The major taxonomic research

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The present report is a compilation of the major taxonomic research works that have been published on the freshwater fishes of Peninsular Malaysia since 1990. We presently record a total of 278 species that are apparently indigenous to the area, as well as an additional 24 now established species that were introduced by man. Since 1990, 45 additional native species and 9 introduced species have been identified and recorded from Peninsular Malaysia. Of the 45 additional native species, 26 were new to science. 22 freshwater fish species are believed to be endemic to Peninsular Malaysia. 14 of these have been scientifically described since 1990. An updated checklist that incorporates the latest developments.

Yet, despite all the discoveries and taxonomic revisions made in the past decade, we are still unable to say that our knowledge of Peninsular Malaysia's freshwater fish fauna is nearly complete. The slew of new fish records in the past decade attests to this deficiency in our knowledge. In reality, we are still in the survey and discovery phase. Most of the area's drainage systems have not been adequately sampled, if at all. New discoveries are still being made and waiting to be published. Lee et al. (1993) provided a database of Peninsular Malaysian freshwater fishes. Kottelat & Whitten (1996) reviewed the status of knowledge on Malaysian freshwater biodiversity. They highlighted the deficiency of a recent publication on the identification of freshwater fish species, but acknowledge the availability of local expertise that can do so.

New species, new records and taxonomic revisions:

Since 1990, 29 species of freshwater fish have been described from Peninsular Malaysia or are subsequently found there (see Appendix I). Some of these taxa were completely new discoveries, being collected during surveys for the first time shortly before the publication of their description. A good example would be the earthworm eel: Bihunichthys monopteroides (see Kottelat & Lim, 1994). This fish appears to have eluded previous collecting efforts as it is small in size and lives mainly in peat swamps - a habitat that had previously been much overlooked by ichthyologists. The loach: Sundoreonectes tiomanensis was an unexpected find in a remote granitic cave on the side of a mountain on Pulau Tioman (Kottelat, 1990a). Its congeners are not found on the mainland, but are instead present on mountains over in Borneo. More recently, two catfishes: Nanobagrus nebulosus and Akysis microps were discovered, and shortly after, described from the Sungai Kahang (Ng & Tan, 1999). A sound knowledge of the fish diversity of the Southeast Asian region, as well as access to a good literature base and well-curated, comprehensive museum collections are criteria that enable any systematic researcher to identify previously undescribed species. Ng (1992b) discusses the main problems affecting systematic research on freshwater fish in Peninsular Malaysia.

Nineteen fish species previously unknown from Peninsular Malaysia have also been documented in the past decade from recent surveys. These new records represent range extensions. The loach: Vaillantella euepiptera was first collected in Peninsular Malaysia during the 1993 survey of Tasik Bera (Lim, 1993). It was previously known only from Borneo. From the black waters of the North Selangor peat swamps, another loach: Kottelatlimia pristes and the two-spotted catfish: Mystus bimaculatus were recorded for Peninsular Malaysia (Ng et al., 1992: 17 as Lepidocephalichthys pristes; Zakaria-Ismail, 1990). Both these species appear to be peat swamp specialists. Kottelatlimia pristes was known originally from Borneo, and Mystus bimaculatus, from Sumatra. From the lower reaches of the Muar and Johor rivers, Kottelat & Lim (1995a) recorded the catfish: Hemibagrus hoevenii and recognized as it as distinct from its congener H. nemurus (now H. bleekeri). Originally described from Java, it is presently also known from Borneo and Sumatra. This is a relatively large fish that is utilized as food by the local people. Another large catfish that went un-noticed by science in the past is Helicophagus waandersii. Recorded from the Pahang River only in the last decade, its discovery in Peninsular Malaysia bridges the gap in its range for the species was otherwise known from Sumatra and Indochina (Lim & Zakaria-Ismail, 1995). The record of the neon goby: Stiphodon atropurpureus on Pulau Tioman in 1997 represents a considerable range extension for the species was known previously from Leyte island in the Philippines (Ng et al., 1999). It is yet to be found elsewhere on the Sunda Shelf.

Some new species and new records were actually first discovered on the shelves of old museum collections. The original specimens of the Chendol eel: Chendol keelini, the glass perch: Parambassis apogonoides and the catfish: Akysis alfredi were collected in the 1960's. The collectors probably did not realize their significance or if they did, did not have the time or resources to work on them. Chendol keelini and Akysis alfredi were described only in the last decade (Kottelat & Lim, 1994; H. H. Ng & Kottelat, 1998b). While Chendol keelini can still be collected today, and is now found to occur outside Peninsular Malaysia, Akysis alfredi has not been seen again. Parambassis apogonoides is reported from Peninsular Malaysia by Roberts (1994b). There is a large series of the goby: Redigobius bikolanus collected from Pulau Tioman in the 1950's at the Raffles Museum in Singapore by Eric Alfred. Although Alfred (1966) made a comprehensive list of Pulau Tioman's freshwater fishes, this common goby was not mentioned, not even misidentified. Ng et al. (1999) are the first to record it from Peninsular Malaysia. The first specimens of the peat swamp snakehead: Channa bankanensis from Peninsular Malaysia were found among collections of fish at the Universiti Malaya in Kuala Lumpur (Ng & Lim, 1991). The Peninsular Malaysian record of the tiger-perch: Datnioides quadrifasciatus was based on specimens collected in the 1930's that are deposited at the California Academy of Sciences in San Francisco, USA (Roberts & Kottelat, 1994 as Coius quadrifasciatus).

Some new fish records have been sourced from popular literature. The first published record of the freshwater stingray: Himantura chaophraya in Peninsular Malaysia came from a Malaysian fishing magazine 'Rod & Line' (Ng & Tan, 1999). A colour photograph of the catch and accompanying locality information enables the identification of this new record. Fishing magazines also contribute information on the abundance of large and endangered game fishes like Probarbus jullieni, Scleropages formosus, Tor tambra, and Leptobarbus hoevenii, as well as rarely seen species like Bagarius yarrelli, Hemibagrus wyckii and Himantura signifer. In addition, they also feature large fish species that have been artificially introduced into Peninsular Malaysia's inland water bodies for aquaculture and recreational purposes. Since 1990, the presence in Peninsular Malaysia of the peacock bass: Cichla monoculus and the Pacu: Colossoma bidens from South America, the catfish: Clarias gariepinus from Africa, and the spotted featherback: Chitala ornata from Thailand were actually revealed in fishing magazines (refer to the monthly issues of 'Rod & Line' from 2000 and 2001).

Some fish species have been regularly collected and identified as known taxa, but their real identities were revealed only when researchers actually conduct systematic revisions on their respective groups. This involves direct comparison with primary type specimens. For example, the catfish: Ompok fumidus described by Tan & Ng (1996) was previously called Ompok leicanthus until an examination of the original Ompok leiacanthus suggests that it is not conspecific with what we had been calling O. leiacanthus in Peninsular Malaysia. Similarly, the eel-loach: Pangio piperata was previously 'passed off' as a colour variant of Pangio muraeniformis until Kottelat & Lim (1993) gave it its current name. Other fish species identified as distinct from their congeners and new to science through systematic revisions in the past decade include the loaches: Schistura robertsi Kottelat (1990b), Pangio alcoides and P. filinaris Kottelat & Lim (1993); the catfishes: Hemibagrus gracilis Ng & Ng (1995), Parakysis longirostris Ng & Lim (1995), Amblyceps foratum Ng & Kottelat (2000), Clarias batu Lim & Ng (1999), Encheloclarias curtisoma and E. kelioides Ng & Lim (1993) and Acrochordonichthys septentrionalis Ng & Ng (2001); and the anabantoids: Betta hipposideros and B. tomi Ng & Kottelat (1994), Betta livida Ng & Kottelat (1992) and Betta pulchra Tan & Tan (1996).

Taxonomic revisions often necessitate the replacement of familiar names with ones that are almost unheard of. Unfortunately, this can be a little confusing when these changes are first implemented. Many of these familiar names were a result of mistakes made by workers in the past. Uncritical acceptance of their work results in the perpetuation of such errors from one generation to the next. Take for instance, the striped barb: Puntius johorensis. Puntius johorensis previously referred to the six-banded barb, presently known as Puntius hexazona. Alfred (1963) thought the type specimen of Barbus tetrazona var. johorensis, being a banded fish, was conspecific with the six-banded barb and started to call it Puntius pentazona johorensis. This is because johorensis is an older name, and in accordance to the Code of Zoological Nomenclature, the older available name should take precedence. Subsequent authors like Kottelat (1989) continued to use that name at the specifc level (i.e. Puntius johorensis instead of Puntius pentazona johorensis). It was recently discovered that the type specimen of Barbus tetrazona var. johorensis is in fact, the juvenile form of the striped barb that was then known to most people as Puntius eugrammus or Puntius fasciatus. The bands on the fish become stripes as it matures, and Barbus tetrazona var. johorensis is conspecific with what was Puntius eugrammus or P. fasciatus. As discussed in Kottelat (1992), P. fasciatus was first used for another species of barb in India, and P. eugrammus is a later name than Barbus tetrazona var. johorensis. Barbus tetrazona var. johorensis therefore becomes the name of the striped barb. The six-banded barb then takes on the next available name that is Puntius hexazona. Rasbora gracilis is a new name given to a common fish that was known previously as Rasbora agilis or Rasbora taeniata. The original type material of R. agilis and R. taeniata are completely different fishes. Therefore, Kottelat (1991a) proposed the new name to avoid perpetuating the mistake further.

Nomenclatural changes also include assignment of species to other genera, some of these revalidated from synonymy, others brand new. The freshwater gobies previously known as Pseudogobiopsis oligactis and P. siamensis are now placed under the revived genus Eugnathogobius (Larson, 2001). The eel-loaches, once more familiarly known in the genus Acanthophthalmus are now placed under an older name, Pangio (see Kottelat & Lim, 1993). The harlequin fish: Rasbora heteromorpha and the catfish: Pelteobagrus ornatus are presently given the new generic names Trigonostigma Kottelat & Witte (1999) and Hyalobagrus Ng & Kottelat, (1998a), respectively. The large, silver barbs that were known as Puntius daruphani or P. pierrei are now placed under the genus Hypsibarbus, recently erected by Rainboth (1996a). See Appendix 1 for a more comprehensive listing.

Finally, taxonomic revisions help to 'tidy up' the masses of names in an area's fauna list. The cyprinid genus Labiobarbus previously had seven names. After Robert's (1993) revision, the names were reduced to four, three having been placed in synonymy. Lim et al. (1993) listed Puntius pierrei and Poropuntius birtwistlei. Now placed in the genus Hypsibarbus, Peninsular Malayisia is found to habour four species of these large barbs after the recent revision by Rainboth (1996a). Other genera that have been systematically revised in the past decade include Osteochilus (Karnasuta, 1993), Pangio (Kottelat & Lim, 1993), Pangasius (Roberts & Vidthayanon, 1991), Parakysis (Ng & Lim, 1995), Acrochordonichthys (Ng & Ng, 2001), Silurichthys (Ng & Ng, 1998), and Betta (Witte & Schmidt, 1992; Tan & Tan, 1996).

Fish communities:

Publications on the diversity of fish fauna in a certain drainage or area are important guides for the formulation of sound conservation strategies. They highlight the presence of rare and/or endemic species, and whether the area is invaded by introduced exotic species. The completeness of the fish species list is very much dependent on how well the drainage is surveyed. The variety of collection methods must be able to record species of all size range and habits. However, due to time, financial, manpower and environmental constraints, it is often difficult to do a thorough survey of any given water body all at once. There have been several publications on the fish diversity in Peninsular Malaysian river basins in the past decade. These compilations were based on literature records and supplemented by original work involving material collected from the field. The most significant of these are herein mentioned:

The North Selangor peat swamp-forest is located along the northern border of Selangor and the southern border of Perak. This area that links the Bernam and Tengi drainages at their lower reaches was surveyed in 1991 and 1992. In spite of the visually unappealing and apparently inhospitable acidic black waters, Ng et al. (1992, 1994) recorded 47 species from there. 14 of these are largely confined to peat swamp habitats. Among these 14 are species previously thought to be rare, but were found to be common there. These include Clarias nieuhofii, Kryptopterus macrocephalus, Mystus bimaculatus, Neohomaloptera johorensis, Puntius johorensis, Rasbora kalochroma and Macrognathus circumcinctus. Also among these 14 are species that were described only in the past decade. They are the fighting fishes: Betta livida and Betta hipposideros, the loach: Lepidocephalichthys tomaculum, and the catfishes: Ompok fumidus and Encheloclarias curtisoma, and the worm-eel: Bihunichthys monopteroides. The loach: Kottelatlimia pristes and the snakehead: Channa bankanensis were new records for Peninsular Malaysia. Parosphromenus harveyi, Betta livida, Betta hipposideros and Encheloclarias curtisoma have not been found outside this patch of peat swamp forest, and are believed to be local endemics. While this area is advocated for conservation as a heritage site, it has been logged and drained for agricultural and industrial development.

Between 1992 and 1993, an extensive ichthyological exploration was carried out by Wetlands International in conjunction with the Malaysian Department of Fisheries and Universiti Malaya on the Pahang basin, the largest drainage in Peninsular Malaysia (Khan et al., 1996). This exploration yielded yet more new records that include the river sprat: Clupeichthys aff. aesarnensis, the barb: Oreichthys sp., the loach: Vaillantella euepiptera, and the catfishes: Ompok euegeniatus and Helicophagus waandersii. The first two are likely to be new to science. There have previously been a number of fish diversity compilations for localized sections of the Pahang basin. These include the Krau Game Reserve (Zakaria-Ismail, 1993), Taman Negara (Zakaria-Ismail, 1984), and Tasik Bera (Mizuno & Furtado, 1982). From specimens deposited in the Raffles Museum from the Tasik Bera survey, a catfish: Akysis alfredi was later described (Ng & Kottelat, 1998).

Ichthyological surveys of the Endau basin, a smaller drainage system located just below the Pahang, were carried out as a part of several expeditions by the Malaysian Nature Society to document the biodiversity of the then proposed Endau-Rompin Park (Zakaria-Ismail, 1987, Lim et al., 1990). Ng & Tan (1999) subsequently made an updated and more comprehensive compilation of the fish fauna of the entire Endau basin that included collections from drainages outside the protected Endau-Rompin Park. In their publication, two new catfishes from the Sungai Kahang: Akysis microps and Nanobagrus nebulosus were described. Another catfish, Hemibagrus gracilis had also been described from the Endau drainage (Ng & Ng, 1995).

Endemic species:

About 22 species of freshwater fish are presently known to occur only in Peninsular Malaysia. 14 of these supposedly endemic species were described only in the last decade. Many of these species have restricted distributions, being found only in certain types of habitats. Endemic species often provide strong justification for the conservation of their indigenous habitats. Similarly, the survival of these species on earth is almost entirely dependent on the proper management and conservation of their environment. Fishes that are specialised to survive in specific habitats are often excellent biological indicators of the health of their respective ecosystems (see Harris, 1995).

Physically isolated habitats like peat swamps appear to display the highest degree of endemism in freshwater fishes. Every peat swamp has its own set of endemic fish fauna especially with regards the air-breathing fishes. The North Selangor peat swamp-forest has Betta livida, Betta hipposideros, Parosphromenus harveyi and Encheloclarias curtisoma. The peat swamps around Kuantan and Pekan that are linked to the Pahang basin has Betta tussyae, Betta waseri and Parosphromenus nagyi. Betta persephone is endemic to peat swamps around Ayer Hitam and Muar in Johor. Betta pulchra is thus far known only from the Pontian area. Betta tomi is restricted to the swamp forests in south-eastern Johor, and Puntius dunckeri apparently shares the same distribution. Both species used also to occur on Singapore island, but are declared extinct there (Ng & Lim, 1996). Unfortunately, peat swamps throughout Peninsular Malaysia are under threat of being reclaimed for agricultural or industrial developments. Puntius dunckeri seems to be commercially bred for the aquarium market. Many species of Betta and Parosphromenus are bred by aquarists in Europe, the United States and Japan. They may not be extirpated if their natural environment is destroyed, but their continued survival in the wild can never be restored if their habitats are not preserved.

Pulau Tioman, an island located in the South China Sea off the east coast of Peninsular Malaysia has at least 14 fish species that live in streams above the tidal reaches (Ng et al., 1999). Despite the relatively low diversity, two species on that island, the loach: Sundoreonectes tiomanensis and the catfish: Clarias batu are not found anywhere else in the world (Kottelat, 1990a; Lim & Ng, 1999). Pulau Tioman has been isolated from the land masses of the Malay Peninsula and Borneo since the last ice age. This is apparently long enough to enable these two species to evolve into forms unique to the island. While Clarias batu is quite common in the streams, Sundoreonectes tiomanensis is known only from a single cave somewhere in the interior of that island. This suggests that it could be the rarest fish species in Peninsular Malaysia at the moment, and any destructive disturbance to its habitat can very easily wipe the entire species out of existence. The carp: Neolissochilus hendersoni could also be an island endemic. For the moment, it is known only from the streams on Penang Island. However, its taxonomic status is not yet satisfactorily resolved. It may prove to be conspecific with Neolissochilus soroides that occurs in the headwaters of drainages throughout the Malay Peninsula.

The remaining endemic species may be more widespread than is presently believed, mainly because their habitats are more extensive. From the Pahang basin, we have Pangio filinaris and Akysis alfredi. From the Endau basin, Nanobagrus nebulosus and Akysis microps. From the Muar basin, Hyalobagrus ornatus. Other endemic species that are found in more than one drainage system throughout Peninsular Malaysia include Rasbora vulgaris, Pangio alcoides and Hemibagrus gracilis. It is possible that these species may be discovered elsewhere in Southeast Asia in the future. As an example, the torrent loach: Homaloptera leonardi was once believed to be endemic to Peninsular Malaysia, but has since been recorded from the Mekong basin (Rainboth, 1996b).

Problems with checklists:

Care has to exercise when comparing different lists of freshwater fishes. The main problem lies with how the term 'freshwater fish' is defined. Mohsin & Ambak (1983: 199-214) listed 375 apparently indigenous freshwater species from Peninsular Malaysia, but 106 of these occur sporadically in freshwater, or are marine forms that are confined to the tidal reaches of inland drainages. Lim et al. (1993) listed 260 native species of freshwater fishes (excluding two which were actually introduced taxa as present knowledge shows), from Peninsular Malaysia. That list was based only on species that apparently complete their entire life cycle in freshwater. The present list of 302 species, however, covers seven additional species that are obligate inhabitants of freshwater throughout their adult lives. These include one eel: Anguilla bicolor, and several gobiids: Eleotris melanosoma, E. oxycephala, Glossogobius giuris, G. aff. celebius, Redigobius bikolanus and Stiphodon atropurpureus.

The area of coverage in the different checklists should always be checked. In Kottelat (1989), the boundaries are geographical, defined by drainage systems or clusters of smaller drainages. His 'Malay Peninsula' (note: not Peninsular Malaysia) also includes Thailand south of the Isthmus of Kra, as well as Singapore. as well as earlier ones by Lim et al. (1993) and Mohsin & Ambak (1983: 199-214) refer to 'Peninsular Malaysia'. The boundaries are thus, political in nature, restricted within Malaysian territory.

In the absence of critical evaluations of the fish diversity in a given area, a single species may be listed more than once under different names. This will create a false impression that the diversity is larger than it really is. It may be due to listing of synonyms, and of names under which a species may have been misidentified. In the checklist of Mohsin & Ambak (1983: 199-214), Wallago attu, Wallagonia leeri and Wallagonia tweediei appear as different taxa. However, Wallago attu is a misidentification of Wallago leeri, while Wallagonia tweediei is a synonym of Wallago leeri (Ng, 1992a). In another example, Channa bistriata is listed alongside C. lucius, but it is a synonym of the latter (Alfred, 1964); and while Channa orientalis is listed along with C. gachua, it is actually a misidentification of the latter. In the checklist of Lim et al. (1993), Tor soro, Neolissochilus hexagonolepis and Neolissochilus soroides refer to Neolissochilus soroides (pers. obs.). This goes to show that the number of species can fluctuate from one checklist to the next. The checklist with the most names may appear impressive on the surface, but it may not necessarily be the most accurate one.

Acknowledgements: We are grateful to Peter Ng for his comments on the manuscript, and to M. Kottelat, H. H. Ng and Mohd. Zakaria-Ismail who generously shared unpublished information on Malaysian fish fauna with us.


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Ng, H. H. & M. Kottelat, 1998b. The catfish genus Akysis Bleeker (Teleostei: Akysidae) in Indochina, with descriptions of six new species. Journal of Natural History. 32: 1057-1097.

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Ng, H. H. & K. K. P. Lim, 1995. A revision of the Southeast Asian catfish genus Parakysis (Teleostei: Akysidae), with descriptions of two new species. Ichthyological Exploration of Freshwaters. 6 (3): 255-266.

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