Further notes on freshwater fish of Hong Kong
Further Notes on Freshwater Fish of Hong Kong
by K.W. CheungIn the last issue of Porcupine!, there were a number of articles on local freshwater fish by Professor Dudgeon and Bosco Chan. It seems that freshwater fish, which have not received much attention in the past, have become a wildlife group of concern. To continue the heated I discussion, I would like to contribute some more information on local freshwater fish.
Follow-up:
Eleotris species
Another specimen of the Eleotris species I described in Porcupine! 17 was collected in a stream estuary at Pak Nai, NWNT, on 6 January 1999. Fish of similar appearance were seen in various estuaries in Lantau such as Tung Chung and Mui Wo. It is very likely that the fish is the juvenile of Eleotris oxycephala.Rhodeus ocellatus
Bosco Chan in Porcupine! 19 opined that the bitterling occurring in Kam Tin River should be Rhodeus sinensis on the basis of body depth : body length ratio and colour of specimens in alcohol. It seems to me that the specimens collected by Bosco Chan at that time might be juveniles which would have more elongated bodies. Based on my observations of living specimens, a few of which I have kept for over one year, the fish should be R. ocellatus. One distinct feature of this species is the presence of two dark stripes behind the operculum (Pan 1991). This feature is more prominent in the male during breeding time. As regards the body size ratio, juveniles have more elongated bodies with a greater size ratio. As the fish grow, the increase in body depth is greater than the increase in body length, and the size ratio is lowered to about 2. This again is more prominent in males, which are larger than the females.Concerning the distribution of the bitterling, the fish are also found in two other sites apart from Kam Tin River. My colleague observed some large specimens of this fish in a site near Shatin a few years ago. Our recent site visit on 9 June 1999 found that the bitterling still occurs there, but only small specimens were seen. In addition, my field staff found the co-existence of the fish and its host, the swan mussel Anodonta woodiana, in a stream in Tai Lam Country Park on 19 March this year. However, the abundance of both organisms seems not very high.
New findings:
Taenioides cirratus
A specimen of this eel goby was collected at the estuary of Tai Shui Hang, near Pak Nai. It has an eel-like appearance and is about 20cm in length. The fish burrows in estuarine mudflats. Scales are absent and its body is covered by mucus secreted by glands alongside the body. Dorsal fin is long and many-rayed. Pelvic fins united to form a sucker as in the gobies. Although it is an estuarine fish, it can survive well in a freshwater aquarium. This fish was not described by Chong and Dudgeon (1992) and could be considered as a new freshwater record.Channa striata
Some newly hatched orange coloured fry of a Channa species were collected in a nullah at Pak Nai last year. The fry grew very rapidly in aquarium and maintained their interesting orange colour. Dark coloured chevron-shaped bars pointing forward began to develop when the fish was over 5cm in length. Such a colour pattern indicated that the fish should be Channa striata. Two young specimens of about 6cm in length were caught in a stream near Man Kam To recently. They have similar colour patterns but with a dark spot at the end of the dorsal fin. Apart from the colour pattern, this fish differs from the local snakehead Channa maculata in having a more compressed head.Channa striata is an important food fish in Southeast Asia and has been introduced to China (Kottelat et al 1993). However, this species was not recorded in Guangdong by Pan (1991). This fish has also been introduced to the local market and is known as Thailand snakehead. The specimens collected were very likely escapes from local fish farms since both sites where this species were found are near to active fish ponds. However, the fish seems to have naturalized locally and specimens have been seen in other waterbodies by my colleague. The occurrence of newly hatched fry indicated the fish could breed locally.
Chong, D.H. and D. Dudgeon (1992). Hong Kong stream fishes: an annotated checklist with remarks on conservation status. Memoirs of the Hong Kong Natural History Society 19: 79-112.
Kottelat, M., A.J. Whitten, S.N. Kaitikasari and S. Wirjoatmodjo (1993). Freshwater Fishes of Western Indonesia and Sulawesi. Periplus Editions Limited. Indonesia. pp 230-231.
Pan. J.H. (1991). The Freshwater Fishes of Guangdong Province. Guangdong Science and Technology Press. China
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More of the fishy things!
by Bosco ChanI am writing to make some (possible) corrections on taxonomy to my article in Porcupine! no.19, and talk a bit more about fish until you guys tell me to stop! In the previous article titled "Hong Kong's Freshwater Fish: Who Cares?!?", I noted that the bitterling found in Kam Tim is Rhodeus sinensis based on a recent paper by two Japanese fish taxonomists: Akai and Arai (1998). However, upon reading the authoritative Fauna Sinica: Osteichthyes - Cypriniformes II by Chen et al. (1998) I realized that R. sinensis is regarded, at least by leading Chinese ichthyologists, as a synonym of R. ocellatus (along with nine other invalid synonyms). As this recent (yet again!) systematics change is likely to be definitive in China, I intend to follow this taxonomic reshuffling on the Rhodeus complex in search of uniformity with the Chinese experts, unless more rigorous DNA analysis suggests otherwise. The systematics of the Family Acheilognathinae is still very confusing though; for example Akai and Arai (1998) regarded R. sinensis as a senior synonym of R. lighti. On the other hand Chen et al. (1998) treated R. sinensis as invalid but recognized R. lighti as a full species. It is thus interesting to note that the body length : body depth ratio remains consistent for my now breeding colony of adult bitterlings collected from Kam Tin, and fits the description of R. sinensis.
Another taxonomic mix-up, albeit unconfirmed, is the new to Hong Kong Channa gachua I included in the same article. It is possible the species is another snakehead instead, C. striata [see also preceding article - Ed.]. Genus Channa is another group of freshwater fish that causes much taxonomic uncertainty. Specimens of the two problematic species will be sent to overseas experts for taxonomic confirmation and I shall report the findings in the near future.
A further mistake of mine in the same article is the listings of locally threatened freshwater fishes. In the mistake - strewn article I listed (only?!) 18 native species as threatened with local extinction which proved to be rather incomplete. I carelessly missed out some 6 species because these species are indeed, so rare that 1 did not recall them until reading my own article in the last a Porcupine!. An obvious example of this group is the pretty stream catfish Pseudobagrus trilineatus found by AFD staff (see Cheung. 1998). For a more complete list of threatened fish please be patient and wait for the multi-author paper on restricted native fauna listing being compiled by Dr Fellowes and Dr. Lau of KFBG. Readers must appreciate two facts: 1) my threatened species listing is a tentative list based on what I have found and also on what other keen ecologists have cared to inform me; 2) there will never be a 'final version' of a threatened species list since the conservation status of any species is subjected to many changing factors.
Finally I would like to announce the overwhelmingly bad response to my 'little message' which called for interested persons to take on our streams. I was wrong in the same article again: pathetically overestimated the interest in more 'non-academic' works (or even just chit-chat) on local streams and other freshwater habitats. I must thank the two kind hearts that read my boring article till the end to notice that message. This time how about a quick tip off of a good lowland stream hidden behind a village somewhere? Won't take you long to drop me an email…..
Akai. Y. and Arai, R. (1998). Rhodeus sinensis, a senior synonym of R. lighti and R. uyekii (Acheilognathinae, Cyprinidae). Ichthyological Research 45(1): 105-110.
Chen, Y. (ed.) (1998). Fauna sinica: Osteichthyes - Cypriniformes II. Beijing: Science Press.
Cheung, K.W. (1998). Two new freshwater fish for Hong Kong. Porcupine! 17: 16-17.
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