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Introduction
The caves of Thailand, like most caves around the world, are found in what geologists call limestone karst regions. An important feature of karst is that it contains extensive underground channels that carry water for great distances. Undisturbed karst systems supply pure waters for drinking and agriculture, and are a critical natural resource for many countries around the world.
Thailand has extensive karst regions and most of the country's water for human consumption passes through karst. Thus, the purity of karst water is an important concern in Thailand. Nevertheless, it is not a natural resource that can be taken for granted. Because water flows so freely through karst systems, water borne environmental pollutants such as pesticides and fertilizers can easily and quickly spread over wide areas. Therefore, even though most people never go inside caves, the "ecological health" of karst systems is important to everyone.
Many animal species live in caves and karst waters, and we can learn a great deal about the condition of karst systems by studying these hypogean [1] animals. Cave animals, especially troglobites , are more sensitive to deterioration of the environment than epigean animals. Because cave ecosystems depend upon the environment above ground for input of food and water, their "health" also provides good information about the state of the surface environment.
Cave ecosystems can serve as "early warning systems" for broad environmental problems. For example, deforestation increases water runoff and soil erosion. Evidence of significant erosion can be seen early in caves as an increase in silt deposition. As a second example, excessive use of agricultural chemicals and pesticides may poison the environment. Because troglobitic species are usually more sensitive to environmental change than epigean species, this effect can often be seen earlier in caves than above ground. Increased siltation and chemical loading are both expected to lead to local extinction of species and decreased species diversity.
Many cave animals, especially in the active stream caves of Thailand, are aquatic. Numerous species of aquatic invertebrates, including crayfish, amphipods, isopods, segmented worms and flatworms have been described from Thai caves and many more remain to be discovered. Aquatic cave animals are, because of their close contact to karst water, most sensitive to deterioration in its quality. The largest of these animals and the ones that live in most intimate contact with the waters are the freshwater fishes.
Thailand has a rich freshwater cave fish fauna. Five species of troglobitic cave fishes have been described in the scientific literature, two more have been discovered but not yet described, and others remain to be found. Cave adapted fishes comprise a significant part of the vertebrate diversity of Thai caves and, indeed, the biodiversity of Thailand. They are important not only for what they can tell us about how animals survive and flourish in challenging environments, but also because they are sensitive indicators of environmental condition and provide useful information for cave management decisions.
Thailand's cave fishes are members of two families well represented in surface waters: the balitorid river loaches and the cyprinid minnows and barbs. Two species each are known from Kanchanaburi, Mae Hong Son, and near Phitsanulok, and one from near Khon Kaen. Five of the seven known species are river loaches, the other two are barbs. The most spectacular of these loach species is the waterfall climbing cave fish, Homaloptera thamicola.
Most of the caves of Thailand are still unexplored, and it is probable that many more species of cave fishes remain to be discovered. Because of their scientific interest and potential to provide information useful in cave management, discovery of new cave fishes is a priority of biospeleologists. In addition, it is important to understand the conditions which lead to the evolution of cave fishes.
Not all caves with water have cave fishes. In fact, only the minority do. For this reason, it is of scientific importance to ask why cave fishes are absent from some caves and present in others. What distinguishes the caves with cave fish from those lacking them? Is it the size of a cave system, or its isolation from surface waters, or some other feature? Alternatively, perhaps only chance events control the distribution of cave species.
The freshwater fishes of caves include cave adapted troglobitic species as well as epigean, surface fishes. In fact, the caves of Thailand contain more epigean fishes than true troglobites. One reason for this is that cave entrances in Thailand are often at river level. Therefore, surface fish can just swim in. If they find food, they can survive and stay.
In order to learn more about the freshwater cave fishes of Thailand, we surveyed eleven caves in March of 1998. Most of the caves we chose to explore had never been known to have troglobitic cave fish. We chose these caves because of the possibility of making new discoveries of troglobites, but also because the epigean fishes of caves are also interesting.
The three most common families of freshwater fishes in Thailand are the Cyprinidae (204 species of minnows and barbs), the Bailitoridae (62 species of river loaches), and the Cobitidae (31 species of loaches). These comprise 52% of the 570 species that have been recorded in Thailand [2]. Cyprinids are relatively tolerant of polluted waters, but cobitids and, especially, balitorids are not. Therefore, the presence or absence of these different epigean fishes in cave waters can provide information about water quality and purity.
We concentrated our efforts in Kanchanaburi and southern Tak provinces and on the Peninsula, near Phang Nga. Fishes were sampled with hand nets in order to examine them closely enough to identify them and were then released unharmed into the water. Because we did not make permanent collections, it was difficult to identify many of the specimens beyond family [3]
During the survey, we obtained evidence of decreased cave fish diversity in several caves that were near centers of human activity. Two of these caves (Tham Thapan and Tham Pung Chang) are located in the town of Phang Nga and are visited heavily by tourists. As the Table below shows, Balitorid and Cobitid loaches were absent from the caves with strong human presence (tourists, evidence of pollution, construction of dams, fishing, etc.). These two families of fish seem to be particularly sensitive indicators of environmental degradation. Our results cannot prove that human activity changed the fauna of these caves because we have no information on the original cave fauna, before the human impact. Nevertheless, the observation underscores the importance of obtaining baseline data on cave fauna so that future work will be able to detect environmental alterations.
| Cave Name | Cyprinidae | Siluridae | Sisoridae | Channidae | Cobitidae | Balitoridae | HUMAN PRESENCE |
| Tham Nam Phra Tat | + | + | - | - | |||
| Tham Nok Nang En | + | + | + | ||||
| Tham Yai | + | + | |||||
| Tham Sao Hin | + | ||||||
| Tham Kaew | + | - | ++ | ||||
| Tham Than Nam Lod Noi | + | ++ | |||||
| Tham Pung Chang | + | - | ++ | ||||
| Tham Phet | + | + | + | + | + | ||
| Tham Nam Tok | - | - | ++ | ||||
| Tham Nam 1 | + | + | + | + | + | ||
| Tham Thapan | + | + | + | - | ++ |
Interpretation of Symbols
P = Family representatives were found in the cave
no symbol = Family representatives were not found in the cave
- = were not found although searched for very carefully
+ = moderate human impact
++ = major human impact
Cave Survey
Caves Visited in Thailand, March 1998
EREWAN NATIONAL PARK: From 3 to 4 March, we stayed at the headquarters of Erewan National Park. We used this as a base camp to visit Tham Nam Phra Tat on 3 March 1998. The main passage of this cave is a stream gallery about 1.1 km in length. The cave entrance is at its resurgence and the upstream end is blocked by a waterfall. We looked for fishes during our visit there and searched thoroughly between the entrance and the waterfall. The cave stream has a variety of habitats, ranging from places where the water flows slowly over muddy or silty bottoms to riffly areas where the water flows quickly over rocks. We saw many individual fish in the cave, but we did not see any cave adapted fishes. We saw, but did not catch, cyprinids and sisorid catfish. The cyprinids were small (3.0 cm) and light in color, but had eyes. The catfish were quite common in the cave and ranged in size up to 15 or 20 cm in length.
We searched for balitorid river loaches in riffly areas, but saw none. We specifically looked for representatives of the genera Balitora, Homaloptera and Schistura, which are found in fast moving waters on the surface and in undisturbed caves throughout Thailand. Their absence may be evidence of human disturbance. The cave lacked significant internal tributaries and its waters did not appear to be isolated from those of the surface stream. These factors, as well as its small size, may explain the lack of troglobites.
Tham Nam Phra That was explored by the French in the 1980s and they reported that it contains an abundant cave fish fauna. We saw no evidence of blind cave fish, however. There are three possible explanations for the difference between the observations of the two groups:
1) We may have overlooked troglobites that were in the cave. Although this is possible, we consider it unlikely; the cave is not large and our search was thorough enough that we should have seen troglobitic fish, if they were present.
2) The cave may have contained troglobitic fish in the past but they may now be greatly reduced in numbers or extinct.
3) The French may have made an error. Epigean fishes living in caves often are light in color and, especially with catfish, they may have small eyes. Because the French cavers did not collect and preserve specimens, they may have mistaken epigean fish for troglobites.
LAM KHLONG NGU NATIONAL PARK: from 4 through 10 March we stayed at the headquarters and at the Khao Phra ranger station at Lam Khlong Ngu. The expedition benefited greatly from the hospitality and support of the chief of the park, Mr. Sarawut Meuanphra and his staff. Our thanks to them for helping to make our visit comfortable and productive.
The Lam Khlong Ngu system is over five kilometers in length and consists of a series of shorter caves separated by places called "karst windows" where the cave stream opens to the outside. During our visit, we surveyed the caves and surface waters at karst windows #4 (Tham Nok Nang En) and #6 (Tham Yai or "Big Cave"), and at the final downstream resurgence (Tham Nam Lot or Tham Sao Hin). We also explored a doline to the southeast of karst window #6 looking for new cave entrances. See maps of the Tham Nok Nang En system and the Swallows' Cave section (Map drawn by the DeHarveng team).
5 March
Karst window #4 and Tham Nok Nang En -- In the surface waters outside the cave we observed, but could not catch, small river loaches (nemacheilene fishes) about 3-4 cm in length and a catfish (genus Glyptothorax) about 20cm in length. We entered the cave at 3 p.m. and out at 7:30 p.m. In the cave we caught some small cyprinids in slow water and 4 small nemacheilenes in fast water. Upon closer inspection, the nemacheilenes proved to be Schistura jarutanini. These fish were extremely interesting to see because this is one of the species of cave fish known from the cave. Some individuals of this species do not have eyes and seem to be true troglobites while others have eyes and pigment and are typical epigean fishes. The ones we saw had eyes and pigment. We also saw some large cyprinids (25 - 30 cm)in fast water, but could not identify them.
6 March
Karst window # 6 and Tham Yai. Karst window # 6 is located just north of the Tham Yai ranger station at Lam Khlong Ngu NP. Outside the cave we observed Cyprinids (probably Danio sp) in slower moving water and Balitora sp (possibly B. burmanica) on the rocks in faster flowing areas. In Tham Yai, in the shallow quiet water, we saw cyprinids w/eyes and light in color. We netted several more epigean (with eyes) Schistura jarutanini (Balitoridae) on loose sand/silt bottom.
7 March
We explored a doline one km east of Tham Yai and find several sink holes. None of these sink holes leads to cave passage. One of them (labeled "CO2 hole" in Tham Nok Nang En system map) has high levels of carbon dioxide ("bad air"), as shown by the inability of a cigarette lighter flame to stay lit when lowered into it.
8 March
We visit and survey Tham Reua Hong ("Boat Cave") with measuring tapes, compass and inclinometer. Tham Reua Hong is located at coordinates 47P 0479131, 1638159. It has no water, but is a beautiful example of a coffin cave, with teak wood coffins and pottery near the entrance. Many small images of the Buddha are located near the entrance and at a point half way in. We surveyed the full length of the cave (140 meters total), including the last 60 meter section which has "bad air" (high levels of carbon dioxide).
9 March
We visit Tham Sao Hin (also called Tham Nam Lot and "Column Cave -- map drawn by the Australian expedition.). This is the reported locality for the troglobitic fish, Schistura jarutanini. Unfortunately we are unable to find any troglobitic individuals of this species. Because this is the most downstream resurgence of the Lam Khlong Ngu system, the cave contains much swiftly moving water. We see Schistura species in the waters outside the cave, but only some large dark cyprinids in the cave itself.
Our failure to find troglobitic S. jarutanini is more likely due to the large size of the cave and our not searching in the correct places. The water of the cave is fast running and seems pure and unpolluted. We are hopeful that future trips will lead to the rediscovery of this unusual species.
10 March
We travel to Sai Yok NP, to the south and visit Kaew Cave. This small cave provides access to stream passage at a lower level and is supposed to have another troglobitic fish, a species of cyprinid, not named in the literature. We see cyprinids, but they are epigean, light in color but pigmented and with eyes. It may be that an epigean cyprinid exists in the cave but has retreated deeper, beyond our search area. This could be because the cave is near the park headquarters and has many visitors. On the other hand, the original reports of a troglobitic cyprinid may have been in error, because even epigean fishes look light in color when they are found in caves.
11 March
We visit Tham Than Nam Lod Noi (Amphoe Sawi, Chumphol Province -- coordinates 47P 0494050, 1131317) and survey it roughly. This cave is much visited by tourists and probably receives considerably pollution from the nearby town. The water is cloudy and probably supports a high algal or bacterial growth derived from surface waters. We netted one fish in the cave which appeared to be a Channa lucius.
12 March
We visit Tham Pung Chang in Phang Nga town. This is a small through cave with 1.2 km of passage. There are some breakdown areas and two places with riffles and rapids caused by basalt dams intruding into the limestone. These riffly areas provide ideal habitat for Balitorid river loaches, and we look hard to find them, but none are to be seen. As in Tham Than Nam Lod Noi, we feel that the closeness of this cave to town, the considerable human presence, and high levels of water pollution have led to local extinction of balitorid species. We net a large cyprinid in the cave (Danio regina) and see other small cyprinids (Brachydanio kerri) outside the cave at its upstream entrance.
13 March
We head north of Phang Nga, past Thap Put town to Tham Phet. This cave is dammed at the downstream entrance and the first 150 - 200 meters of passage are clogged with mud. Upstream, this changes to gravel and rock. We were unable to penetrate beyond a 6 meter waterfall, about 600 meters upstream of the dammed entrance. We saw several different species of fishes in the cave. We saw, but could not catch a catfish (Family Siluridae). In addition, we netted three eel-like cobitids over mud (genus Lepidocephalichthys) and saw others. We netted four Small nemacheilenes (genus Homaloptera) clinging to rocks covered by a thin film of moving water. We also saw another Homaloptera in an area of rapids. We netted two Danio regina (Cyprinidae) in a pool with a silty muddy bottom. We also netted a crustacean crayfish Atyopsis molucaensis.
The overall impression of this cave was that the fish fauna was still quite rich and that the impact of human presence (the dam) had not yet affected the upstream end of the cave. Beyond the waterfall, the cave may be even more unspoiled.
15 March
We visited Tham Nam Tok in Amphoe Thap Put. This cave is also dammed at the downstream entrance. The dam has flooded the cave and completely altered the habitat. We swam in through three rooms for a total of about 170 meters until the passage sumped. In two places the cave had attractive decoration and must have been quite beautiful before its destruction.
We also visited Tham Nam 1 (French Expedition Cave Map). The fish fauna of this cave was relatively rich. We netted three Lepidocephalichthys (Cobitidae) on silty rocks, and saw two Danio regina (Cyprinidae) in deeper pools. In areas where there were rapids and waterfalls, we netted balitorid river loaches (four Schistura robertsi and five Homaloptera).
This very small cave (600 meters of passage) seems to support a varied fish fauna. We met and spoke with some local fishermen using nets inside the cave to catch cyprinids and catfish.
16 March
Finally, we visited Tham Thapan in Phang Nga town. The cave entrance is located at Wat Tham Thapan and is much visited and affected by tourists. We saw no Balitorid species in the cave. We netted two catfish (Silurichthys sp), three small Channa limbata (Channidae) and three Systomus sp (Cyprinidae).
Expedition Personnel
Leader: Nopparat Naksathit, Office of GIS, Natural Resources Conservation Office, RFD.
Others: Dean Smart, Natural Resources Conservation Office, RFD.
Chavalit Vidthayanon, Aquatic Natural Resources Museum, Department of Fisheries. Dr. Chavalit is one of the world's foremost authorities on the freshwater fishes of Thailand and Southeast Asia.
Richard Borowsky, Department of Biology, New York University, NYC, USA. Specialty in the population genetics of cave fishes. Published over forty scientific papers and articles on the population biology and ecology of freshwater fishes.
William Fanning, Marine Technical Division, University of Rhode Island, Narragansett, RI, USA. Dr. Fanning is an expert on marine biology and an experienced cave explorer.
Glossary
The terminology used to describe cave animals is complicated and the words used by one writer may have a different meaning when used by another. This short section is intended to introduce this terminology and define the words that are used for description in this report.
EPIGEAN means living on the surface of the earth. Because epigean fishes live in the open waters and experience the light of day, they have eyes and have pigmentation. All of the freshwater fishes that we see in rivers and streams and that we buy in the market place are epigean fishes.
There are three words that are used to describe animals found in caves: Hypogean, troglobite and troglomorph. These refer to where animals are found, whether they must live in caves and what they look like. The three terms overlap somewhat in meaning. Nevertheless, not all hypogean animals are troglobites and not all troglobites are troglomorphs.
HYPOGEAN means living underneath the surface of the earth. Usually, the term refers to populations that have lived in caves for many generations. Populations that have lived for many generations without light may be pale in color and have small eye size.
A TROGLOBITE is a cave dwelling animal that cannot survive outside caves. It must complete its life cycle in a cave environment. In general, when we say "cave animal" or "cave fish," we mean "troglobite."
A TROGLOMORPH is an animal whose ancestors have lived in caves long enough so that it has small or no eyes and reduced in pigmentation.
[1] See glossary section, above, for definitions.
[2] "Diversity of Freshwater Fishes in Thailand" by Chavalit Vidthayanon, Jaranthada Karnasuta and Jarujin Nabhitabhata, Royal Thai DOF, 1998 is the most up-to-date and authoritative checklist.
[3] One recommendation to the RFD is that small voucher collections be permitted in the future and archived at the Museum of the National Inland Fisheries Institute in Bangkok.
Webpage and authored links © 1998 Richard Borowsky, Department of Biology, New York University.
No reproduction of content without prior consent of the author.
