Hydrobiologia 285: 203-218, 1994.A. Sasekumar, N. Marshall & D. J. Macintosh (eds), Ecology and Conservation of Southeast Asian Marine andFreshwater Environments including Wetlands.© 1994 Kluwer Academic Publishers. Printed in Belgium.

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Diversity and conservation of blackwater fishes in Peninsular Malaysia,particularly in the North Selangor peat swamp forest

Peter K. L. Ng, J. B. Tay & Kelvin K. P. LimDepartment of Zoology, National University of Singapore, Kent Ridge, Singapore 0511,Republic of Singapore

Key words: blackwater fish, Peninsular Malaysia, stenotype, rare taxa, ecology, conservation

Abstract

One of the most extreme freshwater habitats in Peninsular Malaysia is the peat swamp forest, withdark-coloured and highly acidic waters. Surprisingly, little is known about blackwater fishes in Penin-sular Malaysia. Until 1968, only 26 fish species were known from blackwaters throughout PeninsularMalaysia, of which only one can be regarded as stenotopic. A recent intensive survey of part of the NorthSelangor peat swamp forest yielded 47 species, of which 14 are probably stenotopic taxa. These includefour undescribed species and several new records for western Peninsular Malaysia. These discoveriesare significant in that they include the family Chaudhuriidae which until 1985, was not reported fromSundaic Southeast Asia, and the rare genus Encheloclarias which had not been encountered for over 50years. The rapid rate of destruction of the peat swamp forest owing to development, forestry and agri-cultural activities must be halted or slowed significantly to enable the proper zoological surveys andstudies to be conducted. Conservation plans and environmental impact assessments based on inadequatesampling and knowledge of species present is acutely dangerous. There are no longer substantial un-disturbed blackwater peat swamp forests left in most of Peninsular Malaysia. Conservation of the re-maining blackwater biotopes is critically important if extinction of many species, here regarded aseconomically valuable renewable resources, is to be prevented.

Introduction

Peat swamp forests are one of the most threat-ened, yet least studied and most poorly under-stood biotopes in Peninsular Malaysia. One ofthe most extreme peat swamp water habitat iswhat is termed 'blackwaters'. Although Johnson(1967a, b, 1968) recognised several kinds ofblackwaters in Peninsular Malaysia, the most ex-treme in conditions are those which have dark,tea-coloured waters and low pH.

Many of the blackwater peat swamp areas inSingapore and Peninsular Malaysia listed by

Wyatt-Smith (1959, 1964), Johnson (1967a,1968), Anderson (1983) and Whitmore (1984,1988) have been converted to padi, pineapple oroil palm plantations, or developed for some otheruse. The blackwater swamp forests in Johor, pre-viously the most extensive in Peninsular Malay-sia, are nearly gone. What remains of the black-water peat swamps of any substantial size inPeninsular Malaysia appear to be restricted tonorthern Selangor, central Terengganu and partsof Pahang. In Johor, only pockets of the old peatswamps remain. There is thus at present, anurgent need to conduct more studies on the

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remaining blackwater peat swamp forests beforethey are also lost through reclamation for agri-cultural development.

The freshwater fishes that inhabit blackwatersare poorly known. There have been few directstudies on blackwater species. Studies on acidblackwater fishes were made by Johnson (1967b,1968), who compared species composition withthat of other freshwater habitats. He (1968) com-mented that blackwaters were generally species-poor in fishes. Even less is mentioned in the re-cent book on Malaysian fishes by Mohsin &Ambak (1983). Mizuno & Furtado (1982) re-ported on an extensive ecological study of fishesin the swamp-lake of Tasik Bera in Pahang, whichincludes peat swamp forests with blackwaters (seealso Lim et al., 1982; Shiraishi et al., 1972) butdid not specify which species actually line inblackwaters (see discussion later). In recent years,several anabantoids have been described from ornear Malaysian blackwaters by aquarists - Bettatussyae Schaller, 1985, Betta waseri Krummen-acher, 1986, Betta persephone Schaller, 1986,Parosphromenus nagyi Schaller, 1985, and Paros-phromenus harveyi Brown, 1987. Several newrecords have also been reported. Vierke (1988)mentioned Betta coccina from near acid watersnear Batu Arang, Rawang, while Zakaria-Ismail(1991) and Ng & Lim (1991) recorded Mystusbimaculatus (Bagridae) and Channa bankanensis(Channidae), respectively, from or near blackwa-ters of the North Selangor peat swamp forest.

There has only been one concerted effort inMalaysia in recent years to study blackwater spe-cies, and that is the survey by Davies & Abdullah(1989) of the North Selangor peat swamp forest.They obtained 16 species from blackwater sites.In four repeated surveys of the same forest overa period of 12 months, the authors obtained 47blackwater species, the highest number of black-water taxa recorded so far from Peninsular Ma-laysia.

Considering that the fish fauna of PeninsularMalaysia is relatively well studied compared toneighbouring areas, this lapsus in sampling andknowledge is surprising. This might well be due tothe extreme dark colour, low dissolved oxygen

level and high acidity of blackwaters, which mayhave given rise to the misconception that suchbiotopes are 'inhospitable', and thus sustain apoor faunal diversity. The results of Johnson(1967a, b, 1968) show the presence of only 26species in blackwaters, of which only one is astenotopic blackwater taxon.

Here, we review what is known about black-water fishes in Peninsular Malaysia, and elabo-rate on the importance of this knowledge for fishconservation. The possible reasons for previousstudies having underestimated the fish diversityand resource are discussed. We draw mainly fromour experiences with the North Selangor peatswamp forest (Fig. 1) and the remaining patchesin Johor.

The chemistry and definition of blackwaters

Johnson (1967a, b, 1968) defined blackwater aswaters originating from peat swamp forests,highly acidic with pH ranging from 3.6 to 5.9,tea-coloured when seen against transmitted light,and black when seen en masse via reflected light.Johnson (1967b) recognised three types of black-waters: Gelam (i.e. Melaleuca-associated), diluteand polluted. The blackwaters discussed in thepresent study generally follow Johnson's (1967a,1968) chemical definition, but the type is not oneof the three he recognised. A fourth type shouldbe recognised - concentrated blackwaters. Thisis the habitat on which many of our studies havebeen based.

Johnson (1967a, 1968) noted that blackwatersin Peninsular Malaysia are rich in sulphate ascompared to those in Amazonia, which are richin chloride (see also Junk & Furch, 1985). It is thepresence of high concentrations of sulphates thatprobably accounts for the very low pH. Peat de-rived from plant detritus is found at blackwatersites and is usually about 0.5 metres thick (seeWhitmore, 1984, 1988).

There have been no detailed limnological stud-ies on blackwaters since Johnson's papers, al-though the work of Lim et al. (1982) for TasikBera (which includes peat swamps) should be

o 20 40 6 80 100km

Fig. 1. Map of Peninsular Malaysia, showing the North Selangor peat swamp forest (blackened area).

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'N

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consulted. Johnson's work was based primarilyon the blackwater swamp forests of southern Ma-laysia (mainly Johor). Although the physico-chemical characteristics of the blackwaters in theswamps of north Selangor (being on the westcoast) are probably very similar to those of Johor,no detailed studies have been done to validatethis. Soil conditions on the east coasts of Malay-sia are different, and some differences in thephysico-chemical characteristics of the blackwa-ters can be expected, e.g. those from Terengganu.

Classification of fish habitat preferences

The division between blackwaters and usual for-est acid waters (fide Johnson, 1967a) is not al-ways clear, and both often gradually blend intoeach other. There has been no proper study of thelimnological and physico-chemical aspects of thisdemarcation. Johnson (1967a, b) for example,recognises 'dilute blackwaters' which are brown-coloured and higher in pH. Brown-tinted acidwaters are still common in many parts of Malay-sia, even in plantations. Many acid water speciesseem quite capable of coping with blackwaters. Inthe present study, three tentative categories ofspecies are recognised - eurytopic, stenotopicacid water, and stenotopic acid blackwater. Eu-rytopic species are those which are often commonand thrive in slightly acidic to neutral waters oreven slightly alkaline, as well as acid waters, beingable to thrive in open-country as well as forest-country habitats (fide Johnson, 1967b, 1973).Stenotopic acid water species are usually three-country species, and occur only in acidic waters(pH usually less than 6), although many are prob-ably also able to thrive in blackwaters. Stenotopicacid blackwater species are those that appear tobe confined to the high acidity, dark-colouredblackwaters, usually in or adjacent to forest-country habitats.

We emphasise that this categorisation is ten-tative. It is possible that the taxa classified hereas stenotopic blackwater species might perhapsbe stenotopic to a special food item in blackwa-ters, a particular substrate present etc., and not

necessarily by pH alone. Categorisation of thevarious species is based partly on the scarce pub-lished literature and more on our collecting expe-riences with these fishes.

Habitat preferences of some species, especiallythe rarer or newly discovered ones, are probablynot very accurate. Some species however, nota-bly Channa bankanensis, appear to be strict,stenotopic acid blackwater taxon. We obtainedlarge numbers of this species from Selangor andJohor, but only from blackwaters; it is not knownin the nearby peripheral habitats. Species such asSphaerichthys osphromenoides, have been found inMalaysian acid water habitats that are not strictlyblackwaters. They seem to grow to much largersizes, and have the largest populations in black-waters. This is true not only in the North Se-langor peat swamps but also in Johor. Also,Sphaerichthys osphromenoides has been collectedpredominantly (if not entirely) from blackwaterhabitats in Borneo (see later; M. Kottelat, pers.comm.) Betta livida, and Parosphromenus harveyiare rare in the acid waters of the Rawang area(where the swamp forests have been severely dis-turned and destroyed), and extremely abundantin blackwaters. We prefer to classify these threespecies as stenotopic acid blackwater taxa. Manyauthors also closely associate Luciocephalus pul-cher with highly acidic blackwater streams andswamps. While it is true that they are quite com-mon in blackwaters, substantial populations andlarge breeding individuals also occur frequentlyoutside blackwaters in forested acid water habi-tats (fide Johnson, 1967a; pers. obs.).

The present categorisation tentative though itis, permits approximate comparisons and usefuldiscussions to be made of Malaysian blackwaterfishes, especially with regards to the stenotopicacid blackwater fauna.

Blackwaterfishes in Peninsular Malaysia

Other than the papers by Johnson (1967b, 1968)and Davies & Abdullah (1989) who dealt withblackwater fishes from Johor and Selangor re-spectively, there have been no other papers whichemphasise the blackwater fauna. Of the 47 spe-

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cies recorded at present from the North Selangorswamp forest, Moshin & Ambak (1983) listed 38species although many of the species were notcollected by them. They collected only one of thestenotopic blackwater species (Sphaerichthys os-phromenoides); most of the other species wereclassified as 'rare or extinct'. Of interest is thePuchong site in Selangor sampled by Moshin &Ambak (1983) where they obtained Sphaerichthysosphromenoides and Parosphromenus deissneri(Bleeker, 1859). This area is a disturbed swampforest, a remnant of larger swamps that werepresent in the area (S. Lim, pers. comm.).

The information on the peat swamp fish diver-sity of Terengganu is based primarily on the col-lections of Tweedie (1952) from the Merchangand Kuala Brang areas. He noted that the habi-tat had acidic blackwaters and he described theblackwater Parosphromenus paludicola, and re-corded Rasbora kalochroma. Seven acid waterspecies were also listed Luciocephalus pulcher,Puntius hexazona, Rasbora cephalotaenia, R.pauciperforata, R. gracilis, R. dorsiocellata, Nandusnebulosus and Kryptopterus macrocephalus. WeeB. T. (unpublished data) regarded Parosph-romenus paludicola (incorrectly as P. deissneri) asan acid water species in her survey of the Tereng-ganu waters and swamps. Aquatic life of largepeat swamp forests in central Terengganu is,however, still poorly explored.

The important study by Mizuno & Furtado(1982) on Tasik Bera in Pahang was based mostlyaround the more accessible area around Fort Is-kandar. Lim etal. (1982: 10) noted that abouttwo-thirds of Tasik Bera (ca 67%) was swampforest with peat substrate; and three habitat typescould be distinguished in the study site: Utricu-laria stands, Lepironia stands, and open waterareas. Although blackwaters were reported aspresent, the extent of the survey on this habitatwas not specified. The presence of large numbersof submerged macrophytes in the study area (seeMizumo & Furtado, 1982) suggests that the studyarea had mainly dilute blackwater. Mizuno &Furtado (1982) did not indicate which specieswere collected from blackwaters. They comparedtheir species with those of Johnson (1967b) and

noted that 11 species could be classified under his'dilute blackwaters habitat' category. Of the 95species reported from Tasik Bera by Mizuno &Furtado (1982), only two, Sphaerichthys osph-romenoides and Ompok leiacanthus, can be re-garded as stenotopic acid blackwater species.There were true blackwater areas in the area butthese were not sampled or fully explored, andmost of the sampling had been done in tree-country acid water habitats with pale tea-colouredwaters (R. P. Lim, pers. comm.).

The extensive freshwater peat swamps aroundKuantan, Pahang, have been poorly explored. Therecent discoveries of acid blackwater species frompeat swamps in Pahang (Betta tussyae, Bettawaseri, Parosphromenus nagyi) (Schaller, 1985a, b;Krummenacher, 1986) reflect this neglect. In arecent survey of the swamps around Kuantan, wehave also obtained other stenotopic acid black-water species not previously known from theswamps there: Channa bankanensis, Sphaerichthysosphromenoides and Macrognathus circumcinctus.Surveys of the blackwater fish fauna in south-western Johor have also revealed several newspecies and records (see Schaller, 1986; Lee &Ng, in press).

Studies on the fish fauna of Taman Negara andEndau-Rompin, have included little mention offishes from blackwaters (see Zakaria-Ismail,1984, 1987; Lim et al., 1990a, b). In his studies ofthe Malaysian freshwater fishes, Zakaria-Ismail(unpublished data) observed that some of the fewendemic Malaysian species (Parosphromenusnagyi, Parosphromenus paludicola) were confinedto the blackwater habitat, and that the absence ofspecies like Sphaerichthys osphromenoides, Lucio-cephalus pulcher and Parosphromenus deissneri inThailand and Indo-China is correlated with ab-sence of blackwater swamps there. Parosph-romenuspaludicola has since been found in south-ern Thailand (see Kottelat, 1989).

The blackwater ichthyofauna of Sundaic SoutheastAsia

The Sarawak ichthyofauna as a whole is ratherpoorly sampled, although the blackwater fish

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fauna there is probably diverse. Possible black-water species include Ompok leiacanthus (seeRoberts, 1989: 151), Betta livida and Parosph-romenus allani Brown, 1987. Rasbora kalochromaand an unidentified Sphaerichthys have also beenrecorded (Brown & Brown, 1987). The freshwa-ter fish fauna of Sabah is well studied, but al-though there are blackwater areas there (P. K.Chin, pers. comm.), no specific reference havebeen made to such habitats (see Inger & Chin,1962, 1990). In fact, the colour of the water andpH were not mentioned in their habitat descrip-tions; and only nine species were obtained thatare here recognised as stenotopic acid water taxa.Interestingly, no acid water anabantoids (Belon-tiidae), so prominent in Malaysian blackwaters,were collected. Proper surveys of the Sabahanblackwater habitats have yet to be made (P. K.Chin, pers. comm.).

The important study by Roberts (1989) did notconcentrate on blackwater habitats. He did notspecifically mention blackwaters; although helisted many areas as having brown or brown-tinted water. Only in two of his collecting sites(1976-4 and 1976-5, Roberts, 1989: 13) were thewaters acidic enough (pH 4.5-5), to possibly beacidic blackwaters. In one site (1976-5) he notedthe waters as appearing black when viewed fromabove. Other than these two sites, the other acidwater sites had pH values from 5.5 to 6.5. In thetwo pH sites however, Roberts collected all hisspecimens of Sphaerichthys osphromenoides, Pa-rosphromenus parvulus (=P. ornaticauda), hissingle specimen of Neohomaloptera johorensis,most of his specimens of Puntius rhomboocellatusKoumans, 1950, and all his specimens of Rasboraaxelrodi Brittan, 1976 (= R. kalbarensis Kottelat,1991). Roberts (in litt.) commented that he hadtried to reach good blackwater habitats in thelower Kapuas but those which were accessiblewere mainly spoiled by canals. In a follow-upstudy by Kottelat in the same area, which in-cluded the sampling of blackwaters, Ompok lei-acanthus, Betta rutilans Witte & Kottelat, 1991,Parosphromenus ornaticauda Kottelat, 1991, andNagaichthys filipes Kottelat & Lim, 1991, werefound (Kottelat, 1991; M. Kottelat, pers. comm.).

Many anabantoids have also been reported fromacid blackwaters in Borneo: Sphaerichthys sela-tanensis Vierke, 1979, Betta anabatoides, Bleeker,1850, Bettafoerschi Vierke, 1979, Parosphromenus

parvulus Vierke, 1979, Parosphromenus filamento-sus Vierke, 1981, and Parosphromenus ornaticauda(see Kottelat, 1991; Linke, 1990).

The blackwater swamps of Sumatra are exten-sive but poorly studied. Many species have beendescribed or reported which are here recognisedas acid blackwater species, although this is rarelymentioned, e.g. Channa bankanensis (Ng & Lim,1990), Mystus bimaculatus (see Zakaria-Ismail,1990), Rasbora kalochroma (Brittan, 1954b), andBetta coccina Vierke, 1979 (see Linke, 1990).

There have been almost no studies of black-water areas in southern Thailand. Some of thestenotopic acid water and blackwater speciescould conceivably be there.

A case study: the North Selangor peat swampforest

Our study sites in the North Selangor peat swampforest (Fig. 1) were blackwater streams andditches along the trunk road between KampungSungai Besar and Tanjung Malim. The vegeta-tion is rather dense with Macaranga and Panda-nus spp. being dominant. Water depth rangedfrom about 30 to 160 cm, in tandem with thefluctuating rainfall. The pH of the water is verylow, ranging from 3.4 to 3.8. This pH level issignificantly lower than that reported by Johnson(1967a, 1968) for most blackwaters, but appearsto be usual for the North Selangor swamp forest.Colour of the water varied from a dark tea- tocoffee-coloured. The substrate of the streams areusually composed of a layer of peat and wooddebris of varying thickness.

The North Selangor peat swamp forest waspreviously more extensive than it is now, extend-ing into parts of the Rawang area in the south.Development has sharply reduced the total areacovered. For further details on the swamp forest,see Chan (1989), Low & Balamurugan (1989) andPrentice (1990).

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A note on the material collected Table 1. List of fishes collected from blackwater streams inthe North Selangor Peat Swamp Fore

The present study by the National University ofSingapore of the North Selangor peat swamp sur-vey covered a time-frame of 12 months (May1991-June 1992), with eight sampling periods.This time-frame included periods of high water(May) as well as lowest water (August). Thespecimens obtained are still under study, and sev-eral reports describing the new species of fish,other aquatic vertebrates and some invertebrates,discussing the diversity and ecology of the speciesare in preparation. Reference specimens havebeen deposited in the Institute of Advanced Stud-ies (University of Malaya); Department of Zool-ogy, University of Malaya; and the ZoologicalReference Collection of the National Universityof Singapore. Readings of pH were made withelectronic pH meters, and the glass electrodeswere standardised with buffers before each set ofreadings. Approximate corroborative readingswere obtained with universal pH paper.

Some taxonomic comments

Forty-seven freshwater fish species, representing18 families, were obtained from blackwaterstreams in the present series of investigation inthe North Selangor Peat Swamp Forest (Table 1).

There had been an unfortunate confusion in theidentities of the cyprinids known as the Six-banded and Striped Barbs, presently known asPuntius johorensis Dunker, 1904, and P. eugram-mus Silas, 1956, respectively. Kottelat (1992)showed that the type of P. johorensis is actuallyidentical with the species now known as P. eu-grammus, and as P. johorensis is an earlier name,it has priority over P. eugrammus. This is unfor-tunate as Puntius eugrammus had been a replace-ment name for P. fasciatus (which the Malayanfishes had been called for a long period), a namealready preoccupied for an Indian species (seeRoberts, 1989). That means the name of the Six-banded Barb, presently incorrectly known as'P. johorensis', should be called P. hexazonaWeber & de Beaufort, 1922, instead. Puntius

E - eurytopic (acid to neutral or slightly alkaline)S - stenotopic to acid blackwatersA - stenotopic to acid waters

Family CYPRINIDAE1. Osteochilus spilurus (Bleeker, 1851) A2. Puntius johorensis Duncker, 1904 A3. Puntius hexazona Weber & de Beaufort, 1922 A4. Rasbora cephalotaenia (Bleeker, 1852) A5. rasbora dorsiocellata Duncker, 1904 A6. rasbora einthovenii (Bleeker, 1851) A7. Rasbora gracilis Kottelat, 1991 A8. Rasbora kalochroma (Bleeker, 1851) S9. Rasbora maculata Duncker, 1904 A

10. Rasbora pauciperforata Weber & de Beaufort, A1916

Family BALITORIDAE11. Neochornaloptera johorensis (Herre, 1944)

Family COBITIDAE12. Lepidocephalichthys tomaculum Kottelat & Lim,

199213. Lepidocephalichthys pristes Roberts, 1989

Family BAGRIDAE14. Leiocassis micropogon (Bleeker, 1852)15. Mystus bimaculatus Volz, 190416. Mystus nemurus (Valenciennes, 1839)

Family PARAKYSIDAE17. Parakysis verrucosa Herre, 1940

Family SILURIDAE18. Kryptopterus macrocephalus (Bleeker, 1858)19. Ompok leiacanthus (Bleeker, 1853)20. Silurichthys hasseltii Bleeker, 1858

Family CLARIIDAE21. Clarias meladerma Bleeker, 184722. Clarias cf. nieuhofii Valenciennes, 184023. Clarias teijsmanni Bleeker, 185724. Encheloclarias curtisoma, Ng & Lim, 1993

S

A

A

ASE

A

AS (A?)A

EAAS

Family HEMIRAMPHIDAE25. Hemirhamphodon pogonognathus (Bleeker, 1853) A

Family SYNBRANCHIDAE26. Monopterus albus (Zuiew, 1793) E

Family CHAUDHURIIDAE27. New genus, new species S

Family MASTACEMBELIDAE28. Macrognthus circumcinctus (Hora, 1924) S (A?)

Family PRISTOLEPIDAE29. Pristolepis grootii (Bleeker, 1876) A

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Table 1. (Continued)

Family NANDIDAE30. Nandus nebulosus (Gray, 1835)

Family ANABANTIDAE31. Anabas testudineus (Bloch, 1792)

Family BELONTIIDAE32. Belontia hasselti (Cuvier, 1831)33. Betta bellica Sauvage, 188434. Betta livida Ng & Kottelat, 199235. Betta, new species36. Parosphromenus harveyi Brown, 198737. Sphaerichthys osphromenoides Canestrini, 186038. Trichogaster leerii (Bleeker, 1852)39. Trichogaster pectoralis (Regan, 1910)40. Trichogaster trichopterus (Pallas, 1770)41. TRichopsis vittata (Cuvier, 1831)

Family HELOSTOMATIDAE42. Helostoma temminckii Cuvier, 1831

Family LUCIOCEPHALIDAE43. Luciocephalus pulcher (Gray, 1830)

Family CHANNIDAE44. Channa bankanensis (Bleeker, 1852)45. Channa gachua Hamilton, 182246. Channa lucius (Cuvier, 1831)47. Channa melasoma (Bleeker, 1851)

A

E

A (S?)ASSSSA (S?)EEE

A

A

SAAA

hexazona had been previously regarded as ajuniorsynonym of 'P. johorensis'.

Four species have been identified as new. Theyare one new cobitid loach of the genus Lepi-docephalichthys Bleeker, 1863 (L. tomaculum)(Kottelat & Lim, 1992), an undescribed genusand species of chaudhuriid eel (Kottelat & Lim,in prep.), a clariid catfish of the genus Enchelo-clarias Herre & Myers, 1937 (see Ng & Lim,1993), and a new species of Betta (B. livida) (Ng& Kottelat, 1992). The family Chaudhuriidae isrecorded for the first time from Selangor, and thefamily, until 1985, was not known from SundaicSoutheast Asia (see Kottelat, 1985; Kottelat &Lim, in Kottelat, 1991). The genus Encheloclariasin Peninsular Malaysia, was previously knownfrom a single specimen (identified as E. tapeinop-terus (Bleeker, 1852) collected from southeasternJohor. The genus Encheloclarias, until the presentsurvey, was believed to be monotypic. The speci-

mens from Sambas, Banka and Johor reportedupon by Bleeker (1858, 1862) and Herre & Myers(respectively) are not conspecific (Ng & Lim,1993). Lepidocephalichthys pristes Roberts, 1989,known previously only from western Kalimantan(Roberts, 1989), Kalimantan Tengah, Kaliman-tan Timur and Sarawak (M. Kottelat, pers.comm.), is now reported from Peninsular Malay-sia. Betta, new species, belongs to a species-groupknown previously from Pahang and Sumatra(Krummenacher, 1986; Kottelat & Whitten, 1993;Ng & Kottelat, in press). The present specimensdiffer from B. waseri s. str. in head shape andmarkings. The blackwater balitorid loach, Neo-homalopterajohorensis and akysid catfish Paraky-sis verrucosa has not been previously recorded asfar north (see Alfred, 1969; Roberts, 1989).Rasbora kalochroma, previously known from onlya few specimens from Johor and Terengganu(Brittan, 1954a; Tweedie, 1952; Zakaria-Ismail,1987), is now reported from northern Selangor.The range of Macrognathus circumcinctus, previ-ously known only from Terengganu and Kelantan(Sufi, 1956; Cramphorn, 1983; Zakaria-Ismail,unpublished data), is also extended to the westcoast of Peninsular Malaysia.

The identity of the poorly described Parosph-romenus harveyi (fide Brown, 1987) has causedsome taxonomic problems in that the original de-scription was far too brief and imprecise, with notype designations, indication of number of speci-mens examined or site of specimen deposition.Although P. harveyi is similar to P. nagyi, both arecertainly valid species, despite the poor originaldescriptions of both taxa. We have obtainedtopotypic material of P. harveyi from near BatuArang, near Rawang, Selangor, and it agrees withthe excellent series we now have from northernSelangor. Topotypic specimens of P. nagyi havealso been obtained and compared directly withP. harveyi. Parosphromenus harveyi, differs fromP. nagyi distinctly in colour patterns and length ofthe pelvic fin (shorter in P. nagyi) (see alsoSchaller, 1985a; Linke, 1990). Redescriptions ofP. nagyi and P. harveyi are being prepared.

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Discussion

Diversity of Malaysian blackwater ichthyofauna

Of the 47 species recorded from the North Se-langor blackwater peat swamp, nine are consid-ered to be eurytopic, 25 stenotopic acid water and13 stenotopic acid blackwater taxa. The speciesrecognised as stenotopic acid blackwater taxa areNeohomaloptera johorensis, Rasbora kalochroma,Channa bankanensis, Sphaerichthys osph-romenoides, Betta aff. waseri, Betta livida, Parosph-romenus harveyi, Encheloclarias, new species,Ompok leiacanthus, Mystus bimaculatus, newgenus and species of chaudhuriid and Macrog-nathus circumcinctus.

Our list contrasts strongly with Johnson's(1968) report that Malaysian blackwaters seem tobe especially depauperate in fish species. Johnson(1967b, 1968) commented that he had collectedonly 26 species (only a partial list of species pro-vided) from blackwaters in Malaysia, of whichonly 15 are frequently found. Of these, onlySphaerichthys osphromenoides is a stenotopic acidblackwater species. Of the 15 'blackwaterfrequents', he regarded three as typical of morepolluted blackwaters: Trichogaster trichopterus,Channa striata and Dermogenys pusillus. Threewere associated with gelam blackwaters (Anabastestudineus, Betta imbellis (as B. splendens) andRasbora maculata), eight from typical blackwaters(Puntius hexazona (as P. pentazona), Puntius jo-horensis (as P. lineatus), Rasbora pauciperforata,Rasbora cephalotaenia, Hemirhamphodon pogo-noganthus, Sphaerichthys osphromenoides, Betta cf.pugnax (as B. picta) and Channa lucius (as anOphicephalus). Only one was common in mostkinds of blackwater, Rasbora einthovenii.

Davies & Abdullah (1989) recorded 16 species(in six families) from the blackwaters of the NorthSelangor swamp forest, using mainly cast nets,gill nets and baited lines. Not surprisingly, onlylarger species were collected. Of their 16 species,only three were stenotopic acid blackwater taxa.In our surveys fishes as small and hair-like as thenew genus and species of chaudhuriid eel werecollected. The differences observed can be attrib-

uted mainly to two factors - collecting methodsand time of collection.

Our collecting gear, rectangular hand-held pushnets measuring 60 by 45 cm with fine mesh, isespecially effective in the blackwaters as it ishighly portable, can be operated by one personand will work even in shallow or narrow streams.Two-man teams however, are usually employed,with one holding the net and the other disturbingthe submerged vegetation, mud and detritus todrive the animals into the net. The same spot maybe sampled several times, even after a short in-terval. The disturbed substrate tends to uncoversmall organisms, thus attracting predatory spe-cies (e.g. Silurichthys, Clarias, Mystus, Macrog-nathus and Channa). Choice of mesh size is criti-cal. We used mesh size of about 5 mm, and eventhen, this was barely small enough to capturespecies such as the new genus and species ofchaudhuriid eel.

The cast net proved difficult to use for tworeasons. First, the mesh size is too large to trapsmall pelagic species such as Rasbora maculata orR. gracilis. Second, the dark water tends to con-ceal the presence of submerged branches. Netsthat become entangled with these objects are oftenvery difficult to extricate. The same is true for grillnets. Electrofishing was not attempted as thestunned fish that sink to the bottom are difficultto recover due to the dark colour of the water.Fishing with hook and line is effective, but tendsto sample only the larger predatory species e.g.Channa or Clarias. Local fishermen use wickertraps baited with oil palm nuts. Large speciessuch as Belontia, Pristolepis and Clarias were ob-served in such traps. Use of these traps will prob-ably be very effective for larger species, especiallyif the traps are properly baited with strong-smelling food. The collecting methods used in oursurveys differ from those used by earlier workers(see Johnson, 1967b; Davies & Abdullah, 1989)in that they are more 'active' than 'passive'.

As most of the water input in the swamp for-est is by precipitation, the amount of rainfall thuslargely determines the water level in the streams.The level of water in the streams in August 1991was found to be about half that measured in June

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the same year. Some fish species that were abun-dant in June were caught in smaller numbers inAugust, e.g. Clarias spp., Rasbora kalochroma,Ompok leiacanthus and Betta livida. On the otherhand, some species, such as Lepidocephalichthyspristes, uncommon in June, were very abundant inAugust and September. The same appears to betrue of Parosphromenus harveyi, with many of theAugust/September males in full breeding colou-ration, suggesting that there is probably a higherincidence of breeding in this and probably otherspecies during low water. Lepidocephalichthyspristes not only becomes abundant in August, itattains larger sizes. Our studies thus show that aparticular species recorded as 'rare' at a particu-lar time, may be abundant at other times.

The high species diversity in the blackwaters ofthe North Selangor swamps should not be sur-prising. Even in the Amazon, a much more in-tensely studied system, blackwaters (e.g. the hugeblackwater river Rio Negro) have species-diver-sities comparable to that in clearer waters (Goul-ding, 1985). Johnson (1967b) noted that theblackwater fish fauna he obtained representedonly 10 % of the total Peninsular Malaysian fauna.About 260 species of primary freshwater fishesare known from Peninsular Malaysia at present(fide Moshin & Ambak, 1983; Kottelat, 1989;Zakaria-Ismail and authors, unpublished data),and the 47 species we have obtained represents18% of the total known ichthyofauna. This ishigher than believed previously, and consideringthe small area we have sampled, this high per-centage is even more significant.

Many known Malaysian species previously re-garded as rare or very rare, such as Rasborakalochroma, Neohomaloptera johorensis, Ompokleiacanthus, Sphaerichthys osphromenoides andMacrognatus circumcinctus were collected in largenumbers in the North Selangor peat swamp for-est. It is obvious that the apparent rarity is due toimperfect sampling of their preferred habitat, i.e.blackwaters. The same is true for known specieslike Channa bankanensis, Mystus bimaculatus,Clarias aff. nieuhofii. Species previously obtainedby aquarists in small numbers from drainageditches are also present in large numbers in the

actual swamp forests (e.g. Betta bellica, Betta, newspecies waseri, Betta livida, and Parosphromenusharveyi), suggesting that type localities of some ofthese species are not the primary habitat. LikeVierke (1987, 1988), we obtained B. bellica fromdark-coloured acid ditch waters in disturbed for-ests near Ayer Hitam, but in North Selangor thespecies is much more common and the specimensobtained are generally larger in size, suggestingthat its preferred habitat is blackwaters.

A significant proportion of the blackwater spe-cies are anabantoids. Thirteen species, of whichfour are eurytopic, five are acid water stenotopicand four are blackwater stenotopic. The belonti-ids are the best represented, with 10 species, i.e.23% of the total blackwater ichthyofauna.Johnson (1967b) had noticed the same trends inhis studies; of the 15 blackwater species he con-sidered important, nine (60 %) were air breathersor lived near the water surface. Our results aresimilar. For the 47 fishes obtained in the presentstudy, 31 species are air breathers (22) or oftenswim near the surface (9). This represents some66% of the total fauna. The ability to breatheatmospheric air is clearly an asset in the extremeblackwater habitat.

Fish biomass in Malaysian blackwaters

Johnson (1968) suggested that blackwaters havea very low productivity, not exceeding five poundsper acre (equivalent to 5.6 kg per hectare). This heattributed partly to the absence of primary pro-duction (e.g. by aquatic macrophytes and phy-toplankton) because of the forest cover and dark-coloured acidic waters. Johnson did not state howthis figure was obtained but he was probably re-ferring to standing stock or biomass, not produc-tivity which has a temporal parameter. Whittenet al. (1987) in their review of Sumatran black-water aquatic life, agreed with most of Johnson'sfindings. The allochthonous nutrient input intoblackwaters, though recognised by Johnson, isprobably much more important. Junk & Furch(1985) commented that the great number of fishrecorded from Amazonian blackwaters was pre-

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dominantly due to allochthonous inputs - insects,fruits, pollen etc.

An intensive and thorough collection was madeat one North Selangor site which covered about50 square metres. The fish field, comprisingmainly of the snakehead, Channa bankanensis,and the spiny eel, Macrognathus circumcinctus,both edible species, totalled about 0.2 kg. Thisquantity, equivalent to 40 kg per hectare, is a con-servative estimate as smaller species (e.g. Mystusbimaculatus, Betta, new species etc.) were notconsidered. Nonetheless, this figure is still con-siderably higher than that reported by Johnson(1968). The fish biomass of blackwaters isprobably less than large clear water drainages.Bishop (1973) reported a value of some 180 kgper hectare for the Sungei Gombak river systemin Selangor.

Economic significance of the blackwaterichthyofauna

Blackwater peat swamps have been recognised asimportant catchment areas. The thick peat layerstend to absorb and store large quantities of waterin the rains, and this water can be tapped foragricultural use. In North Selangor, the rice fieldsare irrigated by water channeled from the peatswamps (Low & Balamurugan, 1989) as well asfrom the Sungai Bernam via the Karang River.

The economic importance of the ichthyofaunain Peninsular Malaysian blackwater peat swampsshould not be overlooked or underestimated. Al-though blackwater swamps are threatened habi-tats, there is no reason, with foresight and propermanagement, why the rich fish resources therecannot be exploited for consumption and theaquarium trade for the benefit of the local popu-lace.

Harvesting of the larger species for consump-tion, albeit in a small scale by the local peoplehave been observed. The 18 species caught forthis purpose are listed in Table 2. Most of thespecies are sold for very low prices and have onlylocal importance. None of the species is trans-ported far for sale.

Table 2. List of North Selangor blackwater peat swamp fishescollected for consumption by local people and of aquariumimportance.

Food species Aquarium/ornamental species

Mystus nemurus Rasbora cephalotaenia

Mystus bimaculatus Rasbora dorsiocellataKryptopterus macrocephalus Rasbora einthovenii

Clarias teijsmanni Rasbora gracilis

Clarias cf. nieuhofii Rasbora kalichromaClarias meladerma Rasbora maculata

Pristolepis grootii Rasbora pauciperforata

Ananbas testudineus Puntius johorensisBelontia hasselti Puntius hxazona

Trichogaster leerii Osteochilus spilurusTrichogaster pectoralis Hemirhamphodon pogonognathus

Trichogaster trichopterus Mystus bimaculatusHelostoma temminckii Leiocassis micropogon

Macrognathus circumcinctus Krvptopterus macrocephalus

Monopterus albus Silurichthys hasseltii

Channa bankanensis Macrognathus circumcinctusChanna lucius Belontia hasselti

Channa melasoma Betta lividaBetta bellicaBetta, new speciesParosphromenus harveyi

Sphaerichthys osphromenoidesTrichogaster leeriiTrichogaster trichopterusHelostoma temminckii

Luciocephalus pulcher

Channa gachua

The potential for the aquarium trade is verypromising. Among the 47 species collected in thepresent survey, 27 are already or having very goodpotential to be exploited for the aquarium trade(see Table 2). Well known and popular blackwa-ter fishes already established in the trade includethe 'Pearl Gouramy' (Trichogaster leerii), 'Choco-late Gouramy' (Sphaerichthys osphromenoides),'Clown Rasbora' (Rasbora kalochroma), 'Six-Banded Barb' (Puntius hexazona), and the 'Two-spot Catfish' (Mystus bimaculatus). With the gen-eral popularity of anabantoids, there is also ademand for colourful or exotic species for thetrade - and species like 'Claret Fighting Fish'(Betta livida), 'Bellicose Betta' (Betta bellica),'Giant Fighting Fish' (Betta, new species) and'Harvey's Licorice Gouramy' (Parosphromenusharveyi) fit the requirements very well.

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Conservation of the Malaysian blackwaterichthyofauna

The current literature review and studies, usingthe North Selangor blackwater peat swamp for-est as a case study, show that there is great po-tential for research work to be carried out inblackwater peat swamps. Contrary to publishedliterature, blackwater swamps are not species-poor and low in biomass. The number of fishspecies recorded at present from the North Se-langor peat swamp forest far exceeds those ob-tained in previous collections. It shows that thefauna, at least where freshwater fish is concernedis not poor, and strongly suggests, especially inthe discovery of four new species, that there ismuch to learn and discover in this neglected habi-tat, which is fast losing ground to human exploi-tation and encroachment. As has already beendemonstrated in several studies (see Prentice,1990), the conservation and proper managementof peat swamps is important not only in ensuringthe survival of a rich and poorly studied, uniqueecosystem, but also as a natural resource fromwhich to tap water, timber and fishes for humanuse.

The value of wild aquarium fish has not beenwidely discussed in scientific communities otherthan with concern for endangered species such asIkan Kelesa or Golden Dragon Fish (Scleropagesformosus). The freshwater aquarium fish resourceis a very lucrative trade. In Singapore, this tradeexceeded US$50 million in 1990, and althoughmuch of this is in cultured species, a significantproportion consists of wild-caught fish (Ng,1991). Johnson et al. (1969) noted some of thespecies they felt were valuable and discussed thepotential of harvesting Malaysian wild fishes forthe aquaria. The aquarium trade however, hasgrown greatly since. Concern about overexploit-ing the fish resources are of course valid (seeAlfred, 1968; Tweedle, 1961; Johnson, 1961;Johnson et al., 1969). This has led to proposalson banning collections and exports (or imports)in some countries keen on conservation, but un-fortunately, this idea is too simplistic and doesnot really help conservation ultimately.

We observed that virtually all the areas sampledby us have been logged before. In fact one par-ticularly rich stream flows through an oil palmestate from the swamp forest. The high fish di-versity in these areas suggests that selective andcontrolled harvesting of timber apparently doesno real immediate damage to the peat swampforest ecosystem. In fact, the Asian WetlandBureau has drawn up several proposals in favourof controlled logging in the North Selangor peatswamp forest (see Chan, 1989; Prentice, 1990).Similarly, Davies & Abdullah (1989) recommendthat landuse in the peat swamp should be basedon the retainment of forest cover and avoidingtotal land clearance. Within this proposal, propermanagement of the habitats and controlled har-vesting for the aquarium trade will enable the localpopulation to derive long term, direct financialreturns from conserving the main swamp forestarea.

The value of the aquarium trade is not oftenobvious as complete records and data are lack-ing. In Indonesia for example, many unregisteredforeign collectors organise large scale 'harvests',with the live fishes exported directly back to theircountries without passing through local authori-ties. Undoubtedly this also occurs in Malaysia, toan unknown degree. This has led local authoritiesto underestimate the value of this resource. To getjust a rough idea of the value of the resource athand, we calculated the profits of selling, for ex-ample, 1000 individuals of each of the 25 specieswe have recognised here as worthy of theaquarium trade. The individual species costs arebased on what we know of retail prices in Sin-gapore. In Europe and America, prices are almostcertainly much higher. The retail profit amountsto at least US$12000. While such an exercise ispurely hypothetical and approximate, it gives arough idea of what income to expect if the re-sources are properly managed. Considering thesize of the forest, extent of the swamp forestdrainage and biomass of the waters, very largenumbers of some of the smaller species might beharvested without serious impact on their popu-lations, as long as it is properly managed. Someaquarium species such as Sphaerichthys osphro-

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menoides or Macrognathus circumcinctus, whichthe published literature regards as rare or endan-gered in Malaysia, are in fact, common in acidicblackwaters, the species being common enough inthese habitats to sustain controlled exploitation.It is our belief that retention of the intact forestis more crucial to the survival of these species inthe wild than an ineffectively conceived but per-haps well meaning total ban. A problem associ-ated with the current fish trade that must be men-tioned is that many of the specimens collected donot reach their eventual destinations (i.e. aquar-ists) and even when they do, most do not live verylong. The compromises involved in harvesting thewild fishes for economic gain and trying to reducethe tragic waste of so many lives are many.

Johnson (1968) had commented that the chem-istry of blackwaters tends to limit productivity,and indicated that '... high fields of fish can beobtained from ponds built on gelam lands [withblackwater] if the water is limed and treated withphosphate' (p. 309). He realised the conflictingproblems of producing traditional food fishesagainst that of valuable aquarium species, al-though he felt that blackwaters are poor to mod-erately good for only a few species of aquariumspecies. Our study suggests otherwise.

The association between the loss of specificblackwater habitats and the fate of a species canbe perhaps best exemplified by Betta persephone,a beautiful belontiid recently described bySchaller (1986). It is known for certain only fromone small stream - its type locality near AyerHitam in Johor. This locality has been developed,a new highway and other projects have destroyedmost of the forest in the area. The species can befound only in the remnants of the peat swamps inthe Ayer Hitam area. It appears however, that thespecies also occurs in several areas south of AyerHitam, and some specimens from this area havebeen imported into Germany for the aquariumtrade (pers. observ.; M. Kottelat, pers. comm.).It can only be hoped that the habitats whereB. persephone still occurs, which are almost cer-tainly vulnerable, can be protected in the nearfuture.

It is unfortunate that detailed surveys such as

ours in North Selangor peat swamp forest arenow no longer possible in Johor, where the mostextensive peat swamps and blackwater habitatsin Peninsular Malaysia once occurred. It wouldbe pointless to speculate what undiscovered orunrecorded species once occurred in these black-waters. A small hint of its vast wasted potentialcan be perhaps gleaned from the discovery of theblackwater snakehead Channa bankanensis in thewestern remnants of the Johor peat swamp for-ests. It is however, not impossible that some ofthese species (like C. bankanensis) still survive (al-beit rather tenuously) in small and as yet, intactblackwater areas, and await discovery. System-atic surveys should be made in these areas beforedevelopment completes its coup-de-grace onsouthern Malaysian blackwater habitats.

Acknowledgements

Mr Duncan Parish of the Asian Wetlands Bureaufirst broached the idea of a detailed fish survey inthe North Selangor peat swamp forest, andthroughout this exercise, he has been most help-ful. Mr Jonathan Davies and Mr Abdullah Rahimkindly shared their observations and experiencesof their first survey with us, and provided manyuseful tips. Dr Maurice Kottelat (Munich Mu-seum) and Dr Tyson Roberts (California Acad-emy of Science) were, as always, generouslyforthcoming with their help and advice in identi-fying many of the taxa. Dr Susan Lim (Univer-sity of Malaya) was infectious with her enthusi-asm and urging us to make known our findings.Discussions with Dr Mohd. Zakaria-Ismail (Uni-versity of Malaya), Dr Guy Teugels (TervurenMuseum), Dr Jorg Vierke (Husum, Germany),Mr Dietrich Schaller (Munich, Germany), Pro-fessor Yong Hoi Sen (University of Malaya), DrRichard P. Lim (Australia) and Datuk Chin PuiKong (Sabah Fisheries) were helpful on taxo-nomic and ecological aspects during the collationof this report. We are grateful to Dr Mohd.Zakaria-Ismail for so generously permitting usthe use of his unpublished thesis. Dr MauriceKottelat, Dr Tyson Roberts, Dr Mohd. Zakaria-

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Ismail and an anonymous reviewer kindly re-viewed the manuscript. Field assistance by theDepartment of Zoology (National University ofSingapore) Honours class of 1991, Mr TommyTan, Ms Diana Chia, Mr Jeffrey Lee, Mr AbdulLatiff bin Zainal, Mr N. Sivasothi and Mr LauChing Ong is much appreciated. This study hasbeen supported by a research grant 910410 to thefirst author from the National University of Sin-gapore.

Note added in proof

A new genus and new species of minute cyprinidwas recently discovered from the North Selangorpeat swamps and is currently being described byK.-E. Witte. This is a stenotopic blackwater spe-cies. The number of fishes now known from thepeat swamp totals 48.

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