Studied sites and data collection

This study was conducted in the Ping - Wang river basin, located in upper Chao Phraya river basin (the largest river of Thailand). The Ping basin is one of the largest drainage basins of the Chao Phraya river basin with a total length of 658 km and draining 33,896 km and extends to 44,688 km if included the Wang river basin. The Wang river is 440 km long and has a catchment area 10,791 km2 (Takeuchi et al., 2005). The Wang river flows southwestward to join the lowland of Ping river in Tak province and they combine to form a large watershed area between 15q42’ and 19q48’ North and 98q04’ and 100q08’ East. The highest altitude of the sampling sites in this thesis is at 1,700 m ASL and connected to the lower Chao Phraya river basin at the altitude of 40 m ASL.

Table 2 Descriptions of the sub-basins in the Ping-Wang River Basin and sampling protocols Sub-basin Geographic Coordinate Bottom types Elevation (m ASL) Distance from the sea (km) Water depth (m) Stream width (m) Collecting period Upping Ping (UP) 19°07’-19°48’ N 98°47’-99°17’ E G, P, R, S 684 r 228.3 1,026 r 24.1 0.4 r 0.2 7 r 0.5 2008 Maetang (MT) 19°10’-19°45’ N 98°27’-98°55’ E G, P, R, S 756 r 166.2 1,067 r 36.0 0.6 r 0.4 13 r 11.2 2000-2001 2003-2004 The second Ping

(SP) 18°31’-19°33’ N 98°24’-99°22’ E G, P, R, S 553 r 160.2 982 r 41.0 1.9 r 6.0 74 r 230.5 1996, 2003-2004, 2008 Maeklang (MK) 18°24’-18°35’ N 98°28’-98°41’ E G, P, R, S 1,070 r 213.4 877 r 4.6 0.3 r 0 11 r 5.4 2008 Maecheam (MC) 17°57’-19°09’ N 98°04’-98°37’ E G, P, R, S 627 r 207.3 927 r 53.9 0.7 r 0.4 21 r 17.4 2007-2008 The third Ping

(TP) 17°48’-18°43’ N 98°14’-98°44’ E G, S, M 261 r 11.5 704 r 43.8 2.8 r 1.2 424 r 224.6 2005-2006, 2009 Maeteon (ME) 17°13’-18°02’ N 98°14’-98°34’ E G, P, R, S 804 r 229.2 847 r 43.0 0.5 r 0.2 8 r 3.8 2008 The forth Ping

(FP) 15°50’-17°49’ N 98°39’-100°02’ E G, S, M 120 r 33.5 580 r 68.4 2.7 r 0.5 359r77.5 2009 Lower Ping (LP) 15°42’-16°10’ N 99°27’-100°08’ E G, S, M 48 r 8.0 425 r 16.0 3.2 r 1.3 258 r 27.7 2009 Wang river (WA) 17°07’-19°24’ N 99°00’-100°06’ E G, S, M 408 r 123.8 833 r 225.2 0.9 r 0.9 28 r 48.2 2009 Note Bottom types: R = Rocky, G = Gravel, P = Pebble, S = Sandy, M = Muddy

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The collection of fishes and environmental variables for P1 and P4 was conducted in the mainstem of Ping and Wang rivers as well as their asscociated tributaries. Various habitats found in the studied area are presented in Figure 4. There were a total of 272 sampling sites from 10 sub-basins (Fig. 5A) viz., upper Ping (UP), Maetang (MT), the second Ping (SP), Maeklang (MK), Maecheam (MC), the third Ping (TP), Maeteon (ME), the forth Ping (FP), lower Ping (LP), and Wang river (WA). The locations and fundamental geographical characteristics of each sub-basin are provided in Table 2.

Figure 4 Various freshwater ecosystems found in Ping-Wang River basin. A: Waterfall and mountainous habitats, B: Shooting flow stream in first order stream, C: Secondary order stream with rock and gravel bed was located in mountainous stream, D: Secondary order stream with sandy bottom was located in lowland area, E: River mainstream located in lower part of Ping- Wang rivers and F: Reservoir

Note: Habitats A, B, C, D, and E were sampling area for P1 and P4; meanwhile data for P2 and P5 was from the reservoir. Habitats A and B were also the sampling area of P5.

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Figure 5 Maps of the studied area; A: The Ping-Wang basin and its sub-basins (P1 and P4), B: the Mae-ngad reservoir (P2 and P5), and C: Maecheam stream and the sampling sites (P3)

Note: (a) abbreviations for the sub-basins: UP=upper Ping, MT=Maetang, SP=second Ping, MK=Meklang, MC=Maechaem, TP=the third Ping, ME=Maeteon, FP=the fourth Ping, LP=lower Ping, and WA=Wang river

(b) abbreviations for the sampling sites in the Maengad reservoir: K= Huay Mekhod, P = Huay Mepang, S = Huay Mesoon, T = Huay Tontong, M = Huay Mekua, H = Huay Phakub, J = Huay Mejog, W = Huay Panwa, C = Huay Chompoo, L = lower part of the reservoir, U = upper part of the reservoir.

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P2 and P5 were focused on the Mae-ngad reservoir, a small high land reservoir of upper Ping river in Chiangmai province (19º15.18 N, 099º 03.35 E to 19º 15.25 N, 099º 17.43 E, Fig. 5b). The dam is multi-purposes as hydropower and irrigation, and fisheries is a secondary benefit. Its elevation ranges from 412 to 425 m ASL with a catchment area of 1,309 km2, a water surface of 16 km2 and it can store water up to 265 million m3. It is dammed across the Mae-ngad stream, one of the first order stream tributaries of the Ping river basin. The maximum depth of the reservoir area is 30 m with a mixed clay and silt bottom. Meanwhile, the depth of the tributary streams, connected to the reservoir, ranges between 0.25-2.0 m and there are various bottom types (i.e. rock, gravel, sand, silt and mud) along the stream gradient.

Fifteen sampling sites in the mountainous area of Maecheam first order stream (Fig. 5C) were selected for P3 to collect Oreoglanis siamensis. Maecheam stream locates in the west wing of Ping river and lies between 282 and 2,565 m from ASL. It is a major upper tributary sub-basin of the Ping river, which locates 117 km South-West from Chiangmai city. The Maechaem sub-basin is bounded by coordinates 18° 06’ - 19°10’ N and 98°04’ - 98°34’ E, and includes a total area of 3,853 km2. The climate of this mountainous basin is defined by large variations in seasonal and annual rainfall that are influenced by Pacific-born typhoons, superimposed on the south-west monsoon (Walker, 2002). The orographic effect induces an altitudinal increase of spatial rainfall distribution (Dairaku et al., 2000; Kuraji et al., 2001). The average annual temperature ranges from 20 to 34°C and the rainy season is from May to October.