siu Pai (22°16′33”N; 114°21′35″E) in day time on 10 Jun 2017, at around 16 m in depth (Fig. 8). These four individuals were observed among a school of Chromis notata (Temminck & Schlegel, 1843), hovering around boulders where barnacles and soft corals abound. This school of anthias and damselfish were seen to actively feed on micro-organisms brought in by the current at that location. The anthias individuals were alert of surveyors and were seen to retreat into rock crevices or hide among spines of sea urchins. This species is distributed in the Indo-West Pacific and found in about 39 countries or territories including Indonesia, Japan, South Korea, mainland China, Ogasawara Islands, Philippines, and Taiwan (Fishbase 2018g; Liu 2008; Wu 2012).

Fig. 8 Individuals of Pseudanthias squamipinnis observed at Fo Siu Pai, hovering around boulders Full size image

Xiphasia setifer Swainson, 1839 family: Blennidae

An individual of Xiphasia setifer Swainson, 1839 was observed on 3 Jun 2017 in day time at about 8 m in depth, over sandy to muddy bottoms off rocky areas at Bluff Island (22°19′27”N; 114°21′09″E) (Fig. 9). This blenny was observed to occupy a burrow close to an individual of a bandfish species (Acanthocepola sp.). The blenny stayed mostly within the burrow but occasionally came out to expose part of the body outside the burrow. The total length of the blenny therefore could not be estimated but the exposed body part was about 40 cm in length. The same species, likely the same individual, was spotted again near the same area and habitat on 16 Jun 2017. Xiphasia setifer is found in the Indo-West Pacific, including Andaman Islands, Australia, Bahrain, India, Indonesia, Japan, Kuwait, Lord Howe Islands, Madagascar, mainland China, Malaysia, Mauritius, New Caledonia, Oman, Papua New Guinea, Philippines, Qatar, Saudi Arabia, South Africa, Taiwan, Thailand, UAE and Vanuata (Fishbase 2018h; Liu 2008; Wu 2012).

Fig. 9 An individual of Xiphasia setifer observed occupying a burrow over sandy to muddy bottoms off rocky areas at Bluff Island Full size image

Cheilodipterus species family: Apogonidae

An individual of a Cheilodipterus species was observed and photographed at Clearwater Bay (22°16′19”N; 114°18′07″E) (Fig. 10), on 29 Jul 2017 in day time. The observed individual was about 10 cm in total length, found to be hiding near rocky reefs and occasionally swam along the margin of the reef adjacent to the sandy bottom, at about 7 m in depth. The individual was observed to occasionally mix into a group of about 10 similarly-sized Ostorhinchus fleurieu Lacepède, 1802. Based on the photograph, the whitish tail base and the brown stripes being generally thicker than the whitish interspaces on the body indicate the individual being either Cheilodipterus intermedius (Gon, 1993) or Cheilodipterus macrodon (Lacepède, 1802) (Allen and Erdmann 2012; Allen et al. 2015). Cheilodipterus intermedius is similar to Cheilodipterus macrodon, but the former is generally slenderer in shape and has a more pronounced whitish area on caudal fin base without a hint of black bar (Allen and Erdmann 2012; Allen et al. 2015). While it is challenging to accurately identify the individual based on the single observation and photographs taken, either of the speculated species would be a new record for Hong Kong, where Cheilodipterus artus (Smith, 1961) is the only Cheilodipterus species recorded so far (hk-fish.net 2018; Sadovy and Cornish 2000; To et al. 2013; To and Shea 2016). While Cheilodipterus macrodon is more widespread and found in about 55 countries or territories in the Indo-Pacific from Red Sea and East Africa to Pitcairn, north to the Ryukyu Islands, south to Lord Howe Islands and Rapa (Fishbase 2018i; Liu 2008; Wu 2012), Cheilodipterus intermedius is relatively more restricted and is reported from around 10 countries or territories in the Western Pacific from Japan south to Australia east to Solomon Islands (Fishbase 2018j; Liu 2008; Wu 2012).

Fig. 10 An individual of Cheilodipterus species observed at Clearwater Bay near a rocky reef Full size image

Aspidontus taeniatus Quoy & Gaimard, 1834 family: Blennidae

An individual of Aspidontus taeniatus Quoy & Gaimard, 1834 was recorded at Pak Pai (22°18′25”N; 114°18′21″E) on 20 Aug 2017 in day time (Fig. 11). The blenny individual was about 10 cm in total length and was seen swimming around boulder and rubble habitats at around 5 m in depth. This blenny was noted to swim alongside an individual of Labroides dimidiatus (Valenciennes, 1839), which the blenny mimics in body colour, pattern and even movement (Kuwamura 1983). Aspidontus taeniatus is found in the Pacific Ocean covering about 31 countries and territories including Australia, Indonesia, Japan, mainland China, Philippines and Taiwan (Fishbase 2018k; Liu 2008; Wu 2012).

Fig. 11 An individual of Aspidontus taeniatus at the front and Labroides dimidiatus at the back, at Pak Pai around boulder and rubble habitat Full size image

Tomiyamichthys oni (Tomiyama, 1936) family: Gobiidae

A single individual of Tomiyamichthys oni (Tomiyama, 1936) was found in rubble habitats at depths of about 15 m (Fig. 12), in southern waters (22°12′20”N; 114°15′38″E) adjacent to Shek O on 30 Apr 2018 in day time. The goby, which was about 10 cm in total length, was alert of surveyors and stayed close to the entrance to a burrow, and the goby immediately retreated into the burrow when the surveyor approached. This species is found in the Western Pacific including Indonesia, Japan, mainland China, Malaysia, New Caledonia, Ogasawara Islands, Palau, Papua New Guinea, Ryukyu Islands and Taiwan (Fishbase 2018l; Liu 2008; Wu 2012; Shao 2018).

Fig. 12 An individual of Tomiyamichthys oni observed in southern waters adjacent to Shek O in rubble habitat Full size image

Gymnothorax albimarginatus (Temminck & Schlegel, 1846) family: Muraenidae

An individual of Gymnothorax albimarginatus (Temminck & Schlegel, 1846) (Fig. 13) was spotted in day time near the edge of the rocky reef at Sharp Island (22°21′39”N, 114°17′28″E), at about 10 m in depth. The individual was estimated to be about 60 cm in total length and was observed to rest with the body curved over the sandy bottom. It then swam around, apparently to look for shelter. The species is found in the Indo-Pacific, including Indonesia, Japan, South Korea, mainland China, New Caledonia, Samoa and Taiwan (Fishbase 2018m; Liu 2008; Wu 2012).

Fig. 13 An individual of Gymnothorax albimarginatus observed actively swimming and looking for shelter at Sharp Island Full size image

Rhabdamia gracilis (Bleeker, 1856) family: Apogonidae

Two individuals of Rhabdamia gracilis (Bleeker, 1856) were observed swimming towards the light source of the divers during a night dive at Clearwater Bay (22°16′19”N; 114°18′07″E) on 1 Jul 2018 (Fig. 14). The two individuals were observed to swim closely to each other over rocky substrate, at about 5 m in depth. Both individuals were estimated to be about 5 cm in total length. This species is found in the Indo-West Pacific, including Mauritius, Mozambique, Seychelles, South Africa, Tanzania, Andaman Islands, Cocos Islands, India, Indonesia, Japan, mainland China, Malaysia, Maldives, Philippines, Ryukyu Islands, Taiwan, Vietnam, Australia, Fiji, Marshall Islands, Micronesia, New Caledonia, Palau and Papua New Guinea (Fishbase 2018n; Liu 2008; Wu 2012).

Fig. 14 An individual of Rhabdamia gracilis observed at night over rocky substrate at Clearwater Bay Full size image

Echidna polyzona (Richardson, 1845) family: Muraenidae

An individual of Echidna polyzona (Richardson, 1845) was observed during night time at Clearwater Bay (22°16′19”N; 114°18′07″E) on 1 Jul 2018 (Fig. 15). The moray only protruded its head outside of the crevice at a rocky reef at about 6 m in depth. The size of the moray could not be easily noted as most of its body was hidden within the crevice, but it was likely to be about 60 cm in total length. This species is naturally found in the Indo-Pacific, covering about 41 counties/territories and territories, including India, Indonesia, Japan, mainland China, Philippines, Ryukyu Islands, Taiwan and Vietnam (Fishbase 2018o; Liu 2008; Wu 2012).

Fig. 15 An individual of Echidna polyzona spotted at night hiding within rocky reef at Clearwater Bay Full size image

Naso unicornis (Forsskål, 1775) family: Acanthuridae

An individual of Naso unicornis (Forsskål, 1775) was spotted in day time at Pak Lap Tsai (22°21′112”N; 114°22′05″E) swimming quickly near a rocky reef at about 2 m in depth on 7 Jul 2018 (Fig. 16). The individual, which was about 20 cm in fork length, was observed to actively swim away from the surveyor. Naso unicornis is found is in the Indo-Pacific covering about 59 countries and territories. These include India, Indonesia, Japan, mainland China, South Korea, Malaysia, Ogasawara Islands, Philippines, Ryukyu Islands, Taiwan and Vietnam (Fishbase 2018p; Liu 2008; Wu 2012).