According to the present survey, the distribution range for Pangasius conchophilus is from the Mekong delta along the Mekong River to Chiang Saen, near the border between Thailand, the Lao PDR and Myanmar.

Between March and August, Pangasius conchophilus migrates upstream from Khong Island, just upstream of the Khone Falls, to the northernmost station at Chiang Saen. All surveyed stations along that stretch reported this movement, which appears to constitute two separate migrations: (a) a non-spawning (trophic?) migration from March to May, comprising sub-adults within the size range of 10 to 40 cm; and (b) a spawning migration from May to August, comprising fish of sizes 40 to 90 cm.

Along that stretch, eggs were reported from May to August, with a strong peak in June-July. Juveniles of 4 cm were reported at two Thai stations, one at Klong Kaem district, Ubon Ratchatani province, and one at That Phanom district, Nakhon Phanom province.

From the Khone Falls to Kandal, near Phnom Penh, eggs were observed between March and August (12 reports), with a peak during May-June (9 reports). At that time, the fish are migrating downstream (reported by all 13 Cambodian stations). Juveniles (young-of-the-year) were also reported at several places along this stretch. For example, at Kratie and Kandal, fish of 2 cm were observed during June-August and July-August, respectively. At both places, they appear in peaks of 3-5 days, which corresponds with a spawning time around May to June and would indicate that spawning occurs somewhere upstream between Kratie and the Khone Falls, or in the Sesan tributary system.

In the Mekong delta, mainly juveniles were reported. Almost all stations reported fish smaller than 30 cm. Only one station (Hong Ngu, Dong Thap province) reported fish of up to 90 cm and weighing up to 35 kg, which may indicate misidentification. Since Pangasius conchophilus is not believed to reach such sizes, further verification is needed. Also in the Mekong delta, 2 cm juveniles appear in June (e.g., Thot Not, Can Tho province; Hong Ngu, Dong Thap province). At the end of the year they have grown to about 20 cm.

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