17. Family: Sciaenidae Boesemania microlepis According to the findings of the present survey, Boesemania microlepis is distributed from the Mekong delta to Xayabouri in the Lao PDR. However, the one report received from Xayabouri was the only one to mention the species upstream from Paksan in Boulikhamxay province, indicating that it is extremely rare along that stretch of the river. Other fishermen in the area reported that although the species could previously be found there, it has not been seen for many years.1 Although the map indicates that the species undertakes migrations, the movement appears to be sporadic and covers only a short distance. Above the Khone Falls, the migrations usually take place around the onset of rising water levels at the beginning of the flood season. Downstream movements above the Khone Falls were not reported. 1 Kongpeng Bouakhamvongsa, personal communication. Boesemania microlepiss Vientiane Khone Falls Phnom Penh Species reported Boesemania microlepis Vientiane Khone Falls Migration, October to February Phnom Penh Migration, May to September Migration, March to May Below the Khone Falls, these short-distance upstream movements are usually seen during receding water levels at the end of the flood season. Downstream movements occur during the period of rising water levels. The lunar cycle also appears to effect migration, i.e., three fishermen, all from the Kompong Cham to Kandal stretch, mentioned that the movements occur on, or just before, a full moon. Two fishermen, one from Xayaboury and one from Stung Treng, reported that the species migrates solitarily rather than in schools. One fisherman in Kompong Cham province stated that the fish migrate in order to follow their prey, which comprises small migrating fishes. Previous reports support this finding, although shrimps appear to be the main food source of this species (Rainboth, 1996, Baird and Phylavanh, 1999a and 1999b). Eggs were only observed between April and July (two reports in April, five in May, three in June and one in July), indicating that the peak spawning period is in May. Baird and Phylavanh (1999a) found that spawning occurs in deep water sections of the Mekong River during the height of the dry season between March and early May. Bardach (1959) suggested that the spawning period occurs during May-June in Cambodia. Boesemania microlepis has been reported to make loud croaking vocalisations during its spawning period (Baird and Phylavanh, 1999a). Based on the recording of the croaking, seven spawning grounds associated with deep pools in Khong district, just above the Khone Falls, were confirmed (Baird and Phylavanh, 1999a)..