AN EXPLANATORY NOTE FOR USERS
Coverage. This book includes 568 fish species belonging
to 258 genera and 78 families, found in the Indochinese
Mekong. The term "Indochinese Mekong" is used to indicate
the Mekong Basin in Laos, Thailand, Cambodia and Vietnam;
namely, it does not cover the Burmese (Myanmar) Mekong andChinese Mekong. This book is actually not a comprehensive
guide for the fishes of the Mekong where ca. 1,100 species
are presumably found (Hortle, 2009), but almost all fishspecies commonly found in the Indochinese Mekong arethought to be covered at least. All fish species shown here
have been confirmed with repsective voucher specimensfrom the Indochinese Mekong during our field surveys in
2007–2013, unless otherwise noted. Some fishes, considered
to be the flagship species for the conservation purposes inthis region (e.g., highly threatened and/or extinct species),
are also shown here, even if we did not actually collect them[e.g., Balantiocheilos ambusticauda (Cyprinidae)]. The
brackish-water species and temporary visitors from coastal
marine waters, found in the tidal estuaries in the Vietnamese
Mekong, are also included. Although this book contains
several putative undescribed species, we do not give their newspecies descriptions here; these fishes will be described as newelsewhere, and some are now being studied by us.
Photographs and specimens. All photographs shown in thisbook were taken based on the specimens from the Indochinese
Mekong during the NEF Project in 2007–2013, unless otherwise noted. The photographed specimens were deposited in thefish collection rooms of respective institutions. The collection
abbreviations are as follows: CTU, Can Tho University, CầnThơ, Vietnam (preferred style of fish collection is CTU-P 123);
IFREDI, Inland Fisheries Research and Development Institute(IFReDI), Fisheries Administration (FiA), Phnom Penh,Cambodia (preferred style of fish collection is IFREDI-P 123);RLIKU, Research Laboratory of Ichthyology, Kasetsart University, Bangkok, Thailand; NUOL, Department of Biology,Faculty of Science, National University of Laos, Vientiane,Lao PDR (preferred style of fish collection is NUOL-P 123);
UNMF, Ubonratchathani University Natural History Museumof Fishery, Ubon Ratchathani, Thailand. Abbreviations of thephotographers are as follows: CG, Chaiwut Grudpan (UNMF,Thailand); HVM, Hieu Van Mai (CTU, Vietnam); JWRC,Japan Wildlife Research Center (Japan); KS, Koichi Shibukawa(formerly NEF, Japan); KU, Kenzo Utsugi (formerly NEF,Japan); LXT, Loi Xuan Tran (CTU, Vietnam); PM, PrachyaMusikasinthorn (RLIKU, Thailand); PT, Phanara Thach(IFReDI, Cambodia); TP, Thonglom Phommavong (NUOL,Laos); VP, Vannaphone Phutthana (NUOL, Laos); VV,Viengkhone Vannachak (NUOL, Laos). These abbreviations
are shown at the side of the respective photographs.
Text. Text was supervised by the editorial board (composedof delegates in respective involved institutions in the NEFproject), by adopting many discussions with participating
researchers in the NEF project, as well as several additionalfish research specialists whose names are listed in the acknowledgment section. Responsibility for correspondance in particular the scientific purposes is received by K. Shibukawa(Museum of Natural and Environmental History, Shizuoka,Japan), who wrote/compiled a draft manuscript of the text.

Classification and arrangement of fish taxa. Supragenerictaxa (e.g., orders and families) are arranged for the most partfollowing the systematic order of Nelson (2006). We havesometimes deviated from Nelson (2006) with respect to several
distantly-related fish families that look similar (e.g., Aplocheilidae and Adrianichthyidae). Even if they are not closely related,arranging similar-looking fish families close together can makethe identification of specimens easier for non-professionals.
Limits of the orders and families largely follow those of Nelson(2006), unless otherwise noted. Family code numbers, that are
being used for curatorial works of voucher specimens housedin participating institutions (see "Photographs and specimens",left), also follow those of Nelson (2006: 469–483); in thespecies accounts, the family codes are given after respective
family names (in parentheses, abbreviation: FC). Within afamily, genera/species are arranged based on similarities intheir general appearance; namely, similar fishes may be foundnearby within the family, but they do not necessarily have aclose phylogenetic relationship. This manner, however, maycause some difficulty for the search of the target species, inparticular with the large families with great species diversity(e.g., Cyprinidae), since the decision of "similar or different"
is merely the authors' subjective matter. The pictorial index ofspecies (pp. 26–31), arranging almost all fish species shownin this book as respective thumbnails of fishes, may help forsearching the target species.
Species names. All fish names are given with the scientificnames of respective species, as well as the authors and published years for respective names. Both vernacular and English
names are not included. In the Indochinese region, many offishes have more than a single vernacular names in each country
and, contrarily, many vernacular names may refer to some otherspecies in each (i.e., some or more fish species may be confused
under a single vernacular name); the "national standard"
common names of fishes is not yet developed, and there are nogood dictionaries of vernacular names of fishes in this region. In
order to provide the vernacular names, comprehensive grounded
researches are needed; the works are beyond a scope of thisbook.
Size and distribution data of fishes. Size of fishes is given
as its reliable maximum size, presented in standard length(SL), total length (TL), or disc width (DW, for stingrays only),with the respective references in parentheses. Methods for themeasurements are shown in p. 11. Size data is usually shown
to the nearest 0.1 cm (in species < 10 cm) or 1 cm (10 cm ormore). The other morphological data are primarily based on
the voucher specimens collected by ourselves, and complemented/reinforced by data of reliable references. Regarding
the distribution data, that in the Mekong Basin is given first,followed by whole (viz. worldwide) data of the respectivespecies. Data of fish distribution in the Indochinese Mekong
refers to the results of our field surveys in 2007–2013, as well
as reliable records in the literatures.
References. List of scientific articles cited and/or referred to inthis book is given in the last section.

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