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The Critical Role of the and Tonle Sap Corridor for Tonle Sap ecology and the important Role of the Waterway Wetland in

by Touch Seang Tana

1. Introduction

For almost 20 years involving in the fisheries sector, especially the inland fisheries, a thousand doubts rise up in my mind at every step of approach on how the nature cerates this critical inland water system and its tremendous resources. Why the Tonle Sap Lake reputed as a larges fisheries productive freshwater systems for many millennia (Chu Ta Kwan, 1329, Mohout, 1857-9, Vincent, 1860-1, Petiole, 1911). What this lake was before the above period as Rainboth, 1996 quoted in his Zoogeography book that the freshwater Tonle Sap Lake aged about five thousand years and the present Mekong and Tonle Sap were only two thousand years age.

A French researcher, August Pavie,1898 was well explained in his Researcher sur L'Histoire du Camboge, du et du Siam, indicated that the whole central plain of Cambodia was a marine bay and the Mekong River reached this bay at somewhere near the entrance of the present Tonle Sap Lake (see Figure1). This latter information was well explored by geological and archeological works on textile soils and fossiles located 12 meters beneath in Samrong Sen (northeastern town), which represented the prehistoric human settlement of this region. Before the lake connected to the Mekong and Tonle Sap , neither data nor information proving the biological richness of the Tonle Sap Lake were available. Therefore, these remain doubtful until to day but Rainboth (1996) has poited out that divesification of the biological richness of the Tonle Sap Lake occurred during time that this lake was connected to the Mekong River by the Tonle Sap corridor and the importance role of the reverse water system between the Tonle Sap Lake and Mekong river. In addition, Carbonel and Guiscafre, 1963 dicovered the importnce role of the watershed of the Tonle Sap Lake, which has also contributed almost a half of the regime to the lake during rainy season. Thus not only the Mekong water but also the surrounding tributaries had played the importance role to flood the Tonle Sap Lake.

These above argument are of great contribution to my pragmatic preference for understanding the important role of this ecosystem by setting up a scientific method through an evolutionary approach to investigate this complex system. Hermeneutic is the salient point this attempt to grasp a scientific knowledge, which based on objective historical understanding. However, the history of the nature was less interested by historian in the past as political events were predominant. Even though, a critical uniqueness representing by edible aquatic animal for people livelihood was also attracted some hobbyist writer, through which we can understand some of our natural evolution.

The economic interest has turned this splendid natural ecosystem to heavy commercial exportations, which are consequence of the depletion of the utilized resources. The evolutionary change of our nature are the effect of three logical factors: the nature-nature contradicted phenomena (1), the human nature contradicted phenomena (2) and the human-human contradicted phenomena (3). The latter factor is complicated and difficult to understand as it is the effect of the two groups of people who have same or different interest on the nature. However, the environmental uniqueness and biological richness of the Tonle Sap Lake in accordance to the integration of the Mekong and Tonle Sap Rivers phenomena and its gradual change has become a critical subjects of the politician, academician, administrators, economist, biologist, environmentalist, naturalist etc. at the present time.

A serial number of publication of the foreign academician and scientists in the past and in recent period shown that the richness of fish and other animal population had no longer satisfied the economic ambitiousness of the commercial corporation and administration and especially socio-economic of local people. Management and law enforcement cannot stop this rampant situation of destructiveness due to lack of understanding of the critical problem of the commonsense of knowledge on this ecosystem. Some scientists and academician are dogmatic with inductive research for management improvement but inductive finding is far behind the critical reality of the situation. A priori of induction in scientific research is become a subject for discussion between the finding and the reality in the Cambodian inland fisheries ecosystem for convincing the manager to alleviate this environment from threat of serious deterioration. The inductive research is finally failed to prove the truth that can be used as a powerful argument to influence the decision maker.

However, we already knew that some of the most important animals have disappeared or under threat of Page 2 of 10

extinction, and that past abundance is far from ensuring future success. This is the fact, and clearly, although we could do something about is, we cannot do much. Darwin's theory of the origin of the Species and the Natural Selection is quiet clear that past abundance never ensures future biodiversity success. According to this theory, animals which are not well adapted to their changing environment perish, consequently those which survive (up to a certain moment) must well adapted. This is not the nature of an empirical theory, but is a logical truism (Popper, 1972, P.69).

To search for truth in the critical problem of the biodiversity evolution of the Tonle Sap Lake with exploitation for human benefit is my pragmatic preference in scientific discovery since this environment has changed but not too fast for long period of times, and not too radical, otherwise all life in this ecosystem and all adaptation will come to an end. In the possible way of existence, all living organism in this world are slowly adapted or sensitive to the environmental changes and changing conditions, there is therefore no reestablished harmony between the properties of the organism and those of the changing environment. Only if the organism produce mutations, some of which are adjustments to impending changes, and thus involve mutability and if the process of adjustment has gone on long enough, then the speed, fitness, and complexity of the adjustment may strike us as miraculous (Popper, 1972, p 70). We are now at that now at that stage where biological existence resists under human strike of exploitation in the Tonle Sap Lake environment. This paper described the physical, ecological and biological survival of the complexity of adjustment of the Tonle Sap Lake environment mutation according to the important waterways corridor evolving under serious human and nature pressure.

2. Logic of important ecosystem in the Tonle Sap Lake and the role of the waterway corridor for biological mutability

The Tonle Sap Lake or Great Lake in Cambodia is one of the most well-known water body covering on a very large area (2,700-3,00sqkm) during peak dry season in May and expanding 5 time bigger (15,00-16,00sqkm) during the peak flood period in late October. The Tonle Sap Lake received the flood regime from the Mekong Rivers through the Tonle Sap River between the period of June and September and on the other hand, from the surrounding stream of the northern and weather watershed (Stung Chinit, Stung Sen, Stung Storng, Stung Kampong Khleang, Stung , Stung Kralanh, Stung Monkul Borey, Stung Pursat, Stung Krakor and Stung Boribo streams) The longest and largest streams in terms of discharge water into the lake are: Stung Sen, Stung Storng and stung Sangke, which following by Stung Chinit, Stung Pursat and stung Boribo (Carbonel and Guiscafre, 1963). The physical and ecological importance of these flood supplier sources to the Tonle Sap Lake is the creation of the complex delta system consisting of a number of waterways and a huge flooding gallery forest.

The Mekong source of flood supplier has created a huge delta from Snoc Tru, Kampong Chhnang down to Peam Long Vek, at the last part of the Tonle Sap River. Stung Sen stream created a delta at Phat Sanday, . Stung stram created a delta at Tonle Chmar and Stung Sangke sream with the combination of Stung Kralang and Stung Monkol Borey streams created a second largest delta after the first delta in . The importance of the delta ecosystem are its flooding gallery forest and numerous waterways that are not dried up during dry season, which provide alterative choice for different species mutation.

Most fisheries scientists, ecologists and environmentalists consider flooding forests as a great habitat for fish and other aquatic animals in terms of feeding grounds, spawning grounds and safe shelter. But my pragmatic preference in scientific observation consider this as only part of logical truism, it is not a clear empirical finding of an environment. Because the mutability of any aquatic environment occurred according to space and time the interaction of the surrounding , which may effect the biochemical properties of that environment. In reality, the water quality in such environment changes at least three to four times during the flooding period of four month due to the biochemical mutation. In accordance to biological theory some aquatic animals (reptiles or amphibians and a little air breather species) can resist in acidic or nitrogen water with its fast adaptation but some other (mainly fish species) are not, so these latter used to evacuate themselves to the better place for survival. The only one choice of evacuation of these latter animals is the waterways that they used to displace to other habitat for saving lives. This means that not all ecosystems or habitats its change its environmental properties at the same time and same level because the property composition is different from one to another habitat.

The displacement of fish is also difference from species, some make short evacuation then return back to the same habitat when the environmental condition changed to its tolerant fitness. However, some other species that are very sensitive to harsh environmental condition, they may take a trip to reach their satisfied niches. These displacements differ depend upon the nature of species and age especially the mutation of the surrounding environment . According to this natural phenomena the word migratory pattern of such species is hard to explain for almost all the fish species in the inland water of Cambodia. Even though, it seems that there Page 3 of 10

may have at least some of the freshwater species in any specific environment can be possible explained their migratory pattern by some empirical study.

In some logical truism the migratory of some freshwater fish species indicated the route to feeding grounds or spawning grounds of fry and adult fish certain period of time like Pangasidae species, except Pangasius krempfi (this species spawns in upstream of the Mekong River at the close to Laos spends it young age in the sea water unit it maturity stage) In this regard, my pragmatic empirical view cannot be accepted due to the pangasid fry is pushing downstream by the current of the Mekong River, by which some are strongly asorbed by the Tonle Sap River current (about 2-3 m/s during June-July) to the Tonle Sap Lake and some other are falling down toward the South China Sea by the Mekong downstream current (1.5-2 m/s during the same period) But these latter escaped from this untolerable environment by returning back to the better place in Cambodia, especially the Tonle Sap lake where they used to feed throughout the flooding period of the year.

Most large fish species including large and Cyprinid fish species evacuated themselves from the inundated forest to the open water of the Lake through deep waterways during August when water quality in theses habitats changed into acidic or nitrogen. Some predacious and carnivorous species returned back to the same habitat after sometime but large Pangasid and Cyprinid species used to continue to clean and high dissolved oxygen water in the river. Small sized fish enjoyed feeding in the flooding forest and the shallow open water. The latter group evacuated to the mainstream when the whole floodplain change its biochemical properties. Another group of fish species so called black fish such as snake head, working catfish Anabas, gouramy etc., which are more residential to such environment used to shift back and forth within the flooding forest and near by open water or stream. My empirical through our in different ecosystem in the Tonle Sap Lake and other wetlands through our the inland water system can be possibly explained as in the following Table. 2.1. Mutability of the Tonle Sap environment and organisms observed within the year

Biochemical condition Adaptation and Month Phenomena of water Effect to the fish species evacuation behavior of the species June Heavy rain caused Acidic water with high amonia Seriously kill all fish species No fish can resist in toxin flood water from the (NH ) content due to bacteria due to high toxin of amonia amonia so evacuation to watershed 3 except for the new flood water the non-toxic effect zone breakdown from anaerobic in the flood plain for survival and mainly for organism, except for area spawning effected by flood water extended in the flood plain July Flood water from the Acidic water cause by the Seriously effect to slow all slow adapted fish used Mekong River and decay of flooded grass and adapted fish species such as to evacuate to high D.O the watershed plan from the flood plain cyprinid sp area especially the flowing stream August Storm and cloudy Death plankton increased due Sensitively effect to large Large sized fish evacuated whether after short to less metabolism, which sized river fish such as to deep and clear water drought in the early caused turbulence and high Pangasidae sp., Cyprinid sp. bodies where D.O are high period of the month nitrogen water etc., September Heavy rain, storm and The primary production Most small fish, carnivorous Large sized fish crowded at cloudy whether increased in water in the and predacious species the mouth of the Tonle Sap occurred sometime flooding forest (high BOD) enjoyed feeding in flooding lake forest. October Heavy rain, storm. The decay vegetation and Water quality effect on small sized fish except for cloudy whether often death plankton created acidic sensitive and small fish but not black fish started to occurred and nitrogen water. so much on black fish evacuate from the flooding forest November Windy, cloudy sky Acidic and nitrogen water Water a quality effect all fishes Almost all fish including often occurred caused by death plankton and species especially black fish evacuated to decay vegetation due to black belodontichthys species. open water or waterways of metabolism where D.O are high December Windy, cloudy sky Acidic water with high amonia Serious effect to fish diseases Most Siluridae species are and cold whether concentration due to death and fish kills due to faster evacuated than the often occurred plankton and decay vegetation untolerable toxic water black fish species January Almost the same like Water are too shallow in the Still serious for the sensitive Almost all the slowly December but more flooding forest but the quality fish species not for adapted adapted fish species are sun shining turned little by little to normal species that permanently already evacuated to deep in the flooding forest inhabited channels or deep pools for long survival throughout dry season February Hot whether occurred Nitrogen water occurred at the Serious effect for all fish Almost all Cyprinid species shallow area species already left the flood plain and spent their lives in the deep rivers and waterways March Hot whether Water quality in almost all Fitness for almost all fish Most short-long evacuate increased deep waterways become species fish used deep pool as their Page 4 of 10

normal best shelter during dry season. Some species developed their gonad April More hot whether Most deep water bodies Fitness for almost all fish Most fish used to survive waterways are in good quality species around deep pools of the especially at the rapid system waterways and river. Most fish developed their gonad May Hot whether and Most water bodies are stable Fitness for almost all fish Mature fish search for some rain fall and remained good quality species spawning grounds.

3. The Importance of the Tonle Sap Lake Ecosystem Diversity

The quest for truth of what is the importance of the Tonle Sap Lake, in regard to the fisheries productivities, has become a critical issue for a long period of time. Logical answers have been made by a number of academician and scientists in the past time as well as the present time. But most of those are dogmatically based on a huge inundated forests around the lake body and its reserve water system between the lake and the Mekong River. However, no one empirical observation can be scientifically proved these correlation ship such as hydrological regime and the fish production, the fish production and the extend of inundated forest. Because empirical survey is incomplete to obtained a reliable fish production from the complexity of all fishing practice operating in this ecosystem.

My pragmatic preference to overcome this quest is to understand the complex natural function of all the components of the ecosystem and relationship among those by focusing on critical properties of the whole environment. Then study the physical structure support to ecosystem diversification to see the difference of ecosystem that help to classify the different characteristics of habitats of the Tonle Sap Lake environment. Table 3.1 below is the classification of habitat of the Tonle Sap Lake, which based on its differed physical and ecological properties (see figure 3.1.1)

Table 3.1 Classification of the natural habitat of the Great Lake

Defined Habitats Natural Conditions Ecological Support to fisheries

Great Lake Delta habitat (DH) The area where the Tonle Sap river splits It is a passage by which river fish fingerlings (Pangasid Tonle Sap river which extends into many channels before reaching the and cyprinid sp) from the rapid spawning ground in from Prek Kdam, Kandal Lake. These water channels are mainly upstream Mekong River, can enter the Great Lake province up to Snoc Tru, large and some of those are deep and wetland feeding during the flooding season. Most large Kampong Chhnang and Phat consisted of deep pools. There are many sized fish (maturity age) of Pangasid and Cyprinid Sanday. Kampong Thom seasonal flooded islands covered by gallery species used deepest channels to evacuate to the Mekong province at the mouth of the forests and flooded shrubs vegetation at the River during the peak flood peroid then followed by the Great Lake shoreline of the river, with marshes covered small fish. Some resident species such as Bagridae sp., by macrophytes and large silted swamps. Krytopterus sp. and other blach fish moved between the flooding forest and the water channels for spawning, feeding and sheltering. Great 's Eastern Swamp This is characterized by large swamps, Fish species are commonly diversified like in other habitat (ESH) Flooded area marshes, many shallow waterways and two regions of the Great Lake system but round fish (Channa entirely in Kampong Thom main streams: Stung Sen and Stung Stong sp.) are predominant. Other fish species such as Wallago province, which covers the originated from Dang Rek watershed. The sp., Krytopterus sp., Cirrhinus sp. Bagridae sp., and whole Tonle Chmar area, majority of the floodplain terrain is covered small sized Cyrinidae are also important. These fish are which extends from the Siem by gallery forests, grass and macrophytes, moving back and forth between flood forest and the open Reap and Kampong Thom and dense shrubland vegetation in the water, especially the Tonle Sap Lake, except for most of border down to Stung Sen shallow areas that some are dried up during Cyprinid sp. are used to evacuate to the main stream stream. the dry season during water retreated from the flood plain. Resident fish use this habitat as spawning grounds, feeding grounds and shelter during dry season. Great Lake's Northern Slope This floodplain terrain is mainly covered by Fish species are similarly diversified as in the whole habitat (NSH) Flooded area flooding shrubland, which dried up for 3-4 Tonle Sap Lake region but black fish are predominant almost all the lake .It is months in dry season. Tall trees from the especially Channa sp. and Trichogaster sp (moonlight entirely located in Siem Reap gallery forest are found only at the Goramy). White fish such as Cyprinidae, Noptotrus, province (extended from shoreline of the lake and deep waterways Schilbeidae and Bagridae sp. are fairly abundant. The Kampong Khleang stream to (Kampong Khleang stream). So large latter species used the open water of the Tonle sap Lake Siem Reap stream. flooded forest area in this habitat were for sheltering during dry season because there are very cleared up for agriculture purpose since fitness less water bodies for fish during dry season. The many decades ago. Most waterways within above species especially snake head fish, moonlight this system are shallow and fried up during gouramy and small cyprinidae used this habitat for peak hot season, which make this habitat spawning, feeding flooding season. Butmost spawners less importance. mainly come from the lake and near by wetlands. Fingerling of large Pangasidae and Cyprinidae sp. from the Mekong upstream are also found in this poor Page 5 of 10

ecosystem during the wet season. Great Lake's Western Swamp This is characterized by swamps and Black fishes (Channa sp., Trichogaster sp., Clarias sp., habitat (WSH) Flooded area mashes with complex deep waterways. The Anabas sp.,) are the dominant species in this species in which covers the northwestern general bottom feature of these channels this specific sub-system. Cyprinidae, Bagridae, margin of the lake from the are flat and retained water between 2.5 to 5 Krytopterus, Nopototerus, Pangasidae sp. are fairly / Siem Reap meters during dry season. The overall abundant. All fish species are faster evacuated to the province border down to Kbal wetland terrain is covered by dense gallery deep waterways within the system or to open water of the Taol Battambang/Pursat forest and grass mixed with thick flooded lake if the water quality in the flooding forest changed province border. shrubland vegetation. This flood forest then after sometime moved back to the same habitat forms a great nesting habitat and feeding when the quality of water turned to normal condition. groud for water bird species during the dry Large sized Cyprinidae and Pangasidae sp. left the season. But several thousand hectare of flooding forest to theopen water of the lake very early these forest especially the area close to the then proceeded the main stream and river. Small sized town have been converted into sisal Cyprinidae sp. used nearly streams where disolved plantation and rice fields. oxygen are high enough for them to survive hen harsh environment in the flooding forest occurred. Other species are not so important. Usually, black fish species are adaptive to this ecosystem as they spent their lives throughout the year between the flooding forest the waterways and the open water of the lakes within the system. Great Lake's Southern Slope This floodplain terrain is mainly covered by white fish species are fairly prevalent in this region habitat (SSH) Area which shrubland vegetation and some tall trees of because of its environment not fits enough to black fish. covers most to the western the gallery forest, which grow at the Even though Channa sp. is still abundant. The depth of wetland margin of the lake in shoreline of the lake and next to the Pursat stream created a great habitat of Krytopterus and Pursat and Kampong Chhnang waterways. Almostal waterways streams. Noptoterus sp. during dry season. Fish movements provinces, which extended But that stream was disturbed by many during flooding season are not much different from other from Kbal Toal. Battambang/ dams. The overall forest structure is habitats around the Tonle Sap Lake. As there are not Pursat border donw to the secondary due to frequent slashing and many water bodies located in this habitat, most fish Snoc Tru stream of Kampong burning for agriculture and domestic fuel species are sensitively displaced to open water of the Chhnang province. purposes. Tonle Sap Lake at the early stage of receding water from the flooding areas. All resident fish used this wetland for pawning and feeding during monsoon. Great Lake's Reservoir Habitat The central area where a large water body It is natural reservoir where most fish from the different (RH). Area varying in size retained year round sub systems of the lake, especially the latter three, from 2,300 to 3,000sqkm, temporarily inhabit during the dry season. Usually, fish which extends about 120km in the open water of the Tonle Sap Lake have less feed from South to North and is throughout the dry season. Most large sized Cyprinidae located in the northwestern and Pangasidae left the Tonle Sap Lake toward the part of the country. Mekong River through the deep water channels at the beginning of the retreated water phenomena. Theses fish used deep pools for sheltering during dry season.

The above characteristics of natural condition in relation to the biological aspect of the fish species show that the wetland consisting of numerous deep waterways are the critical ecological support to the survival and high productivities of the fish species.

4. Heuristic observation on the important role of the Tonle Sap and Mekong corridor

Maurice Blanc, 1958, wrote about the tremendous contribution of a Mekong Catfish species, which shared 30% of the total annual catch during the period of this study in the Tonle Sap Lake and other wetlands within the Mekong River system in Cambodia. This had stimulated my surge of understanding since 1981 on this productive species, Pangasionodon hypophthalmus, in the Mekong River that finally allows me to grasp more knowledge on the critical natural phenomena, which created a number of relationship on logic of the importance role the Tonle Sap and Mekong corridor in relation to the fisheries productivities in the Tonle Sap Lake region.

In 1981, 1982, 1983 and 1984 I started to observed the fishing activities and the species composition caught by the fishing lot # 4,6,9 (ex. #10), 12 (ex. #16), 16 (ex. #19) of Kampong Chhang province covering of the Tonle Sap Lake region. In 1984, 1985, I had continued to observed the seine fishing activities operated by the Vietnamese fishermen in the Dey Roneath/ Reang Til and Kampong Kuong, western and eastern Tonle Sap Lake, Concomittant to these above period, I did observe the fishing activities and the species composition of the bag net fishing lot row # 21 Peam Long Vek (presently abolished), row # 16, row # 10, 9, 8, 6, 5 and 2. From 1986 up to 1991, these fishing activities had been reviewed once again to justified that the movement of fish changed or remained stable. Within the above period 1981-1991, the movement of fish remained the same condition but catch of large sized fish were gradually declined.

These observation provided an understanding on time and the water channels where different fish species and sized used to evacuate from one niche to another for survival and existence. Large size fish (Pangasidae and Cyprinidae) were very sensitive to ecological properties of the habitat change. So they left the flooding forest Page 6 of 10

very early by mid of August. Late of September these large fish species exit the Tonle Sap Lake through two deep waterways: Prek Ta Pich, and Trek Ta Mem streams and some passed by Prek Dang Korm stream not Prek Ta Som as many of our fisheries officers expected even the at the entrance is 15m but it end only 9.5-10m (the latter observation made by using fish tester/ecosounder during late of September and October). The stream floor of Prek Ta Pich and Prek Dang Korm stream are flar, but Prek Ta Mem stream floor has many pools, which one is very deep about 24 meters during the observed period.

These fishes moved further downstream through Prek Ta Pang, Prek Ku, Prek Phlov Tuk, Prek Pralay Meas, Prek Stung Chruov, Prek Anlong Tunlea, Prek Ksach Spey, Tonle Koh Bay, Tonle Chroy Boboss, Tonle Chralay, Tonle bangkang Vea and Tonle Peam Long Vek Krao before entering the Tonle Sap River. The flor of these waterways consisted of a number of deep pool. The position, length and average depth of these waterways corridors are listed in Table Below.

Table 4.1 List of the waterways at the Tonle Sap Delta region where large sized fish species used evacuate from the Tonle Sap Lake (observed during September-October)

Name of waterways Position Length Average depth Other observation Prek Ta Pich N 12 0 31 ' 32.4 " 3.5km 10 -12.5m no pool E 104 0 25 ' 14.4 " Prek Ta Mem N 12 0 32 ' 54.0 " 4km 12 -15m deepest pool 25m E 104 0 25 ' 28.8 " Prek Dong Korm N 12 0 31 ' 32.5 4.5km 11 -13m deepest pool 17m " E 104 0 25 ' 13.5 " Prek Ta Pang N 12 0 32 ' 12.6 " 5km 10-12.5m deep pool 16m E 104 0 30 ' 56.6 " Prek Ku N 12 0 24 ' 21.3 " 10km 11 -13m deep pool 18m E 104 0 38 ' 02.7 " Prek Phlov Tuk N 12 0 28 ' 23.2 " 16km 12 -15m several pools 17 - E 104 0 37 ' 21.4 " 19m Prek Pralay Meas N 12 0 21 ' 35.8 " 13km 13 -15m deepest pool 25m E 104 0 37 ' 33.7 " Prek Stung Chruov N 12 0 23 ' 10.4 " 15km 14 -16m deepest pool 21m E 104 0 36 ' 42.6 " Prek Anlong Tunlea N 12 0 21 ' 35.8 " 6.5km 12 -14m deep pool 19m E 104 0 37 ' 33.7 " Prek Ksach Spay N 12 0 22 ' 52.7 " 6km 10 -12m deep pool 17m E 104 0 38 ' 24.6 " Tonle Koh Bay Kream N 12 0 30 ' 21.7 " 10km 11 -12m no pool E 104 0 30 ' 05.6 " Tonle Chroy Boboss N 12 0 16 ' 14.4 " 7.5km 11 -13m many pool and the E 104 0 41 ' 23.2 " deepest is 28m Tonle Chralay N 12 0 11 ' 6.5km 14 -15m many deep pool and E 104 0 48 ' the is 23m Tonle Bangkang Vea N 12 0 7 ' 3km 11 -13m One deep pool is E 104 0 48 ' 19m Tonle Peam Long Vek N 12 0 0 ' 18km 12 -13m Deep pool is Krao E 104 0 48 ' averaged 16m Tonle Sap River N 11 0 53 ' 41km 14 -17m Deepest pool is 23m E 104 0 47 ' located at the 7km last end of the river where the water channel becomes very narrow before reaching the Page 7 of 10

confluence Chaktomuk. Tonle Chaktomuk N 11 0 34 ' 2km 15 -17m E 104 0 56 ' Note: The position of each of the waterway corridor listed in Table above is represented the position at its entrance.

However, a huge amount of small Cyprinid species, which lately evacuated from the flood plain are not required any species any specific waterway corridors since these latter groups are distributed in all waterways. So the important role of the deep waterway corridors and deep pool are much are much more related to the large sized fish movement rather than small sized fish.

Large sized fish species, especially Pangasidae and Cyprinidae spend sometime from one to another pool along the corridor until they reach the Mekong River at the Quatre-bras (Chaktomuk), where some (usually, fatty fish) move upstream against the river current and some other (less fatty fish) move downstream to the Vietnamese water. The former group especially Pangasionodon hypophthalmus (weighed 10-15kg) are caught by the hook line early October when flood recession of the Mekong upstream started. The latter group especially Pangasionodon hypophthalmus (weighed 2-5kg) are caught by the gill net sometime later when they return from the Vietnamese water. According to these observations, even some are already passed the quatre-bras then turn upstream or downstream in October, but some other fish are still in the waterways corridor between the Tonle Sap lake and the quatre-bras. This means that fish are not really migrated, but just searching for better niche for survival.

In regard to fish movement occurring during dry season and the spawning behavior of all riverine fis species (Pangasidae and Cyprinidae), the Mekong River with its large deep pool (ranging from 17 to 78k depth) has played a very important role as a critical corridor for riverine fish to take shelter and reach its spawning grounds in the rapid system in Kratie, Stung Treng and Rattanakiri provinces.

Biologically, riverine fish species are not taking care the babies, so hatchlings of all species flow downstream by the current and most them enter the Tonle Sap lake by the Tonle Sap River wetland along side the river. The rest flow down by the current toward the South China Sea. The latter group grow up to the fingerling stage before they the estuary, thus they may escape from harsh environment and find the better place for survival. Table 4.2 below shows a list of the deep pool along the Mekong River that are critical to the existence diversification of the revering fish species.

Table 4.2 List of deep pool along the Mekong River detected during last dry season (survey May 2000)

Pool name Position Depth Other information Kratie province Koh Presng pool N 11 36 ' 28 " 8.2m Small pool, which host mainly E 104 55 ' 24 " Krytopterus sp. Preah Pralech pool N 12 55 ' 37 " 36 -41m Large pool, which host mainly Cyprinid E 106 10 ' 02 " sp. Sar Kang Keb pool N 12 57 ' 054 " 24m Small pool, which host mainly Cyprinid E 106 01 ' 08 " sp. Ve Val pool N 12 59 ' 46 " 20m Small pool, which host mainly Cyprinid E 106 01 ' 56 " sp. Kuol Runteas pool N 13 01 '05 " 26-30m Medium pool, which host mainly E 106 02 ' 10 " Pangasid and Cyprinid sp. koh Knhe Sre Koki N 13 06 ' 13 " 32m Very large pool, which host mainly big E 106 03 ' 02 " fish such as Pangasionodon gigas, Phypophthalmus, Pangasius sanitwongsei catlocarpio siamensis, Cirrhinus microlepis, Probarbus Julieni, Cyclocheiilichthys sp. Hypsibarbus sp., Wallago leeri, Krytopterus sp. etc Kandor Muoy Roy pool N 13 08 ' 06 " 18 -22m Large pool, which host mainly Pangasid E 106 01 ' 44 " and Cyprinid sp. Page 8 of 10

Pra pool N 13 02 ' 12 " 78m Deepest pool in the mainstream E 105 59 ' 44" Mekong River, which host large Pangasid and Cyprinid sp. Kbal Prek pool N 13 00 ' 27 " 8-21m Medium pool, which host Pangasid and E 105 58 ' 08" Cyprinid sp. Preah Twea Lech pool N 12 57 ' 46" 20m Medium pool, which host mainly E 105 59 ' 10 " Cyprinid and wallago (leeri) sp. Prey Veng/Kandal provi Phum Boeung Phsot pool N 11 21 ' 00.2 " 9-10.5m Very large pool, which host mainly E 105 16 ' 06.4 " Cyprinid sp. Neak Loeung Fisheries N 11 16 ' 11.3" 15 -16m Small pool, which host mainly Cyprinid quarter pool E 105 16 ' 56.2 " sp. Ang Ko pool N 11 17 ' 36.0 " 10 -26m Medium pool, which host Cyprinid and E 105 16 ' 50.0 " krytopterus sp. Neak Loeung ferry pool N 11 15 ' 42.1 " 17 -19.5m Large pool disturbed by the passage of E 105 16 ' 44.2 " the ferry and heavy navigation Prek Thom pool N 11 14 ' 12.8 " 20 -24m Large pool, which mainly host E 105 16' 32.7 " Pangasid, Cyprinid sp. Kor Dorb pool N 11 07 ' 35.4 " 30 -40m Large pool, which mainly host E 105 13 ' 55.4 " Pangasid, Cyprinid sp. Peam Chor pool N 11 07 ' 03.0 " 16-38.5m Very large pool, which hosts Pangasid, E 105 13 ' 30.8 " Cyprinid sp. Koh Nhek pool N 11 04 ' 10.3 " 11 -13.5m Small pool, which hosts cyprinid, E 105 12 ' 42.0 " Krytopterus sp.

5.Diversification of fish species and its genetic population in relation to the reverse water system between the Tonle Sap Lake and the Mekong River

In the fishes of the Cambodia Mekong, Rain both had defined about 500 species in 1996. The same author expected that there should have more if combining with different watershed system throughout the country. However, pragmatic observation on species diversity and genetic population of fish found less than what the above book claimed. This may because of some less populated species are of less interest by fishermen or observers.

Among the species that often occurred in catch throughout the country's freshwater system, three group of fish can be characterized as follow: • The black fish such as Channa sp., Thrichogaster sp., Clarias sp., Anabas sp. etc using flooding habitat for survival and reproduction. The two former species are the most populated species due to its mutation with their residence environment.

• The white fish or river fish such as Cyprinid, Pangasid, Krytopterus, Noptoterus, Bagridae etc. using flood plain for feeding and spawning but also relied on the waterways and the main river for evacuation. This group consists of many dozen species, which some large sized individuals are sensitive to the change of ecological properties of the environment. This group is the most prolific and reproductive species, which abundantly present in catches.

• The endemic species or species, which are localized in specific environment. In the Cambodian freshwater system, the rapid from Sambor, Kratie up to Cambodian Lao boder is the specific habiata for endemic species such as Chitala blanci, Chitala lopis, Bangana behri, Barbichthys sp., Gara sp., Mekongina erythrospila (a migratory species within Tonle Sre Pork, Tonle Sekong, and the Mekong upstream) etc. These group are not abundant due to its selected habitats for surviving an reproduction. At the present day, most large sized fishes have decline drastically, according to the MRC-fisheries project, small sized fish prevail the catch (70-80%). Comparing blanc report (1958) and the present day catch, Pangasionodon hypophtalmus has only 3% instead of 30% of the total production in the past, so is it assumed as under Page 9 of 10

threat.

6. The commercial fisheries activities and the logical argument of fish decline

For more than 140 years of industrialization the inland fisheries in Cambodia, especially in the Tonle Sap Lake, this programme has slightly contributed to socio-economics as it may safely be said that " non development of real benefit to local people were carried out during the above period ". But the French colonial minister stated in 1917 that the economic benefit of the colonization were marginal (Martin, 1994: 9). These statement contradicted to the objective of the inland fisheries industrialization programme in the past and the present government policy as well. However, wild fish in this productive fishing ground is going to decline gradually from time to time that raise a thousand concerns about the future of this resources and its habitats.

I can sum up theses concerns into two aspects: Over fished (1) and habitats deterioration (2) that and required to have a logical or scientific explanation. Reason in the past wad restricted and regulated fishing can avoid the problem of over fishing and habitat deterioration. These were stipulated in the fisheries law in the past and at the present time as well. But the decline of fish cannot be alleviated due to the bias of thought on the benefit of the commercial fisheries. Recently, a number of scientific research and study relating to these above two aspects has been conducted to find the best solution to help alleviate this resource from human pressures, but the results cannot be solved the problem.

My empirical observation can proved that all the fishing lot operation are cutting off the waterways within the wetland systems and the corridor connect that system to another. So a very few fish can be possibly escaped for survival and reproduction. Another test throughout a number of fish sanctuary had indicated that there are very few fish sheltering due to shallow water, except the area where there are brush park. But these latter are exploited illegally. My logical argument for fish decline is that the establishment of the commercial fishing lot are cutting off the waterways and river corridor where the fish used to evacuate for survival and reproduction within its life cycle. The bag net fishing along the Tonle Sap river especially, the narrow channels from the brewery factory in Russey Keo district down to the Quarter-bras (about 7km distance), which normally catch a lot of large sized fish (Pangasionodon gigas and hypophthalmus, Catlocarpio and other Cyprinid species) in October and November. Therefore restriction and regulation the fisheries cannot help to sustain this resource.

7. Conclusion

7.1. The biodiversity richness of the Tonle Sap Lake is characterized by the diversification of the ecological properties, which possessed a number of deep waterways where living organism used to evacuate when the local environment change.

7.2. Due to the fish empirical theory, the Tonle Sap lake can be classified into 6 sub-ecosystems.

7.3. Species diversity and genetic population diversity can be characterized by the diversification of the ecological properties of an environment and its connection to other environment by the critical water channel corridor where a number of sensitive species used to evacuate to the better niche they can breed and survive.

7.4. The decline of wild fish is the consequences of fishing lot operation, which usually block all the deep waterways and deep river channel corridor for commercial purpose.

7.5. All the fish sanctuaries defined by the fisheries law are located in the open and shallow waters which are fitness less to all species.

8. Recommendations for sustaining the fisheries resources through critical waterways corridor protection

8.1. Abolish all the fishing lost and open access to mobile fishing operation that are not harm to the environment and biodiversity

8.2. Abolish some fishing lot located on the important water channel corridor such as fishing lot #2, Kampong Thom, Fishing lot #4 and 6, Kampong Chhnang province, Fishing lot #9, Kampong Chhnang province, Fishing lot #12 and 16 Kampong Chhnang province, bag net fishing lot located at the narrow part of the last end of the Tonle Sap River.

8.3. Keep all fishing lot but prohibited to block the whole waterways corridor (should be 1/3 or ½ cutting across the waterways corridor). Page 10 of 10

8.4. Review the suitability of the existing fish sanctuaries properties and its fitness to the fish.

8.5. Re-establish the fish sanctuaries on a few sites but large area by selecting the most critical fish habitat for conservation purpose (see Figure 8).