FISHES and FORESTS: the IMPORTANCE of SEASONALLY FLOODED RIVERINE HABITAT for 島'le KONG RIVER FISH FEEDING

NAT. NAT. HIST. BULL. SIAM Soc. 55(1): 121-148 ，2∞ 7

FISHES AND FORESTS: THE IMPORTANCE OF SEASONALLY FLOODED RIVERINE HABITAT FOR 島'lE KONG RIVER FISH FEEDING

Ian Ian G. Baird 1

ABSTRACT

The Mekong Ri ver supports a rich diversity of fish species and seωonally inundated ripar- i組 forest habitats ，including those in the Siphandone Wetlands in Khong District ，Champasak Pr ovince ，southem Laos and adjacent areas in Stung Treng and Kratie Provinces in northeastem Cambodia. Cambodia. However ，there has been little systematic research done regarding the relationships between between fishes 釦 d seasonally flooded forests in the Mekong River Basin. Th is paper confirrns 血at 飽町民凶al plants ar 芭 important food sources for some important fish species ，by means of a study of fish stomach contents conducted at Ban Hang Kh one ， a rural fishing village situated on 組 island in the Mekong River just below the Khone Falls. A total of 1， 617 fish specimens belonging belonging to at least 73 species ，52 genera and 20 families were examined. At least 35 species

offo 陀 st 企ui 臼， 13 species of fresh leaves ， and 3 species of flowers were found in fish stomachs a1 0ng with bark ，roots and a wide variety of other fish foods. Species in the family Pangasiidae were were found to be the most important consumers of fruits and other fresh vascular plant material. Hypsibarbus Hypsibarbus spp. ， Tor tambroides. Le ptobarbus hoeveni (Cyprinidae) ，Osphronemus exodon (Ospronemidae) (Ospronemidae) and other fishes a1 so consume considerable amounts of plant m 副 er. V iIl agers mentioned mentioned 73 plant species believed to be consumed by fishes ，including 9 suitable baiting for hooks hooks for catching fish. Th e importance of seasonally inundated fl 日間sts to the aquatic ecosystem of of the Mekong Ri ver is considered ，including the possible role of fishes as plant seed dispersers and and predators. F1 00ded forests along the Mekong River are threatened by hydrological changes caused caused by the construction of large dams both up and down river.

Key words: Cambodia ，fish diet ，自 sh fe 沼ding ，flooded forests ，Laos ， wetlands

INTRODUCTION

There are often important relationships between freshwater fish species and seasonally inundated vegetation ，or flooded forests. In the tropics ， fish-forest feeding relationships in the Amazon River Basin have been particularly well studied (GOULD 町 G ， 1980; 1983; 1993;

GOULDING & FERREIRA ， 1984; ARAuJO ・LIMAETA L.， 1998; SAINT-PAULETAL. ， 2000). In 肱 Mekong Ri ver Basin and other parts of Southeast Asia ，many f同shwater fish 紅 'e known to feed on forest fruits and other seasonally flooded vegetation (ROBERTS ，1993) ，but there has been su 叩risingly little research done to document the feeding habits of 仕eshwater fish in relation relation to seasonally inundated forests.

'Geography 'Geography Department ，University of British Columbia ， B.C. Vancouver. ， Canada; and Global Association for People People and the Environment (GAPE) ，p. o. Box 860 ，Pakse ，Lao PDR. Correspondence: 1235 Basil Ave.. Victoria. B.C. ，Canada V8T 2G 1. Email: [email protected] Received Received 19 April 2006; accepted 25 February 2007.

121 121 122 122 IAN G. BAJRD

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Figure 卜 Th 巴 Lower M 巴kong River Basin ，sh ow ing rh e locat ion of th e Siphandone Wetlands ，in Khong Di st ri ct， Champasal く Province ，so uth e rn Lao PDR PJSHES PJSHES AND PORESTS 123

The seasona ll y inundated riparian habitat of the southern-most part of the Lao Peop l巴's Democratic Republic (Lao PDR or Laos) and northeast 巴rn Cambodia constitutes an important important part of the aquatic 巴cosystem ofthe Mekong River Bas in .The Siphandon 巴Wet land s in in Khong District ，Champasal くProvince ，south 巴rn Laos-and areas along the Mekong River between between Kratie Province in northeastern Cambodia ， and the border between Laos and Cam bodia bodia in Tha laborivath District ， Stung Tr 巴ng Prov in ce-support some of the most important seasona ll y inundat ed habitats and associated fish populations (ROBERTS ， 1993; CLAR lD GE ， 1996; 1996; BAII ミo ET A L.， 1999 ;DACONTO ， 2001; BARAN ET AL. ， 2005). The Khone Falls are situ - ated ated in th 巴 southern-most part of the Siphandon 巴刻化tlands (F ig. 1) ー The objective of this study was to investigate the feeding patterns of various Mekong

River River fish species found near seasonally inundated forests in the Khone Falls 創 'ea in order to gain gain a b巴tter und 巴rstanding ofthe relationships betwe 巴n fish and seasonally inundat 巴 d forests. A lth ough preliminary r巴sults are given for 73 fish specie s，detailed data are provided for only thos 巴 species found to consume significant amounts of seasonally inundated vegetation .Lo- cal cal knowledge regarding the relationship between fishes and seasonally inundat 巴 d riverine habitat habitat in the お1ekong Riv 巴r in southern Laos and northeastern Cambodia was also utilized.

In In this paper 1 consider th 巴 possible repercuss i ons of seasonally flooded riverine habitat destruction destruction on indigenous fish populations and biod iversity in the Mekong River Basin ， and consequently consequently on the local people who depend on wild-capture fisheries for subsistence and ll1 come ，巴 sp 巴cially w ith r巴gard to the construction of large dams upriver.

援2貌頭 Se 臨a酪s州。町ona 問刷n1旧凶a副11 刷y引刊川lげ川n礼出山削削山叩山州Jr川川川un町附、K吋糊由蜘di拍a

一-一 _ Int 出erna 副 ti 旧。 na 副Iboundary Villages Villages Ban 1 Ban Don Tholathi 10 Ban Don I.S om Ban 2 Ban Don Sa ng 11 Ban Don $a t1。、 g 8an 3 8an Don 001 Tok 12 Ban H oun Sadam 8an 4 8an Oon Del Oke 13 Ba nDon Phapheng CAMBODIA 8an 5 8an Don En ~ 4 Ban Hang Khone Ban 6 Ban Don Ton Tok 15 Ban H ang Sadam Ban 7 Ban Don Tan Oke 16 8an Veun Gnang 8an B 8an Khone Tai 17 Ban Don Langa 3km Ban 9 Ban Khone Neua 18 8an Veun Kham

Pigure Pigure 2. The K hone Pa ll s in K h ong D istri c t，in th 巴 low e rpart of the Siph andone Wetland s ，in Champa sak Pro vin ce ， so uthern Laos. The Pa ll sc ro ss th e midd l巴 of th e map from w 巴st 10 eas t. 124 I州 G. BAIRD

STUDYAREA

百 e Siphandone Wetlands are situated in the mains 田 am Mekong Ri ver in the southem- most part of Laos and consists of a complex system of channels ，rapids ，deep water pools ， waterfalls ，1紅 ge and small inhabited and uninhabited isl 佃 ds ，and various kinds of seasonally inundated inundated forests (CLARIDGE ， 1996; DACONTO ，2001). 百le Kh one Falls is a series of waterfalls and channels running p紅 allel 企'om west to east in the southem-most p釘 t.of the Siphandone Wetlands Wetlands (Fig. 1). Ban (village) Hang Kh one ，where the study was conducted is situated on Don (island) Kh one ，which straddles 由e Falls (Fig. 2， #14).

FLOODED FORESTS

百le seasonally inundated wetland habitat of Siphandone and adjacent parts of northeastem Cambodiais 郎副ke other seasonally flooded 紅 'eas in the Am azon basin or even the Tonle Sap Lake of Cambodia. In the Am azon ， large floodplain areas are inundated for many months each each ye 釘出 a result of varying rainfall pattems in different p紅 ts of the basin ，creating ideal conditions conditions for fish habitation. In many ways the flooded rivers of the Am azon are a product of of hydrological conditions similar to those of 血e Mekong ， but the fish and plant species are entirely entirely di 妊erent (Go ULD 町 G ， 1980; 1983; SAINT-PA 肌 ET AL. ， 2000). In In Cambodia ， the annual reversing of the direction of the Tonle Sap River during the the rainy season contributes significantly to the Tonle Sap Lake being filled up by the high-waters high-waters of the Mekong River (LIENG ET AL. ，1995) ， expanding the inundated 紅白from 2，520 km 2 加出e 也y season to a peak of 15 ，780 km 2 in the rainy season (RA 別 BO 四， 1996). ROLLET (1 972) recognized the Tonle Sap forest to be of largely endemic or autochthonous origin ，and evolutionarily related 旬， but not identical with ，forests 也at occupy rip 紅 ianzones of of the Mekong Ri ver. He noted the shared presence of Crateva ，Cynometra ，Homonoia ， Hydnocarpus ，and Samandura in the Tonle Sap 紅 'ea and along the Mekong proper ， but also pointed out pointed a number of key plant species in the flooded forests of southem Laos and northeastem Cambodia 白紙紅'e absent in the Tonle Sap Lake. Th ese include Ficus racemosa L. var. var. racemosa (Moraceae) ，An ogeissus rivularis ， Acacia harmandiani ，and Telectadium edule ， to to name a few. McDONALD ET AL. (1997) confrrmed 白紙no more 血an 20% of the vascular plant plant species found in flooded forests in the Tonle Sap Lake 紅 'e also found in and along the mains 回創n Mekong in southem Laos and northeastem Cambodia ，and most of those 出at do exist represent secondary and upper-floodplain species. Th us ， the relationships between fishes fishes and forests can be expected to differ. Critically ， the riverine flooded forests discussed here 紅 e associated with a largely linear river river system with seasonally moderate-to-fast flowing water ， unlike the lacustrine-like environment found in the Tonle Sap Lake in Cambodia where water levels rise without associated incre 回目in water velocity. 副R ipa 釘ria 佃npμlant 飽si 加na 叩ndalon 略喝1gt 白hema 姐a adaptt 柏ot 由heswi 負rainy sea 邸soncuη'en t. Substrate in the Tonle Sap Lake is also m a:紅 rkedly diι fおeren 飢lt ， with sands and silts dominating ， whereas rocky 紅 eas dominate northeastem Cambodia and southem La os (ROBERTS & BAIRD ， 1995; RAINBa 四， 1996; DACONTO ，2001). 官leamount of flooded area changes immensely in the Tonle Sap Lake ， while along the Mekong River in southem Laos and northeastem Cambodia horizontal flooding is much less extensive. FISH ES AND FO R ESTS 125

Figur e 3. Typi ca l floo cl ed fore st area during th 巴 clr y seaso n below th e Khon e Fa ll s nea rH ang Khon ev illa ge ， Khon g D istr ict，C hamp asak Pr ov in ce ，Lao PDR

Figllr e 4. Lar ge nooclecl fore st ar ea clllrin g th e clry seaso n jll st abo ve th e Kh one Fa ll s，Khon g Di stri ct，C hampa s叫くProvin ce ，Lao PDR 126 126 IAN G. BA IRD

Figur e 5. F i cus racemos α L. var. racemosa (M or aceae) tr ee and rip e fruit s (m . ak deua in L ao) adja cen tt o th e M eko ngR ive rn ea rH ang Kh onev ilI age ，Kh ong Oi stri ct，C hamp as は Pro vin ce ，L ao PD R. M anyf ish spec l巴S 巴at th ese fruit w h en they fa lI int o th e wate r，a nd thef ruit sa rea l so use d as bait to ca tch so m 巴 fish spec ies 、vith hooks

Figur e 6. Cayra liα lrifolia (L.) O om . va r. Iri(o Li a (V itaceae) ripe frll its (mak houn in Lao). T h ese fruit s aJ芭 lI sed as ba it to catc h fish w ith h ooks ，espec ialI y Pα ngasius polyuranodon (pa gnone hang hian in

Lao) the rain y season fro m the Meko ng R i ver below th e K hone Fa lI s 旧 H ang K honev ill age ，K hong O istrict ，C ham p asak Prov in ce ，Lao PDR FISH ES AND FORESTS 127

Figllre Figllre 7. A n exa mpl e of a Pall gasiu.¥" pol yurallodoll F iglll 官 8. A n 巴Id erl yexper i巴ncecl fi sh er fro m Sa ngv 1i - 。?a gllon e hall g hia /J in Lao ) fi sh ca ug ht 011 lage ，Khon g Di stri ct，C hamp asak Provin ce ， a f1 0ating hook bait ecl w ith Cα yral lCl ll ぴ'o lia Lao PDR c1 emonstrate s how C raleva m ~川gα

(し) Dom. v出 tr げ'o lia (V it aceae) rip ef rll its (Lo ur. ) D C. (Ca pp ar aceae) l eaves (bai kow "I!

(nwk hou n. in Lao) 川 the M 巴kon g River in La o) are u sed to fish bait hooks to ca tch

n巴ar H ang Khone vill age ，Kho l1 g Di str ict ， m ainl y Pall gas ius bocourli (p a nyang in Champasak Province ，L ao PDR Lao ). If the leav 巴sa re 11 0t posit io l1 ed 011 the hook the ri g ht way ， there is no hop 巴 of ca tchin g any fi sh，e mph as i zes th e fisher 128 128 IAN G. BA IRD

F igur 巴 9. P angas iu s ple ur olae n. ia (p a n. yone rh ong kho /11. in Lao) ，o ne o f the impor ta nt fish spec i es in th e H ang Kh on巴 vill age ar ea th at ea ts tl oocle cl fo res tl eaves a ncl frlli t

Fi gllr e 10 . Pαngas i us con chop hi lus (pa pho (I arge s izecl fish ) a ncl pa ke (s m all size cl tish) in Lao )，o ne of the im por ta nt fish spec i es in th 巴 H an g K hon e vill age area that ea ts flooclecl fo rest 1巴ave s ancl frllit FISHES FISHES AND FORESTS 129

There 釘 'e many types of inland ‘flooded forests' throughout the world. Here ，‘ seasonally ally inundated riparian or riverine habitat' or ‘flooded fores t' is defined as the area up to and including including the moving littoral zone which is subject to sporadic flooding or inundation as a direct direct or indirect result of seasonal changes in the water levels of the Mekong River or her tributaries. tributaries. It It is not yet known how much seasonally inundated riparian habitat exists in northeastem Cambodia and southem Laos ，and while it is unlikely to be anywhere close to the area surrounding rounding the Tonle Sap Lake (RAINBOTH ， 1996) or the 300 ，000 km 2 in the Amazon Basin (SA 町 T-PAULETA L.， 2000) ， these forests do ，nonetheless ， play an important ecological role in the the aquatic ecosystem. In all cases ， these habitats are closely linked to seasonal hydrological conditions. conditions.

The seasonally inundated habitat of southem Laos and northeastem Cambodia c佃 be classified classified in many ways. ALTOBELLI & DACONTO (2001) and MAXWELL (2001) recognized distinct 7 distinct wetland categories in the Siphandone Wetlands in terms of flora. However ， for the pu 中 oses of this study ，it is useful to divide the wetland forests directly adjacent to or within the the mainstream river bed into 3 main groups. The first 1 term ‘riparian vegetation usually not flooded'. flooded'. Th is includes 均arian 回 es and plants ，which are usually flooded for only short periods periods (a few days) during the rainy season ，and rarely inundated for long periods (several weeks). weeks). These trees often hang over the Mekong River during the high-water season when most fruiting occurs (ALTOBELLI & DACONTO ， 2001). One of the most important groups of 企uiting trees 紅 e figs Ficus spp. (Moraceae) ， but there 紅 e many other species which also provide provide fruits ，leaves ，flowers ， barks and roots that are eaten by fishes (ROBERTS ， 1993; BAIRD ， 2001). The second category can be classified as true ‘ flooded forest'. It is primarily situated in the the mainstream Mekong Ri ver ，and its plant species 紅 'e specially adapted to survive up to 6 months of partial or total inundation during the rainy season. They also flourish during the dry season season when not under water. Fruiting generally occurs late in 由e dry season or very early in the the rainy season before water levels rise. These species also shed all their leaves when they

釘 'e inundated ， to reduce resistance to strong high-water currents. Thick 2-3-m tall shrubs dominate dominate certain areas ， while sparse shrubs cover other rocky areas (ALTOBELLI & DACONTO ， 2001; 2001; MAXWELL ， 2001). Some key plant species found in these areas include Crateva manga (Lour.) (Lour.) DC. (Capparacea.e) ， Telectadium edule H. Bail l. (Asclepiadaceae) ，Homonoia riparia Lour. Lour. (Euphorbiaceae) ， Rotula aquatica Lo ur. (Boraginaceae) ，and Phyllanthus jullienii Beille (Euphorbiaceae) (Euphorbiaceae) (ALTOBELLI & DACONTO ， 2001; MAXWELL ， 2001). This type of habitat dominates dominates the mainstream Mekong above the Khone Falls because of hydrological factors; where flood levels are relatively lower compared to below the falls (ALTOBELLI & DACONTO ， 2001; 2001; DACONτ '0， 2001). The third category is another type of ‘flooded forest' occurringjust below the Kh one Falls in in southem Laos and extending south into northeastem Cambodia as far as Kra tie Province (AL- TOBELLI & DACONTO ， 2001; MAXWELL ， 2001). Ban Hang Khone (Fig. 2) si is 加 ated adjacent to to this kind of true ‘ flooded fores t'. Trees and other plants found there are especially adapted to to survive up to 6 months of total or partial inundation during the rainy season between May and October ，when water levels rise from 6 to 8m (ALTOBELLI & DACONl ひ， 2001; MAXWELL ， 2001). 2001). Fruiting generally occurs in the late dry season ，and leaves are shed during the flood season. season. Many plant species 紅 e 出e same as those found in the Mekong River bed above the Falls ，including Homonoia r伊aria. However ，two species of current-bent ， deciduous trees up 130 IAN G. BAIRD

t 'O 10 m tall d'O minate these areas ，viz. Anogeissus rivularis (Gagnep.) Le c. (C 'O mbretaceae) and Acacia harmandiana (Pie 町 e) Gagnep. (Le gumin 'O sae ，Mim 'O s'O ideae) ，b'O th 'O fwhich 釘 e alm 'O st absent ab 'O ve the Falls (MAXWELL ，200 1). Th ese f'O rests 紅 .eapp 紅 .ently unique t 'O this p訂 t 'O f the Mek 'O ng River ， as they have speci a1 physic a1 and hydr 'O l 'O gical requirements ，including cluding rocky substrate f'O r anch 'O ring r'O'O ts ，a1 紅 ge seas 'O na1 change in water level ，and high water water vel 'O city during the rainy seas 'O n. 官lese 訂 'e harsh c'O nditi 'O ns f'O r plants t 'O survive in ， and 邸 a result in s'O me areas plant diversity is l'O w (MAXWELL ， 2001).

METHODS

All All 'O f the fish exarnined during this study were caught just bel 'O w the Kh'O ne Waterf a1 1s ne 紅白e La 'O /Camb 'O dian b'O rder by 10 fishers 企om Ban Hang Kh'O ne (Fig. 2). Th e fish examined ined were identified ，their weights and lengths rec 'O rded ，and st 'O mach c 'O ntents exarnined in the the field minutes after the fish were landed. All data were c 'O llected 'O ver an extended peri 'O d between 1993 and 1999. The vast m 司j'O rity 'O f species had well defined st 'O machs. Th e field c'O nditi 'O ns did n'O t make preservati 'O n 'O f the st 'O mach c 'O ntents f'O r future study p 'O ssible. Th e fish were a1 1 caught using set m 'O n'O /multi-filament nyl 'O n gillnets with 2.5 t 'O 20 cm mesh sizes (kang mong) ，cast-nets (he) ，dr 'O p-d 'O'O r bamb 'O'O basket traps (chan) ，and h'O'O ks (bet) (bet) baited with land earthw 'O rms ，m 'O le crickets (F 創凶ly Gryll 'O talpidae) ，and Cayratia trifolia (L.) (L.) D 'O m. var. trifolia (Vitaceae) fruits (see CL 成田GE ET AL. (1 997) and DEAP ET AL. (2003) f'O r Mek 'O ng fishing meth 'O d descripti 'O ns). M 'O st were landed either ar 'O und 0600 h 'O r 1800 h， but a1 m 'O st a1 1 'O f 血e Pangasius polyuranodon were caught in the late m 'O ming 'O r early aftem 'O'O n using f即日'O ating h'O'O ks and lines tao) (bet baited with C. trifolia fruits. N 'O 'O ther species species were caught using this fishing meth 'O d. Al l fish were exarnined within a few h'O urs (m 白血lU m 12) 'O f being caught by gillnets ，h'O'O ks ，'O r 回 ps ， because the fishers checked their fishing fishing gear at least twice a day ， in the early m 'O ming and in the evening. M 'O st fish died 'O nly m 'O ments bef 'O re their st 'O machs and intestines were cut 'O pen. L 'O cal fishers with c 'O nsiderable kn 'O wledge 'O f seas 'O nally inundated riverine habitat and fishes fishes were s'O metirnes asked t 'O help identify s'O me 'O f the f'O rest 仕uits and leaves f'O und in fish fish st 'O machs. Sec 'O nd and third 'O pini 'O ns were s'O licited when deemed pruden t. In cases when p 'O sitive identificati 'O ns 'O f fish st 'O mach c 'O ntents c'O uld n'O t be made ， the c 'O ntents were simply designated designated ‘miscellane 'O us 企uits' ，‘ miscellane 'O us leaves' ，etc. It It was n'O tp 'O ssible t 'O quantify the am 'O unt 'O f each substance c'O nsumed ， as is s'O metimes d'O ne(Go 瓜 D 町 0& 日限EIRA ，1984). 百 eref 'O re ，substances listed f'O ra fish st 'O mach indicate presence presence 'O nly. During the c'O urse 'O f investigati 'O ns ，a number 'O f experienced fishers fr 'O m Ban Hang Kh'O ne and Ban Hang Sadam (Fig. 2) were interviewed regarding flooded f'O res t/ fish relati 'O n- ships ，which helped br 'O aden my understanding. T 'O remain c'O nservative ，1 have 'O nly included inf 'O rmati 'O n that the maj 'O rity of villagers interviewed were in agreement 'O n. 日SHES AND FORESTS 131

RESULTS

Fish Fish Stomach Con 飽ntsStudy

Th e st 'O mach c 'O ntents 'O f1 ，617 fish specimens bel 'O nging t 'O 20 families ，52 genera ，and at least least 73 species were examined (Table 1). Further d'O cumentati 'O n，inc 'O叩'O rating inf 'O rmati 'O n fr 'O m interviews with l'O cal fishers and literature ，is pr 'O vided f'O rs 'O me fish species speci 貧困 cally cally selected due t'O也 e relatively high 'O ccu 町'ence 'O f fl 'O'O ded f'O rest 合uits and vegetati 'O n in their their st 'O machs.

FAMILY CYPRINIDAE (CARPS AND MINNOWS)

Hypsibarbus Hypsibarbus lagleri.- Tw 'O specimens (220 and 150 g) 'O f 出 is c紅 p were examined. One had green leaves and b'O th had pulverized bark in their st 'O machs. 百lis species pr 'O bably c'O nsumes c 'O nsiderable am 'O unts 'O f plant matter 仕om seas 'O nal1 y inundated f 'O rests during 血e rainy rainy seas 'O n. RA 町 BO 咽(1 996) rep 'O rted 伽 tthis species feeds 'O n Z'O'O p凶 tkt 'O n，w 'O rms and algae ， but it und 'O ubtedly eats m 'O re.

Hypsibarbus Hypsibarbus malcolmi. - F 'O rty- 'O ne specimens 'O f this c紅 p were examined (25-3 ，400 g，mean 500 g). Thirty specimens were examined between July and N 'O vember ，and 50% 'O f th 'O se had large am 'O unts 'O f gr ，田 n leaves in their st 'O machs ，3 had filament 'O us algae ，2 had fine fine algae ，and 2 had eaten an unidentifiable dirt-like substance 'O r detri 加 s and pulverized bark. bark. One each had grasses ，insects ，r'O'O ts and f'O rest 合uits ，and 2 had empty st 'O machs. Eleven specimens specimens were examined during the dry seas 'O n between March and early May. One had small small ga 柑 op 'O d snails in its st 'O mach ，and an 'O ther had larger 'khe' gastr 'O p'O ds. Thr ee had eaten eaten large 創 n 'O unts 'O f filament 'O us algae ，1 had eaten leaves ，and 1 had an empty st 'O mach. The data indicate that this carp feeds heavily 'O nf 'O rest leaves during the high-water seas 'O n and relies mainly 'O n algae and snails f'O rf 'O'O d during the dry seas 'O n.

Hypsibarbus Hypsibarbus pierrei. - F 'O ur specimens 'O f this migrat 'O ry species were examined in April and May 1994 (110-510 g) ，and all had gastr 'O p'O ds in their st 'O machs. One als 'O had leaves ， and an 'O ther had bark and the seeds 'O f the n 'O n-native riverine plant species ，Mimosa pigra L. (Mim 'O s 'O ideae). Vi llagers rep 'O rt 白紙Ol is fish feeds 'O nb 'O白金凶 ts and leaves in the fl 'O'O ded f 'O rests during the high-water seas 'O n. Snails are believed t 'O be the species' main s'O urce 'O f f'O'O d during l'O w-waters.

Hypsibarbus Hypsibarbus we 仰 orei.- τwenty-f 'O ur specimens 'O f 由is species were examined (115- 1，600 g，mean 573 g). 百rree were examined between January and March. One 'O f th 'O se had filament 'O us algae in its st 'O mach ，an 'O ther fine algae ，and 2 had leaves. Tw enty- 'O ne were ex- m 叫nedin 也 e rainy seas 'O n (May -O ct 'O ber): 81 % had green leaves ，14% had grasses ，14% had filament 'O us algae ，1 had fine algae ，1 had pulverized bark ，1 had r'O'O ts ，and 1 had c'O nsumed the leaves leaves 'O f the fl 'O'O ded f 'O rest shrub Phyllanthus juillienii Beille (Euph 'O rbiaceae). This sp 配 ies cle 紅 ly relies heavily 'O nf 'O rest leaves f'O rf 'O'O d in the rainy seas 'O n， while c'O nsuming algae in 出 e dry seas 'O n. It s meat is 'O ccasi 'O nally t'O xic t 'O humans in the high-water seas 'O n，app 紅 'ently because because it eats t'O xic fl 'O'O ded f'O rest 合uits like th 'O se 'O f Hydnocarpus anthelminthica Pierre ex Lanessan Lanessan (Fl ac 'O urtiaceae) and Samandura mekongensis Pierre (Simar 'O ubaceae) (BAIRD ET AL. ，1999). 百le seeds 'O fb 'O出 plants are t'O xic (SMITH ， 1945; ROBERTS ， 1993). H 'O wever ，even when the meat is t'O xic ，it apparently causes 'O nly slight dizziness and nausea. 132 132 IAN G. BAIRD

Tor Tor tambroides. ー Only 3 specimens of this uncommon 1紅 ge cyprinid species were ex ・創世間d (9.2 kg ，95 cm (百 J); 2.4 5 kg ，60 cm; and 7 .4 kg ，84 cm). Only found in fish catches at at Ban Hang Kh one during November and December ，when large adults 釘 e caught in gillnets (BAIRD ET AL. ， 1999). One specimen had a stomach full of forest fruits ，including 'mak sam p加が(unidentified 企凶 t) and Coccinia grandis (L.) Voigt (Cucurbitaceae). There were also many flooded forest leaves ， such as those of Aegle marmelos (L.) Corr. (Rutaceae) ， 'bai ta deng' deng' (unidentified le af) and others. An insect ，called 'meng khap' (unidentified) was also found. found. Th ere were numerous 合uits and seeds that were unrecognizable because they were crushed crushed beyond recognition - this fish masticates its food. Another specimen had pulverized b釘 k，and 也e 出ird had grasses ，pulverized b紅 k and one gastropod snail in its stomach. T. tambroides tambroides is notorious for eating poisonous 仕uits such as Hydnocarpus anthelminthica and Samandura harmandii (ROBERTS ， 1993). Some villagers repo 氏自at 由e meat is safe to eat in the the low-water season or when its eyes 紅 e not red ， but nobody ever eats its intemal org 釦 S (BAIRDETAL. ， 1999).

Le ptobarbus hoeveni.-Six specimens of this 1釘 ge cyprinid species were examined during during the rainy season (1. 9-3.75 kg ，me 佃 2.62 kg). 1¥v o had empty stomachs ，1 had consumed 'khai ping' yellow algae ，2 had eaten unidentifiable forest 仕uits ，and 1 had the 仕uits of Diospyros Diospyros sp. (Ebenaceae) and Ficus heterophylla L. (Moraceae) in its stomach. Th e species conducts conducts local trophic migrations to and 企om inundated forests (RA 町 BO 百I， 1996). Most Hang Kh one villagers w i1l not eat its meat ，and especially its intemal organs ， as it also eats 白 e fruits of 的 dnoca 中 us anthelminthica and Samandura harmandii. However ，preserv 泊g 出e meat with salt (called 'pa som') makes it edible (BAIRD ET AL. ，1999). 百lis species also sometimes masticates the seeds of 仕uits it consumes.

FAMILY PANGAS llD AE (CATFISHES)

Pangasius Pangasius bocourti. - Forty-one specimens of 白is important species were examined (5-2 ，200 g，mean 465 g). 百lis species has a varied diet ，consuming mainly leaves and 合uits in in the rainy season and fish ，mollusks ， algae and shrlmp ，amongst other things ，during 血e dry dry season. Table 2 lists the items found to have been consumed by the species ，回 well as 3 other pangasiid catfishes 白紙 also have varied diets. Experienced vi1l age fishers catch P. bocourti bocourti at the height of the high-water season by baiting hooks with Crateva manga leaves. A fisher w i1l approach a half submerged C. manga tree and check whether fishes have nibbled the the leaves that are touching the water. If they have ，he w i1l tie a line with hook to the 佐山lk or or branches and carefully bait it wi 血 3 C. manga leaves. Th e bait and hook 紅 e left to flicker at 也e surface of the water next to 血e tr ，田. It takes a special skill to correctly bait the hooks ，加 d 也is method is used p釘 ticul 紅 Iy to catch 血is species.

Pangasius Pangasius conchophilus. - A to 凶 of216sp 民国.enswereex 創世間d(2 -4， 300 g，mean216 g). g). Table 2 includes a breakdown of the contents of the stomachs examined. P. conchophilus

has has a varied diet and is a gluttonous eater (R OBERTS & Vm 叩 AYANON ，199 1). A 140 ・g specimen was found to have over 200 small gastropods in its stomach ，and many other specimens had 50 to 100 small snails. Snails are especially important in the low-water season (J anu 紅 yto May). Dense green algae is an important food between January and March. Forest fruits and leaves leaves are the dominant foods between late April and September ，and leaves are important in September and October. In the rainy season ， P. conchophilus is often caught with long-line FISHES AND FORESTS 133

h'O'O ks baited with Cのratia trifolia fruits ，earthw 'O rms ，and m 'O le crickets (Family Gryll 'O- talpidae). talpidae). In late May 'O r early June it undertakes an ec 'O n'O mically imp 'O rtant and large-scale migrati 'O n upriver and it is the main species caught in large wing traps (li) in the rapids bel 'O w andin 也e Kh'O ne Falls (ROBERTS ， 1993; ROBERTS & BAIRD ， 1995; BAIRD ET AL. ， 2004).

Pangasius Pangasius hypopthalmus. -Six specimens 'O f血is large catfish were exar 凶ned (35 0- 1，000 g，mean 717 g). Five had empty st 'O machs and 'O ne had c'O nsumed small unidentifiable 企uits. It It pr 'O bably eats f 'O rest vegetati 'O n and fruits during the rainy seas 'O n. RAINBO 叩(1 996) lists its its diet as fishes ，crustaceans and vegetable debris.

Pangasius Pangasius larn 閣 ldii. - Fifteen specimens 'O f 血is highly migrat 'O ry pangasiid catfish were examined (1 25-2 ， 100 g，mean 964 g). All specimens were examined in the rain y: se 踊'O n between May and Oct 'O ber. Five fish had empty st 'O machs ，6 had F. racemosa 企uits ，2 had 'mak 'mak hai' Ficus sp. (M 'O raceae) fruits ，2 had e紅白w 'O rms ，1 had crickets and 2c 'O ntained an unidentifiable unidentifiable dirt-like substance 'O r detritus. 官邸species feeds heav i1 y 'O n fruits and leaves during during the rainy seas 'O n，and is 'O ften caught 'O n F. racemosa fruit-baited l 'O nglines at the beginning ginning 'O f the rainy seas 'O n.

Pangasius Pangasius macronema. ー τoirty- 由ree specimens 'O f由is highly migrat 'O ry and ec 'O n'O mically cally imp 'O rtant species were examined (10-105 g，mean 41 g). All but 2 spec 加lens were examined during the high-water season. Three had c'O nsumed F. racemosa fruits ，1 had Crateva Crateva trifolia fruits ，8 had unidentifiable leaves ，1 had pulverized wood ，1 had 5 pieces 'O f 佃 unidentifiable mushro 'O m ，2 had e紅白w 'O rms ，2 had mole crickets ，2 had ants ，1 had a 'douang' 'douang' beetle ，2 had 'meng peng' insects ，1 had a ‘bong ki' insect ，1 had eaten a 'meng po' po' dragonfly insect ，6 had consumed 'O ther unidentifiable small insects ，7 had an unidentifiable able dirt-like substance 'O r de 凶tus ，and 1 had unidentifiable material. This fruit ，leaf ，and insect-eating insect-eating species is caught 'O n ho 'O ks baited with mole crickets (Family Gryll 'O talpidae) ， land land earthw 'O rms and C. trifolia fruits. RA 別 80 叩 (1996) listed its diet as consisting 'O f 'O nly aquatic aquatic insects ， but it obviously c'O nsumes a wide variety of foods. It undergoes important migrations migrations ups 住e創 npast 血e Kh one Falls ，where it supp 'O rts an imp 'O rt 佃 tcommunal fishery (BAIRD ET AL. ， 2001).

Pangasius Pangasius pleurotaenia. - Th irty-nine specimens of 出is imp 'O rtant flo 'O ded forest species cies were examined (5-110 g，mean 59 g) (Table 2). A1 though RA 町 80TH (1996) listed its diet diet as consisting of terres 凶 al and aquatic insects as well as a small amount of plant matter ， it it may be more herbivorous 由anRA 町 80 百I suggested ，especially during the rainy season. P. P. pleurotaenia also feeds 'O n1 紅 ge quantities 'O f the fl 'O wers of Telectadium edule ，when 血ey 紅 e bl 'O oming and fall into the water in N 'O vember and D 回 ember. Pe 'O ple 合omDon 百101a 出i vi1l age ，which is just ab 'O ve the Kh one Falls in Kh ong Di strict (Fig. 2) ， often bait set h'O'O ks and lines and longlines with the fl 'O wers 'O f T. edule t 'O catch this species. Pangasius Pangasius polyuranodon. - Two hundred and eighteen specimens were examined (5 0- 1， 150 g，mean 309 g) (Table 2). RA 町 80 百(1 996) listed P. polyuranodon's diet as consisting sisting 'O f insect larvae ，b'O tt 'O m-dwelling w 'O rms and submerged plants ， but it has a much m 'O re varied varied die t.百lI s glutton 'O us eate れoften f'O und with a full stomach ，consumes 1紅 ge amounts of of forest leaves and 仕uits in the high-water season (June ベ)ct 'O ber). It was mainly caught in deep waters using free fl 'O ating ho 'O ks and lines (bet ω 0) baited with Cayratia trifolia fruits between August and November. 官le species feeds very close t 'O the surface during the high- 134 IAN G. B AlRD

waterse 錨'O n，and is pr 'O bably a heavy c'O nsumer 'O f dense green algae in the l'O w-water seas 'O n. Al 14 'O f the specimens examined in February 1994 had st 'O machs full 'O f algae. It als 'O appe 釘 S t 'O c'O nsume many insects during the m 'O ns 'O'O n seas 'O n. Th is 'O mniv 'O rous species als 'O eats fish ， snails ，crabs ，shrimp ，and even frogs ， but n'O t in large quantities.

Pangasius Pangasius sanitwongsei. - Eight small specimens 'O f this species 'O f endangered giant ca 凶 sh (GROOMBRIDGE ， 1996) were examined. Alth 'O ugh the species can reach 'O ver 200 kg in weight ，villagers 貨om Hang Kh'O ne did n'O t catch any 泊dividuals weighing 'O ver 1.5 kg between 1990 and 1999. F 'O ur small specimens examined in 出e dry seas 'O n had empty st 'O machs and 'O ne had leaves in its st 'O mach. Three specimens (150 ，85 ，and 75 g) were exar 凶ned in July 1994. 1994. Tw'O had insects in their st 'O machs ，and 2 had large am 'O unts 'O f Craveta manga leaves. Juveniles Juveniles are s'O metimes caught 'O nh 'O'O ks baited with Cayratia trifolia fruits ，e 紅白w 'O rms 組 d fish. fish. V i1l agers rep 'O rt that it especially likes t 'O eat rotten meat ，and l'O cals have l'O ng baited large hand-made h'O'O ks ，called 'bet pa leum' wi 由 r'O fish tten ，d 'O g，bu 首ru 'O， chicken ，etc.

FAMILY OSPHRO 阻 MID 組 (GIA 悶 GOURAMIES)

Osphronemus exodon. Only 'O ne specimen (50 g and 14 cm) 'O f this recently described Mek 'O ng endemic (ROBERTS ， 1994) was examined ， in September 'O f 1996. 1t had pulverized b紅 k ，r'O'O ts and insects in its st 'O mach. Like its cl 'O se relative Osphronemus goramy ，it is an imp 'O rtant c'O nsumer and inhabitant 'O f inundated f 'O rest vegetati 'O n. ROBERTS (1994) rep 'O rted 白紙it feeds mainly 'O n plant material ，including fruits ，leaves ，and fl 'O wers ， with s'O me insects and crustaceans. Y 'O ung fish may feed m 'O re 'O n insects ， while adults are likely t 'O c'O nsume m 'O re plant plant matter (R OBERTS ，1994). 百le extra 'O rdinary 'O ral dentiti 'O n 'O f this species ，including r'O ws 'O f enlarged t白血'O n the external surface 'O f the jaw and entirely 'O utside 'O f the m 'O uth when shut ，may facilitate plant and especially ro 'O tf 'O raging and feeding. D 'O n Th'O lathi vi1l agers use h'O'O ks and lines baited with the Telectadium edule fl 'O wers in N 'O vember and December t 'O catch O. O. exodon. H 'O'O ks are set near the surface in n'O n- fl 'O wing p'O'O ls surr 'O unded by fl 'O'O ded f'O rest. E 紅白w 'O rm-baited h'O'O ks catch it in p'O'O ls am 'O ngst wetland f 'O rests during the dry seas 'O n. In March andApril this species c 'O llects vege 旬.ti 'O n using its c'O mplex set 'O f teeth in 'O rder t 'O build nests nests ne 紅 the b'O tt 'O m 'O fp 'O'O ls 0.5-1.0 m deep. Th e female stays inside 白 e burr 'O w 'O f the nest f'O r 'O ver am 'O nth during the spawning seas 'O n while the male ‘gu 紅白， just 'O utside the nes t. This This is 血 e 'O nly Mek 'O ng fish species kn 'O wn t 'O c'O ns 凶 ct a nest using vegetati 'O n.

In In summary ，we f'O und at 'O tal 'O f at least 35 species 'O ff 'O rest 仕uits ， 13 species 'O f fresh leaves ，and 3 sRecies 'O f fl 'O wers in fish st 'O machs. Barks and r'O'O ts were als 'O f'O und in a number 'O f fishes. M 'O st 'O f the 仕uits ， leaves and fl 'O wers were f'O und in pangasiids. Cyprinid fishes in 血 e genus Hypsibarbus 紅 e imp 'O rtant leaf eaters. 1 have pr 'O bably underestimated the actual number 'O f fruit and leaf species c'O nsumed ，because 企uits and leaves f'O und in fish st 'O machs were s'O metimes unidentifiable 'O r unkn 'O wn t 'O us.

Villager Villager In terviews

V i1l agers claim 也at Channa spp. ， Morulius spp. ，Bangana behri ，La beo erythropterus ， Hypsibarbus Hypsibarbus spp. ，Osphronemus exodon and 'O thers fishes are 'O ften f'O und inside the submerged 加 nks 'O f large f 'O rest tr ，田 s like Anogeissus rivularis and Acacia harmandiana. V i1l agers ex- pl 'O it ぬis si 加ati 'O n by putting gi1l nets ne 紅白e 'O penings 'O f these refuges and bang the trunks t 'O scare the fish int 'O白 e waiting nets. FISHES FISHES AND FORESTS 135

Other Other species of season aI ly inundated riverine flora such as Homonoia riparia and 1き1- ectadium ectadium edule are aI so believed to slow water flow and thus create important refuge habitat for for fishes. Morulius spp. 紅 'e sometimes speared (lem) when they 紅 'ehiding 創 nongst inundated vegetation vegetation during the rainy season. Villagers Villagers highly vaI ue flooded forests ，re aI izing that they serve as important habit for wildlife ，especi aI ly indigenous fish and other aquatic animals. Th ese habitats aI so serve as essential essential commons 釘 'eas where villagers fish; ex 回 .ct medicinal plants ，edible 企uits ，and vegetation; vegetation; and various harvest wood products. They 紅 'e critic aI for 10c aI livelihoods.

Fi shing with Fru its Leaves and Flowers

Th e following forest 合uits ，leaves and flowers were identified by villagers at Ban Hang Sadam and Ban Hang Kh one as being suitable for baiting hooks for fishing: 1) ‘mak khika' (unidentified fruit-possibly passion fruit) can be put on hooks to catch Osphronemus exodon. 2) ‘mak kham pome' (unidentified fruit). 3) 3) Hydnocarpus anthelminthica fruits can be put on hooks to catch Tor tambroides and other other fish species. 4) 4) Ficus racemosa fruits can be put on hooks to catch many species ，especi aI ly pangasiid gasiid catfish. [This species was incorrectly identified as Ficus variegata B l. var. variegata (Moraceae) (Moraceae) in ROBERTS (1 993).] 5) 5) Crateva manga leaves can be put on hooks to catch Pangasius bocourti. 6) 6) Cayratia trifolia fruits can be put on hooks to catch many species. 7) 7) Nauclea orientalis fruits can be put on hooks to catch many species. 8) 8) Telectadium edule flowers can be put on hooks to catch mainly Pangasius pleurotaeni α and some Hypsibarbus malcolmi ， Hypsibarbus wetmorei and Osphronemus exodon. 9) 9) Diospyros pilosanthera Blanco (Ebenaceae) 台uit can be put on hooks to catch many fish fish species. Eight Eight out of the 9 types of fruits ，leaves and flowers identified above were found in the the stomachs of fishes during this study. Only Nauclea orientalis (Rubiaceae) was not found. Th e above information is important as it helps indicate food preferences for fishes and aI so helps helps link fish species to the forests.

Di versity of Natural Fish Foods

Table Table 3 includes a list of some forest fruits ，日 owers ，leaves ，and roots that Ban Hang Kh one and Ban Hang Sadam villagers claim that Mekong River fishes in their area regularly feed feed on. There are 72 nomin aI species of flora and their plant parts included. Of those ，it has so so far been possible to apply some level of scientific taxonomic identification to 58 species. However ，this list is undoubtedly far 企om complete. It does ，however ， demonstrate fish that rely rely on a large number of plant species ， not just a few. 136 IAN G. BAIRD

DISCUSSION

The Fishes and the Forests

百lere 紅 'e many indirect ec 'O l 'O links gical between fl 'O'O df 'O rest habitat and fish in 血e Mek 'O ng. Many insects rely heavily 'O n seas 'O nally inundated riverine habitats f'O rf 'O'O d and shelter ，and in turn ，fish rely 'O n these insects as imp 'O rtant f'O'O ds 'O urces. F 'O r example ，ants 紅 e abundant abundant 'O n the tree Flacourtia indica (Burm f.) Meπ'. (Fl ac 'O町 tiace 鵠)， and fish are kn 'O wn t 'O c'O ngregate under these trees ，where 出ey feed 'O n 鉱山由at fall int 'O白 e water. Th e fish Toxotes Toxotes microlepis spits water up int 'O plants 泊'O rder t 'O kn 'O ck insects int 'O the water bef 'O re it it feeds 'O n them (SMI 百五 1945). Many 'O ther fish species feed 'O n insects 白紙 fall int 'O也 e water. water. In the Am az 'O n ，fishes rely 'O n insects that fall 合'O m 由 ec 佃'O py as f'O'O d，and GOULDING (1 993) rep 'O rted 白紙80 species 'O f fish 也 at eat insects 紅 'ekn 'O wn 合om the Ri'O Negr 'O， many 'O f which fed 'O n 紅白r'O p'O ds ，particularly beetles and spiders. Fl ying insects ， ants and m 'O le crickets crickets appe 紅 t'O be 曲em 'O st c'O mm 'O n insects f'O und in fish st 'O machs in the Mek 'O ng. As in the the Am az 'O n (GOULD 町 G ，1993) ，1d 'O n'O t kn 'O w 'O f any fish species 白 at eat 'O nly 'O ne 'O ra few kinds kinds 'O f insects. It appe 紅 S 血.a t， as in the Am az 'O n， smaller fish species are the main insect eaters eaters and are generally m 'O re successful at catch 泊 g insects. Shrimps ，crabs ，snails ，and bivalve m 'O llusks als 'O rely heavily 'O n fl 'O'O ded f 'O rests f'O r habitat habitat and f'O'O d.τ 'h ey 紅 e numer 'O us am 'O ngst the fine r'O'O ts 'O f many seas 'O nally inundated shrubs shrubs and trees such as Anogeissus rivularis and Ficus spp. 百lese aquatic animals c'O nsti- tute tute an imp 'O rtant s'O urce 'O ff 'O'O df 'O r many species 'O f fish. S'O me species 'O fz 'O'O pl 鉱山'O nand phyt 'O plankt 'O n als 'O rely 'O n inundated plants. In In the Amaz 'O n Basin fishes feed mainly 'O n dec 'O mp 'O sing leaves rather than fresh leaves (GOULD 町 G ，1993) ， but in the Mek 'O ng there are a number 'O f species 白紙 feed heavily 'O n 仕'esh leaves ，including the 'O sphr 'O nemid ，Osphronemus exodon ，all species 'O f pangasiid catfish except except f'O r Helicophagus waandersi ，all species 'O f the cyprinid Hypsibarbus ，Le ptocheilus hoeveni ， Tor tambroides ，and 'O thers. Detritus is als 'O as 'O urce 'O ff 'O'O df 'O r many fish species in in the Mek 'O ng. It It s関 ms likely 白 atm 佃 y fish utilize seas 'O nally inundated riparian habitat as imp 'O rtant spawning spawning and nursery gr 'O unds. The y'O ung 'O f many species pr 'O bably rely heavily 'O n seas 'O n- ally ally inundated f 'O rests as refuges f'O r av 'O iding predati 'O n during the high-water seas 'O n. 百lese 紅 'eas are als 'O rich feeding gr 'O unds. M 血 y small cyprinid fishes rely 'O n seas 'O nally inundated riverine habitat in the Mek 'O ng Ri ver t 'O shield themselves fr 'O m str 'O ng currents during the beginning 'O f the high-water seas 'O n. Vulagers Vulagers use branch-bundle fish-attractant pull- 回.p s ，called '肋 a' in La 'O， filled with vegetati 'O n t 'O catch these fish. Small cyprinid fishes ，including Henicorhynchus lobatus ， Henicorhynchus siamensis ， Crossocheilus reticulatus ，Lo bocheilus melanotaenia ，and Pristolepis fasciata 釘 'e mainly caugh t.官 lis fishing meth 'O d can 'O nly be effectively used between May and July. Later ， water levels are t'O'O high and many 'O f the small cyprinids species migrate d'O wnriver (BAIRD ET AL. ， 2003). L. melanotaenia ，al 'O ng with small quantities 'O f 'O ther small cyprinids ，釘 'e als 'O caught by villagers with their bare hands in July and August when they can be f'O und very very cl 'O se t 'O sh 'O re and 創 n'O ngst vegetati 'O n. M 'O st 'O f these smaller species were n'O t carefully investigated investigated during 血is study ， but that sh 'O uld n'O t imply that seas 'O nally inundated 釘 'eas are n'O t imp 'O rtant f'O r them. Seas 'O nally inundated riparian habitats serve many 'O ther imp 'O rtant ec 'O l 'O gical functi 'O ns such as creating shade f'O r fishes ， reducing the evap 'O rati 'O n 'O f water ，and FISHES FISHES AND FORESTS 137 preventing preventing soil erosion (CLARIDGE ， 1996; BAIRDETAL. ， 1999; DACONTO ， 2001). Although morphological adaptation in fishes speci 白cally related to 仕uit feeding has not been observed in the Amazon Basin (GOULDING ，1983) ，1 believe 白紙 the extraordinary oral dentition dentition of the Mekong endemic goramy Osphronemus exodon ， noted above ，may be an evolutionary evolutionary adaptation designed to facilitate feeding and foraging on roots and other plant matter. matter.

Fi sh 錨 Seed Dispersers and Seed Pr edators

Fishes Fishes in the Mekong Basin have not previously been shown to play an important role as as dispersers of plant seeds through the consumption and defecation or regurgitation of fruits and In seeds. fact ， outside of South Am erica there have been few reports of 企ugivorous fishes fishes (GOULD 町 G ，1983) ， although CHICK ET AL. (2003) have provided some information about about fishes as seed dispersers in North Am erica. Frugivorous fishes have not been reported 仕om inland areas throughout continental A 企ica ，and in South Asia only a few species have been reported in the literature (GOULDING ， 1983). SMITH (1 945) reported 白紙也.e cyprinid Leptocheilus Leptocheilus hoeveni feeds on the large fruit of the chaulmoogra-tree 同Idnocarpus (目acour- tiaceae) ，叩dWH 汀 MORE (1 975) reported that the walking catfish Clarias batrachus eats the fleshy 企uits of Gonystylus bancanus (Miq.) Kurz (Th ymelaenceae). Th ere have also been a few marine fishes ，like catfish in the genus Arius 白紙 feed on fruits in mangrove forests. However ，GOULDING (1980; 1983) has provided convincing evidence that fish in the Amazon Basin Basin play important roles as seed predators and dispersers. Seed predator fishes crush and masticate masticate seeds ，killing them. Fishes 白紙 disperse seeds 紅 e defined as those 血at often swal- low fruits whole and generally do not damage the protective coatings of the seeds wi 白 their teeth teeth or guts. However ，even fishes that 紅 e essentially seed predators ， such as 由e characins of the Am azon ，disperse some seeds because not all the seeds they consume 紅 'e crushed and masticated masticated (GOULD 町 G， 1983). Many fishes in the Mekong may well be both seed predators and dispersers. However ，1 have not been able to identify a single fish species that is entirely frugivorous. Thi s is probably because because fruits 紅 'e not available all year round. Pangasiid are catfishes potentially the most important important seed dispersers in the Mekong River because ，like many ca 出 shes in the Amazon ，血.ey have poorly developedjaws and teeth (ROBERTS & VIDTHAYANON ，199 1).百 is results in catfishes catfishes generally not being able to masticate seeds of the fruits 出ey eat (GOULDING ， 1983). 1 have observed many whole fruits in the stomachs of the 9 species that 1 have found to be fruit fruit eaters ，and 1 did not find masticated fruit seeds in their stomachs. Although characins ， the main group of Am azonian seed predators ， are not found in 出e Mekong Basin ， at least two species of cypri 凶ds from the Mekong can be described as seed predators: お r tambroides and Le ptobarbus hoeveni. As wi 出 characins ，some of the seeds 泊 the stomachs of these species were not masticated. Therefore they could be both seed dispersers dispersers and predators. GOULDING (1983; 1993) states that in the Amazon catfish and characins are 血 .e principal fishes 白紙 disperse seeds ，and 也 at fish-dispersed seeds 釘 'e associated with fleshy fruit material ，which is what makes the seeds attractive to the fishes as food. He has also shown that seed seed coats of seeds are not destroyed during digestion-either by characins or ca 出 sh. He also also believes 白紙 the buoyancy of many fleshy fruits in water is not only advantageous for water water dispersal ， but conveniently positions 企uit at the surface where 白ey can be easily found 138 138 IAN G. B AlR D by fishes. In the Mekong Ri ver the siltiness of the river makes visibility low at the bottom so so when 合uits 釘 e ne 釘 the surface 白ey 釘 'e much easier for fish to find. Figs are 加 portant fish fish foods in bo 血 the Am azon and the Mekong (GOULD 町 G ， 1983; BAIRDETAL. ， 1999). Most other 仕uits 血at fish feed on in the Mekong ，including figs ， are buoyant ，佃 d some pangasiid catfishes ， including Pangasius polyuranodon and Pangasius pleurotaenia ， stay ne 紅白e surface surface during the main fruit feeding season. Go ULD 町 G (1 983) has pointed out that even if catfish catfish had developed enough teeth to masticate seeds ，出 ey would still not be able to crush 出e many small seeds of figs.τ 'h us figs are well adapted for dispersal by fish although it is unclear unclear if 出ey are the selective agents.

Asin 出.e Am躍。 n (GOULD 町 G ，1983) ，m 佃 y of the possible seed dispersers of the Me- kong Ri ver 釘 'e highly migratory. Some p加 gasiid catfishes 紅 e known to undertake long seasonal seasonal migrations up the mains 位e創 n Mekong (ROBERTS & BAIRD ， 1995; BAIRD 町、 AL. ， 1999; 1999; BAIRDETAL. ， 2001; BAIRDETAL. ， 2004; HOGANETAL. ，2004) ，andhence may disperse seeds seeds far upriver. GOULD 町 G (1983) has suggested the same for characins 佃 dca 出 sh in 出e Am回 on ，and expects that seeds remain inside fishes for between 1 and 7 days. However ， for the the Mekong evidence is stilllacking. In the Mekong ，pangasiid ca ぜishes could be dispersing seeds seeds upriver ， but some pangasiids eat lit t1 e to nothing during strong migratory periods. For example ，P. krempfi have empty stomachs when 由ey migrate past Hang Kh one (BAIRD ET AL. ， 2004). 2004). Another pぽ allel between the Mekong and the Amazon is 也atmany of 出e expected migratory migratory seed dispersers in both river systems 紅 e found in large whitewater rivers.

The Importance of the Fl ooded Forest of the Mekong

Th e information presented herein ， including the empirical stomach contents data and theexpl 組制ons of other ecological relations between fish and forests ， demonstrates the role of of riparlan vege 旬.tion as sources of food ， as shelter for prey ，and as habitat for fishes of the m 泊ns 住eam Mekong River in northeast Cambodia and southem Laos. 1t appe 釘 S血at pangasiid ca 凶 shes heavily depend on forest 仕uits and vegetation 邸 food so 町 ces ，especially in the rainy rainy season. Many others ， like cyprinids ，Hypsibarbus spp. ， Tor tambroides ，Le ptobarbus hoeveni ，and the osphonemid ， Osphronemus exodon 釘 'e also at least pぽ tially dependent on forest 企uits 加 d se 錨 onally inundated vegetation as direct sources of food. It is also possible that that some of these species con 凶bute to the propagation of seasonally inundated forests by dispers 泊g the seeds of fruits 血ey consume ， although some probably also destroy most seeds 也創出ey consume. Small fish species were not carefully considered in 也is s旬 dy ， but many 訂 e probably heavily heavily dependent on flooded forests for food. Other carnivorous and algae-eating fish species probably probably rely heavily on flooded forests for habitat and indirectly for food. Some s戸 cies of fish fish may utilize flooded forests as spaw 凶ng and nursery grounds. Seasonally inundated riverine erine habitats constitute important habitat and food so 町 'ces for a varlety of species of insects ， shrimps ，crabs ，snails and microorganisms 白紙自由 feed on. Seasonally inundated riverine habitats habitats also serve a number of other important ecological functions ，and are important habitat for for birds ，reptiles and mammals. Basically ， the whole aquatic ecosystem of the mainstreani Mekong Ri ver is closely linked to seasonally inundated areas. Because of the linkag~s between fish populations ， the flooded forests ，and the well being of the local people in southem Laos and northeastem Cambodia ， the survival of these forests is is critical (BAIRD &孔 AHERTY ， 2005; BAIRD ， 2006). Seasonally inundated habitats riverine 日SHES AND FORESTS 139

紅 'e probably some of the richest and most significant fish feeding grounds and habitats in the the Mekong Ri ver Basin. This can be seen by 血e fact 血at Ban Don Sang Island ，which is situated situated nextωa large wetland forest area just above the Kh one Falls (Fig.2) ， reported the highest highest fish catches per f. 鉱凶ly out of 由e 14 villages surveyed (BAIRD ET AL. ， 1998). It is believed 白紙 these high fish catches are 1紅 gely associated wi 出 the richness of the wetland forests forests surrounding the vi1l age. As in the Amazon Basin (GOULD 町 G ，1993) ，intemational attention in SoutheastAsia in recentye 紅 s has focused on the destruction oftropical forests in upland watersheds. More ef- fort fort needs to be devoted to conserv 泊 g riparian forests in northeastem Cambodia and southem Laos ，as 血ey 紅 'e important to the riverine ecology and associated local livelihoods.τbese wetland wetland habitats have been severely degraded along much of the Mekong River on the Lao- Th ai border as well 部 in other parts of 血e Mekong Basin. Hydrological changes caused by 由econs 甘uction of large dams in the Mekong Basin represent some of the most serious 也reats ， through through habitat destruction caused by direct inundation in reservoir areas ，and hydrological induced induced changes in c1 uding downstream erosion ，which has already been shown to be a serious problem in 由e case of 白e Yali Falls dam in Vietnam ，and downstream impacts in 血e Sesan Ri ver in northeastem Cambodia (BAIRD & MEACH ， 2005; FIS 田町田 OFFICE ，RATANA KlR I PROV 町 CE & NTFPPROJECT ， 2000). Retuming to the three flooded forest habitats described at 出e beginning of this paper ，it is is difficult to assess which of 仕lese habitats is relatively more or less important for fish species ，as 白ey serve different p町 poses and benefit different species during different seasons. For example ，m 佃 Y of the plant products consumed by fish come from 'riparian vegetation usually usually not flooded'. The second category of flooded forest listed earlier is also an important source source of plant-based fish foods ， but the third category ，which in c1 udes the tallest riparian tree species ，apparently is less important as a direct food source for most fish species. However ， the second 組 d third categories are certainly much more than important the first category insofar as as fish habitat is concemed. Th us ， while the third category may be less important as a source of of food ，it could make up for that 白rough the important role it plays as habita t. In any case ， all all these habitats 釘 'e extremely vulnerable to changes in hydrological conditions caused by large large dams. Already ，it appears that changes in the hydrology in the mainstream Mekong Ri ver caused caused by upriver dams in China may be the cause of the deaths of large numbers of flooded forest forest trees in 血e Mekong Ri ver in Stung Treng Prov 加ce ， northeastem Cambodia. We need to recognize the immense value of these seasonally inundated rip 紅 ian forests for for fish ，and locallivelihoods dependent on fish ，and 出 e potentially serious impacts of large dam construction to these critical habitats. We need to work toge 白er to sustainably use 組 d protect 白e Mekong's flooded underappreciated habitats ， for present and future generations.

ACKNOWLEDGMENTS

Th 創 lks to Bounpheng Phylavanh ，Bounhong Mounsouphom ， Phongsavath Kisouvan- nalath ，Vixay Inthaphaisy ，Kh amsouk Xaiyamanivong ， Peter Cunningham and Boun 白ong Vongsenesouk for their assistance in identifying fish stomach contents ，and also to Songma ， Sai ，Th a，Nin ，Phonexay ，Vilay ，Sounthone ，Mai ，Keo ，Sone ，Sit ，Veng ， Sout and Yeun for allowing allowing us to examine the stomach contents of their fish. Thanks to Sit ，Chan Kh oun ，Chan Nou ，Souay and Sout for their invaluable assistance with identifying flooded forest plants 140 140 IAN G. BAIRD and flooded forest fruits found in fish stomachs. Mr. J. F. Maxwell identified the flooded forest forest plant specimens 佃 d provided comments on an earlier draft. Thanks also to Mr. Klaus

Berkmueller for reviewing an earlier dra 負. Mr. Ole Heggen from the Ge ography Dep 紅 t- ment ofthe University ofVictoria ，Canada ，prepared 白e maps. Th e research conducted 仕om 1993-1997 was done under the auspices of the Lao Community Pisheries and Dolphin Pr o- tection tection Project ，and the work done between 1997-1999 was done through the Environmental Pr otection 佃 d Communi 旬 Development 泊 Siphandone Wetland Pr oject ，implemented by 出e NGO CESVI Cooperation and Development and funded by the European Commission. 百四tk: s also for the detailed comments provided by two anonymous referees and the editor ， Warren Brockelman.

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# F創叫 ly & Species Lao Name De' 甘iωs Plant Fruitsl Al gae Zo oplankton Insects Mollusks Shrimps Crabs Fish E紅白worms Matter Matter Seeds

1 I NOTOPTE 則 DAE Notopterus Notopterus notopterus pa ω ng na x xxx xx X? x x 2 I Chita /a b/a nci pa ωng 初i x x X? x xx X? xxx X? CLUPEIDAE CLUPEIDAE 3 I Tenualosa thibea ut/a ui pa makphang xxx XX? CYPRINIDAE CYPRINIDAE 4 I Am blyrhynchichthys 附 ncatus pa 加 po XX? XXX? XXX? 5 I Barbodes altus pa vianfai XX? X? xx x x X

6 I Cirrhinus cirrhos ω pa nang chan XX? XX? 同』 7 I Cirrhinus microlepis pa phone XX? xxx iZ0 8 I Cirrhinus molitorella pa keng X? XXX? ・∞〉困問。 9 I Cosmochil ω，加rmondi pa mak ban x x xx xx x Cyclocheilichthys 10 Cyclocheilichthys enoplos pa chok xx x xx X? xx .X? X? X? x 11 11 Cyclocheilichthys spp. pa doke ngieu x X? XXX? 12 12 Cyprinus carpio pa nal x X X? X? X? X? X? X? 13 13 Gyrinoche il. ω pennacki pa ko xxx X? X? 14 14 Hampa /a macrolepidota pa sout X xx xx X? X? X? 15 15 Hypsibarbus lagleri papakpe xxx X? X? X? X? X? 16 16 Hypsibarbus malcolmi pa pak kom x xxx X? xxx X? x 17 17 Hypsibarbus pierrei pa pak ta leuan ， xx X X? X? xxx 18 18 Hypsibarbus wetmorei papak 幼am xxx X? xx X? 19 19 Lab eo cf. erythropterus pa va so 脱 mg xxx 20 20 Le ptobarb 附 hoeveni paphong XX? xxx X? X? X? X? X? X? 21 21 Lo bocheilus melanataenia pa khiang xx xxx X? 22 22 μIciosoma bleekeri pa mak vai XX? XX? XX? X? X? X? X? 23 23 Mekongina ery 出rospila pa sa ・i xxx 24 24 Osteochilus me 加， ωtpleurus pa nok khao x XXX? X? X XXX? 25 25 Probarbus jullieni pa eun deng x X? x X? x x X? X? 26 26 Puntioplites falc 砕r pa sakang xx xx xx x xx # Family & Species Lao Name De 凶加S Plant Frui tsJ AIgae Zoo plankωn In sects Mollusks Shrimps Crabs Fish E紅白 worms Matter Matter S回 :ds 27 27 Raiamas guttatus pa sanak xx xx 28 28 Sikukia gudgeri pa 幼ao na x x x 29 29 Tor tambroides P由 ko ω xx xxx X x BAGRIDAE 30 30 Bagrichthys macracanthus pa mak 幼an xxx xx X? X? xx mak mak kheu 31 31 Bagrichthys macropterus pa kou の souk xxx XX? X? X? XX? 32 32 Pseudomystus siamensis pa khi hia xx x x xxx x X? X? xx 33 33 Mystus singaringan pa khagneng X? xxx X? 34 34 Hemibagrus nemurus pa kot leuang x xx X? xx X? xx xx 35 35 Hemibagrus 的 'cki pa kot mo X? xxx xx xx x 同 36 36 Hemibagrus wyckioides pa khe 削 g xx X xx xx xx xx UHM 37 37 Belωontichthys 回 nca 伽S pa khop X X xxx 山田開臼〉 SILURIDAE 38 38 Hemisilurus mekongensis pa nang deng X xxx xx xx ZU 39 39 Kryptopterus cり'fJ topterus pa doke bo 胤 xx xx X? X? X? xx 40 40 Kryptopterus spp. pa pik kai xx X xxx X X? X? X om司 41 41 Micronema bleekeri pa nang ngeun X xxx 開句同同 42 42 Micronema micronema pa nang 幼ao x X? xxx 43 43 Ompok bimaculatus pa se 胤 m x X? X? X? XX? xx 44 Wallago at ω pa 幼ao x xxx 45 45 Wallago leeri pa 幼 oun xxx PANGASIDAE 46 46 Pangasius hypophthalmus pa souay kheo XX? XXX? X? X? X? 47 47 Helicophagus waandersi pa nou xxx X? x 48 48 Pangasius bocourti pa houa mouam X xxx xxx X? x xx X? X x X 49 49 Pangasiu$ conchophilus pa pholpa ke xx xx xxx xx X xxx xx xx x x 50 50 Pangasius kr 芭mpfi pa souay hang XX? XXX? XX? X? X? X? leuang leuang 51 51 Pangasius larnaudii papeung X XX? xxx X X? X? X? x 52 52 Pangasii ω macronema pa gnone xx xx xx X? xx X? X? x t加 mada 53 53 Pangasius pleurotaen ω pa gnone thong xx xxx x xxx X? X? x x -hs khom khom 同ムム書 Fan 首Iy &. Species Lao Name De凶佃 S Plant Fruitsl Algae Z∞pl 細企 ton In sects Mollusks Shrimps Crabs Fish E紅白wonns Matter Matter Seeds 54 54 Pangasius polyuranodon pa gnone hang xx xx XXX x xxx x x X X x hian hian 55 55 Pangasius sanitwongsei pa leum xx XX? x X? X? XX? X? SISORIDAE

56 56 Bagarius ya 庁 -e lli pa 幼e X? x xx x xx x CLARlD AE 57 57 Cla 吋'as batrachus pa douk X? x X? X? X? X? xx ARIIDAE 58 58 Ar ius stormi pa 幼at ok x x X? x xx xxx

59 59 Hemipi; 脚 10 ぬ， s borneensis pa 幼at ok xx x XXX xx X? X? xx MASTACEMBELIDAE ω Mastacemblus arma ωslfav ω pa lat x X? XX? XXX AMBASSIDAE 61 61 Parambassis wo ljJi pa khap 幼ong x X? XX? X? X? X? F20 COIIDAE XX X? X? 62 62 Co 加 undecimradiatus pa seua X? xxx ・切〉完ロ POLYNEMIDAE 63 63 Polyne~刷's long 抑 ctoralis pa chin xx x x xxx X? xx SCIAENIDAE 64 64 Boesen ω nia microlepis pa kouang x x xxx X? x TOXOTIDAE 65 65 Toxotes microlepis pa mong X? xxx X? X? NANIDIDAE 66 66 Pristolepis fasciata pa ka XX? X? x xx GOBIIDAE 67 67 Glossogobius giuris pa bou 幼ao x X? X? OSPHRONEMIDAE 68 68 Osphronemus exodon pa men XX xx xx X? X? XX? CHANNIDAE 69 69 Channa marilius or spp. pa kouan X X? X? XX? x 70 70 Channa micropeltes pa meng phou X? X? xxx X? 71 71 Channa striata pa kho X x X? X? xx xx SOLEIDAE 72 72 Euryglossa panoides pa pan gnai X? x 73 73 Cynoglossus microlepis pa lin ma X? ASHES AND FORESTS 145

Table Table 2. Stomach contents of Mekong River Pangasius polyuranodon ， Pangasius bocourti. bocourti. Pangasius conchophilus and Pangasius pleurotaenia (number indicates how many fish the item was found in) at Hang Kh one village ，Kh ong Di strict ， Champasak Province ，southem Laos.

F姐伊slus P姐伊sl 凶 Pan 胆sl 凶 Pangasi 凶 Speci 凶(L ao and La tln names) poly 町細叫on bω:our 値 conchophil 凶 pleurota 佃 la pa pa fish 5 15 2 切 ou crabs 2 2 18 。 koung koung s胎泊lp 2 。 18 。 kop kop frogs (Rana sp.) 。。。 meng meng mai miscellaneous insects 31 2 25 10 douang douang bee t1 es 。。 2 。 meng meng po 命富.g onf1 y 3 。 2 meng meng chou chi dung beet1es 5 。。 meng meng khi nai mo1e crickets (F 3I凶 1y Gryllotalpidae) 27 3 7 。 lak lak len crickets 3 。。 mol mol an 包 2 5 khikadeuan khikadeuan land earthworms 2 3 5 hoi hoi gastropods 4 4 68 。 hoi hoi ki bivalve 唱。。 16 。 hoi 幼e .g 飴位。 dods 。 3 。。 hoi hoi sai gas 凶戸ds 。。。 kouay kouay nam fruit PO 加llhia modesla (Pier 問) 22 。 3 。 Fin. Fin. & Gagnep. (Annoncaeae) koi koi fruit Amp elocissus 脚 rlini Pl. (Vitaceae) 3 。 5 。 ko 附加it Craleva 刷 nga (Lo ur.) DC. (Capp 四印刷 3 。。。 ko 脚 1eaf Craleva manga (Lour.) D C. (Cappara 閃 ae) 15 10 5 ko 附 bark Craleva 脚 nga (Lo ur.) DC. (Capparaceae) 。。。 deua deua fruit Fic 附 race. 脚 sa L. var. rac 抑制(Morac 蹴) 33 3 4 pong pong po fruit Physalis angulala L. (Solana ，印刷。。。 kheua kheua nam fruit Diospyros sp. (Ebenaceae) 13 3 。。幼 sap eua fruit ? Ipomoea obscura (L.) Ker-Gaw l. 2 。。。 (Convolvulaceae) (Convolvulaceae) hai hai fruit Ficus spp. (Moraceae) 47 4 7 lakop 仕uit Muntingia calabura L. (Tiliac 飽 e) 2 。。。 (na 加叫ized) kabao kabao fruit Hydnocarpus anthelminthica Pierre ex 2 。。 Lan essan (Fl aco 町世 aceae) ho. 肌合uit Cayra 陶 Ir 扮'lia (L.) Dom. v低 Irifolia 26 。 4 10 (Vi tac 回 .e) phan phan hang fruit (unident 出 d forest fruit) 4 。。。 sak sak fruit (teak) Teclona grandis L.F. (鴻 rbenaceae) 。。。 (na 佃叫国d) nang nang d，制加it Diospyros 脚 labarica (De sr.) Koste l. 4 2 。。 var. var. siamensis (Hωhr.) Phen .g. (Ebenaceae) lang lang nai fruit Fi c. ω helerophylla L. f. (Moraceae) 45 3 7 。 lang lang nai leaf Ficus helerophylla L. f. (Moraceae) 。。。 khai khai kham leaf Phyllanlhus juillienii Beille 18 。。。 (Euphorbiaceae) (Euphorbiaceae) khai khai k. 加 m flower Phyllanthus juillienii Beille 。。。 (Euphorbia 関節) 初rpou fruit Allophyllus cobbe (L.) Raeusch (Sapindaceae) 。。 2 kheua kheua hep fruit LI. 脚 C伺 scandens Lo ur. (Menispermaceae) 15 。 3 。 kheua kheua chi nai fruit unidentified forest vine fruit 。。。 kheua kheua chi nai leaf unidentified forest vine leaf 2 。。。 kheua kheua lam nin fruit Coccinia grandis (L.) Voi .gt 。。。 (Cucurbitaceae) (Cucurbitaceae) 146 146 IAN G. BAIRD

F阻伊謡凶 F組 gasi 凶 pan 伊 si 凶 P舗伊51 凶 Sp 副 .esα ..8 0 and La姐 nnam 凶) 卯 l抑E 盲目叫白目 booour 錨 concbopbilus pleurota 佃 ia

幼inok 刷 tG.陪 wia eriocarpa Juss. 間 iac 悶) 6 。 2 。 seng seng nam fruit Si 町nchnos n似 :-vomica L. (Lo ganiaceae) 。。。 seng 幼eua fruit 7i liacora triandra (1 白， Iebr.) Di els 。。 (Menispeerma 旬 ae) 。 kan kan houng fruit AIbizia lebeck 江..e guminc 阻ae. 4 。。 Mimωoideae) Mimωoideae) kan kan houng leaf Albizia lebeck (Le gum 泊ωae. Mimωoide 閣。。。 soum soum seng fruit Xanthophy ll. 脚 lanceatum (Miq.) J.J. Sm. 3 。。。 (Polygalaceae) (Polygalaceae) 。。 tin tin pet fruit Alstonia scholaris (L.) R. Br. v訂~ scholaris 。 (A 卯cynaωae) 加m nin fruit Coccinia grandis (L.) Voigt (Cucu 巾itaceae) 2 。。伽 ik 印刷 k fruit Telectadium edule H. Beill. 。。。 (Asclepiadaceae) (Asclepiadaceae) 伽 ikin mak leaf 陀lectadium edule H. Beill. 。。。 (Asclepiadaceae) (Asclepiadaceae) 伽 ikin mak fI ower Telectadium edule H. Beill. 6 。。。 (Asclepiadaceae) (Asclepiadaceae) 幼ai hang nakl 幼ai 幼eωleaf Rotula aquatica Lo ur. 2 。。 (Boraginaceae (Boraginaceae ) pong pong po fruit Physalis angulata L. (Sol 佃 aceω) 。。。 va va nam fruit Eugenia mekongensis Ga 俳句・ (Myrtac 伺 .e) 。。。 ngiang ngiang douk unidentified fruit 。。。 kan kan houng leaf Aめizia lebeck (Le gu 則nosae. Mimosoideae 。。 2 mak mak houm unidentified leaf 。。。幼 i ka unidentified fruit -possibly passion fruit 。。。 kadan kadan fruit Garcinia cowa Roxb. (Gu 凶ferae) 3 。。幼側po. 脚削den 凶 ed fruit 。。。 kathan kathan leaf unidentified leaf 。。。励。 unidentified fruit 。。。 kang kang pa leaf (E urophorbiaceae) (Sauropus. Breynia) 2 。 2 kath 仇 nam fruit Mimosa pigra (Mim osoideae) 。 2 。 van van leaf ? Cassia sp. 7 。。。 pheo pheo n側 leaf Polygon 脚 odoratum Lo ur. (Polygon 抑制 2 。。。 mian mian fI ower & fruit identified 。。。励。 ng leaf unidentified leaf 。。。 hak hak foi fine roots 7 。。 gna gna gr 祖sses & sedges 8 。。。幼 ithao dense gr 切 n filamentous algae 5 。 21 幼ai ping yellow algae 。。。幼ai hin fine green algae 。。。 unidentifiable unidentifiable dirt-like substanceld 豊凶仙 S 37 3 37 5 lep 脚 'u ban t即 lail of domestic pig 。。。 peanut 批 :e substance (?) 3 。。。 miscellanωus miscellanωus gr 冨sses 。 15 miscella 目的us wood 。。 3 。 miscellanωus miscellanωus Vinlω 3 。。。凶 scellaneous roots 。。。 miscellaneous miscellaneous seeds 。 7 2 miscellaneous miscellaneous leaves 76 4 16 12 miscellanωus miscellanωus fI owers 5 。。。 miscellaneous miscellaneous fruits 84 3 50 10 miscellaneous miscellaneous barks 10 3 miscellaneous miscellaneous mushrooms 。。 empty empty stomachs 。。 7 。

Total Total number of s戸cimens 218 41 216 36 日SHES AND FORESTS 147

Table Table 3. Plant species 白紙 fishers 企om Hang Kh one and Hang Sadam villages ，Khong Di s凶ct ， Champasak Province ， southem Laos ，report to be regularly eaten by fish fish from the Mekong Ri ver.

N。 La 伽 Name La o Name Calegory η'fHI Acacia Acacia harmandiani (Pierre) Gagnep.( Le guminosae ， phiman nam Tree Fruit ，Le af & Mimosoideae) Mimosoideae) Fl ower 2 Ad enia heterophylla (B I.) Kds. spp. v釘'. heterophylla kheua sap Vi ne Fruit (P: ぉs迎。 raceae) 3 Aegle 脚 rmelos Corr. (Rut 畳間e) toum T悶 Le af 4 Albizia lebeck (Le guminosae ，Mimosoideae) (naturalized) 初n houng T詑牢 Fruit & Leaf 5 Allophyllus cobbe (L.) Raeusch (Sapindaωae) kapou Tree Fruit 6 Alstonia scholaris (L.) R. Br. v低 scholaris (A 伊 cynace 低) t仇 pet Tree Fruit 7 Ama ranthus spinosus L. (Am 紅 'anthaceae ) phak hom nam Herb Le af 8 Am pelocissus 刷 rtini PI. (Vi 旬印刷幼e嗣 koi Vme Fruit 9 Anogeissus rivularis (Gagnep.) Lec. (Combretaceae) lam seng Tree R∞t 10 10 Ardisia sp. (Myrinaceae) 加 i pa soi Tree Fruit II II Azad irac 加 indica Juss. (Meliaceae) (natu 凶 ized) (neam) μ dao Tree Fruit 12 12 ? Cassia sp. phak van nam Herb Leaf 13 13 Cayratia trifolia (L.) Do m. var. trifolia (Vitaαae) 幼eua houn Vi ne Fruit 14 14 Combretum trifoliatum Ven t. (Comb 児肱鎚e) or Olea ? ben nam Shrub Root ， Flower & (Oleaceae) (Oleaceae) Le af 15 15 Coccinia grandis (L.) Voigt (Cucurbi 旬ceae) tam nin Vi ne Fruit 16 16 Crateva 刷 nga (Lo ur.) DC. (Capparaceae) koum Tree R∞ t，Fruit & Le af 17 17 Datura metel L. (Solana 閃四) kheua ba Vi ne Fruit 18 18 ? Diospyros malabarica (De sr.) Koste l. var. siamensis nang ぬm Tree Fruit (Hωhr.) (Hωhr.) Pheng. (Ebenaceae)

19 19 Diospyros sp. (Ed enaceae) 幼e胤 nam Vme Fruit

20 20 D 伊lazi 附 esculent 附， (Retz.) sw. (Athyriaceae) phak kout Herb Le af 21 21 Ed 伊ta prostra ω( L.) L. (Compωitae) gna pong pal Grasses Le af 22 22 Elaeocarpus ? grandiflorus 1. E. Sm. (Eleaeocarpaceae) 初don nam 百官巴 Flower 23 23 Eugenia mekongensis Gagnep. (Myrtaceae) va nam or va khi S恰ub Fruit mang mang 24 24 Eugenia sp. (My 同aceae) khi mot Tree Fruit 25 25 Ficus altissima BI. (Morac 蹴) hai mi Tree Fruit 26 26 Ficus heterophylla L. F. (Morac 飽 e) kheua ω ng nai Tree Le af 27 27 Ficus race 脚 'sa L. v釘~ racemosa (Morace 濁) deua Tree Fruit 28 28 Ficus rumphii B I. (Moraceae) hai pho Tree Fruit 29 29 Garcinia cowa Roxb. (Guttiferae) μ dan Tree Fruit & Le af 30 30 Grewia eriocarpa Juss. (T iliaceae) khi nok Tree Fruit 31 31 Heliotropium indicum L. (Boraginaceae) ngouang sang Herb Le af & Fl ower 32 32 Hydnocarpus anthelminthica Pierre ex Lan 鎚 san 初bao Tree Fruit & Fl ower (Fl a∞ urtiaωae) 33 33 lpomoea aquatic Forssk. (Convolvulaceae) phak bong Vine Le af 34 34 Limacia scandens Lo ur. (M enisperrnaceae) 幼el 回 hep Vine Fruit

35 35 Merremia umbellata (L.) Hal l.f .ssp. orientalis (Hall f.) phak khe 削 Vine Le af Oos t. (Convolvulaceae) 幼i初de 即 n 36 36 Mimasap なra (Le guminosae ，Mimosoideae) (naturalized) kathin nam S加ub Fruit 37 37 Mori ndJl tamyi (Pierre ex Pi t.) Craib (R ubiaceae) gno nam 加問 Fruit 38 38 ? Morindopsis capillaris (Kurz) (Rubiaceae) (#530 of sompa SOI Tree Fruit 1. 1. F. Maxwell collection Apri 1/ 98) 39 39 Muntingia calabura L. (Tiliaceae) (na 佃 ralized) takop Tr 切 Fruit 148 148 IAN G. BAIRD

No Lati n Name Lao Name Catego. 砂乃IJH!

40 40 Nauclea orientalis (1.) L. (Rubiaceae) kan leuang TI 官E Fruit 41 41 of，似 scandens Roxb. (Olacaceae) iωk Tree Fruit 42 42 Passiflora foet idJl 1. (Cucurbita 倒的 (naturalized) 幼eua gnon hang Vi ne Fruit & Le af 43 43 Phyla nodiflora (1.) Gaertn. (Gramineae) gnaphak 幼仰の Grasses Le af 44 44 Phyllanth ωjuillienii Beille (Euphorbiaceae) khai kham Shrub R∞t & Flower 45 45 Physalis angulata 1. (Solanaceae) pong po T問 e Fruit 46 46 PO 加thia modesta (Pierre) Fin. & Gagnep. (Annon 抑制 ko ω!y nam T問 Fruit

47 47 Polygonum odorat 附， 1 Lo ur. (Polygon 抑制 pheo phak nam Herb Le af 48 48 Ro ω la aquatica Lo ur. (Boraginaceae) khai hang nakI Tree Flower & Le af 幼ai 妨eua 49 49 Samandura mekongensis Pierre (Simaroubaceae) ngo ωn T問 e Fruit or or Quassia ? 50 50 (E uropho 巾， iaceae) (Sauropus ，Breynia) 初ng pa Tree Fruit & leaf 51 51 St ηInchnos n附 -vomica L. 仏og 加 iaωae) seng nam Tree Fruit 52 52 Tectona grandis L. F. (鴻 rbenaceae) (nat 町叫 ized) (teak) sak Tree Fruit 53 53 Telectadium edule H. Beille (Asclepiadaceae) 幼ai k初 mak S耐ub Fruit & Fl ower 54 54 Tetracera loureiri (Fin. & Gagnep.) Pierre ex Craib 幼eua lin het Vine Le af & Fl ower illeniaceae) (D illeniaceae) 55 55 1i liacora triandra (Colebr.) Diels (Menispermaceae) seng 幼eua Vine Fruit 56 56 Xanthophyllum lanceatum (Miq.) J.J. Sm. (Polygalac 閣 e) soum seng T陀 E Fruit ，Flower & Le af

57 57 (Asclepiadaceae) 幼e削 phak mai Vine Leaf 58 58 15 additional p加 t specie 唱 not scientifically identified Fruits ，Le aves and and Flowers