Mekongina erythrospila is a cyprinid species endemic to the Mekong Basin. Some fishermen complained about the quality of the flipchart picture of this species, and misidentification by some fishermen may have occurred.

Fishermen from Chiang Saen district in northern Thailand and downstream to Pak Lay (Lao PDR) identified this species. There were no reports of the species from Chiang Khan in Thailand to Paksan in the Lao PDR. Mekongina erythrospila was, however, identified at all three stations in Thakhek, the Lao PDR. It was not noted at Tad Phanom or the northernmost station in Mukdahan (both in Thailand).

Fishermen between the downstream station in Mukdahan to Sambor (Cambodia), were familiar with the fish. South of Sambor, only fishermen at the Ap Tan My and Phu Hiep stations (Viet Nam) identified the species; however, those reports were probably due to misidentification and thus need verification. A southern distribution limit at Sambor coincided with earlier reports by Roberts and Warren (1994). One fisherman at Klong Kaem in Thailand mentioned that the species never migrates into small streams. It was also recorded at Xe Bangfai, Nam Theun (Kottelat, 1998) and Xe Done (Noraseng et al., undated). Rainboth (1996) also stated that the species only inhabits medium and large-sized rivers.

It is interesting to observe that in Stung Treng, Cambodia, near the Lao border this species is called by its Laotian name (Trey Pa Sa-ee). Further south, in Kratie, fishermen were unable to identify it by name although they recognised the fish, indicating that the species was rarer in that area. The distribution pattern indicates that the species prefers rocky stretches with rapids and a fast current, and concurs with observations by Rainboth (1996).

The maximum weight of fish reported during the survey was 3 kg in Mukdahan district and 2 kg in Chiang Saen district of Thailand. The two reports were almost certainly based on misidentification, since fishermen at the remaining stations reported a maximum size of about 40 cm or weight of up to 1 kg. Rainboth (1996) mentioned 45 cm as the maximum length for the species. In a survey in southern Lao PDR, Baird (1998) reported the largest individual as weighing 1.2 kg.

Mekongina erythrospila was reported to migrate upstream from Pak Lay to Chiang Khong between March and May. Many Lao fishermen in that area reported that the migrations start when the first heavy rains of the monsoon season occur, or when the river water change from being relatively clear to a reddish or brown colour. Only one report of downstream migration from Pak Lay was received from fishermen who observed Mekongina erythrospila migrating downstream in October-November.

From Klong Kaem to Mukdahan in Thailand, M. erythrospila migrates upstream from February to April; however, none of the fishermen at those stations knew about downstream migrations. Noraseng et al. (undated) reported upstream migrations in the Xe Done River between December and March. South of the Khone Falls, upstream migrations were generally reported to occur from November to February, while downstream migrations occur from April to June. One Thai fisherman mentioned that Mekongina erythrospila has black fins when it migrates downstream.

Mekongina erythrospila migrates in big schools comprising several hundred fish, often together with other cyprinids and loaches such as Hypsibarbus spp., Scaphognathops spp., Henicorhynchus siamensis and Botia modesta. One Thai fisherman reported that the juveniles are also migratory.

Few fishermen were able to give any detailed information about the reproduction habits of this species. One fisherman from Xayaboury, Lao PDR, reported seeing eggs in the abdomen of the fish during May and June. In Stung Treng and Kratie provinces, some fishermen said they had observed eggs from January to June, with most observations occurring in June. Those observations are consistent with a spawning time from June to August as reported by Noraseng et al. (undated).

The smallest juveniles, around 6 cm, were reported from the southern areas in Khammouan, Ubon Ratchathani, Champassak and Stung Treng provinces. One fisherman at Kemmaratch, Thailand, explained that he caught juveniles in the mouth of a stream and stocked a pond with them.

Hypothesis:
Two main populations of Mekongina erythrospila exist in the Mekong mainstream. A northern population occurs between Pak Lay and Chiang Khong, while a southern population is distributed between Sambor and Mukdahan.

There also appears to be a small population in the Thakhek area. Those fish may belong to a stock in one of the larger tributaries in the area, from where the fish only occasionally venture out into the Mekong mainstream.

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