METHODS FOR COUNTS & MESUREMENTSCounts of scales

Measurements

Scales are often difficult to be count without staining and/ormagnification. A practical method for temporary staining of bodydetails with cyanine blue is featured by Saruwatari et al. (1997).

All mesurements are taken in a straight line from point to point.

Lateral-line scales (yellow dots ● in right figure): number ofscales with lateral-line canals/pores, except for those on thecaudal fin. If the lateral line on the body is divided into twoparts (e.g., Oreochromis and some Ambassis), values of theanterior part (starting from the humeral areas) and posterior
part (ending around the caudal fin base) are represented
separately as "anterior part + posterior part" (e.g., 12+20).

Caudal-fin length (abbr. CL): length of the longest caudal-fin ray.

Predorsal scales (purple dots ● in right figure): number ofscales on predorsal midline.
Scales above lateral line (red dots ● in right figure) / scales
below lateral line (blue dots ● in right figure): number ofscales in a oblique scale row on body above or below lateralline; not including the lateral-line scale.

Body depth (abbr. BD): the greatest depth (vertical length)of body, unless otherwise noted. In some fish groups, it ismeasured at the pelvic-fin origin.
Caudal-peduncle depth (abbr. CPD): the least depth of the caudal
peduncle (measured vertically).
Caudal-peduncle length (abbr. CPL): length between theposteriormost point of the anal-fin base and the mid-lateral pointof the caudal-fin base (= structural base of middle caudal-fin ray,easily confirmed when the fin is bent laterally in many fishes).
Disc width (abbr. DW): the greatest width of disc [applied onlyto rays (stingrays) in the Mekong fishes].
Eye diameter (abbr. ED): the greatest diameter of the eye.
Head length (abbr. HL): length between the snout tip and theposterior-most point of the gill cover (including membrane).

Scutes (see figure on p.9): number of scutes along the ventral
midline of preanal area; these appear only in the clupeid
and engraulidid fishes amongst the Mekong fishes. Usuallyrepresented separately as "preventral (before pelvic-fin origin)+ postventral (behind) scutes" (e.g., 5+7)

Jaw length (abbr. JL): length between the mid-anteriormost
point and the posteriormost point of upper jaw or lip.

Circumpeduncular scales (green dots ● in right figure): allscales on a zig-zag vertical scale row encircling the narrowest
part of the caudal peduncle.

Length of dorsal-fin base (abbr. DB): length between theorigin (anteriormost point of base of first ray/spine) and the end(posteriormost point of base of last ray) of the dorsal-fin base.

Counts of fin rays and spines
Fin rays are usually counted separately into spines and rays(see characteristics of spine and ray on p.4). In the descriptive
accounts, spines and rays are designated by capital Romannumerals (I, II...) and Arabic numerals (1, 2...), respectively;
unbranched rays are sometimes designated by small Roman
numerals (i, ii...). Notation of the number of fin rays are asshown in the right figures, and the other Notes are noted below:
Dorsal- or anal-fin rays/spines (abbr. D): last dorsal- or analfin ray is split down to the base in many cases, appearing as
if it comprises two rays; if the last two rays appear to be incontact with each other at their bases, these rays are counted asa single ray (see right figures).
Caudal-fin rays (abbr. C): number of caudal-fin rays is usually
not so varied amongst the closely-related taxa; it is useful for
species identification of, e.g., Oryzias and Cynoglossus.
Pectoral-fin rays (abbr. P1): number and/or branching patternof pectoral-fin rays is sometimes useful for fish species identification. All rays are counted including minute and rudimental
ones.
Pelvic-fin rays/spines (abbr. P2): number of pelvic-fin rays/
spines is useful for many fish species identification. All rays/
spines are counted, even if their bases are in contact with eachother.

10

Length of anal-fin base (abbr. AB): length between the origin(anteriormost point of base of first ray/spine) and the end(posteriormost point of base of last ray) of the anal-fin base.

Pectoral-fin length (abbr. P1 L): length between the base of
first ray (= dorsalmost or anteriormost ray) and the distal tip ofthe longest ray of pectoral fin.
Pelvic-fin length (abbr. P2 L): length between the base of firstray/spine (= dorsalmost or anteriormost ray/spine) and thedistal tip of the longest ray of the pectoroal fin.
Preanal length (abbr. Prea. L.): length between the snout tip
and the origin (anteriormost point of base of first ray/spine) of
the anal fin.
Predorsal length (abbr. Pred. L): length between the snout tip
and the origin (anteriormost point of base of first ray/spine) of
the dorsal fin.
Prepelvic length (abbr. Prev. L): length between the snout tip
and the origin (anteriormost point of base of first ray/spine) of
the pelvic fin.
Snout length (abbr. SnL): length between the snout tip and theanteriormost point of the eye.
Standard length (abbr. SL): length between the snout tip andthe mid-lateral point of the caudal-fin base (= structual baseof the middle caudal-fin rays, easily confirmed when the fin isbent laterally in many fishes).
Total length (abbr. TL): length between the mid-anteriormost
point of the head (whether the lower jaw or the snout/upper jaw)
and the distal tip of the caudal fin; if the caudal fin is emerginate
or forked, dorsal and ventral lobes are squeezed together (towardsthe lateral midline) when the total length is measured.

● lateral-line scales (LLS)● scales above lateral line (TRa)● scales below lateral line (TRb)● predorsal scales (Pred. S)● circumpeduncular scales (CPS)12※In this specimen, formulae of scale counts
are represented as follows:
LLS: 28, Pred. S: 11, TRa: 7, CPS: 16

9 10 11
7 8653 4

ultimate scale for counting
lateral-line scales, locatedat end of caudal pedincle
12435

687

orcontinued toopposite side(total 16 in thisspecimen)

mid-ventral scale infront of pelvic-fin origin
iviiiii
i

1234
5
6

shoud be defined
which one is taken
IIIII

scale closest toanal-fin origin
IVVI
79VIIIVI VII※If dorsal fin is divided into two,values for 1st and 2nd dorsal finsare connected by a short hyphen

1～9I ～ VI

108

I

1～56
D: iv, 8 (or D br: 8)

D: VIII, 10● snout tip

examples of fin formulae(for each case)SL

anteriormost point ofsnout or upper lip / jaw(if projecting anteriorlybeyond snout)
Pred. LD: VI-I, 6※All lengths should be measured
from "point to point", except forDB
those of sharks and rays.
CLCPD

HL
SnL

JL
ED
P1 LDWCPLBD

ABP2 LPrea. LTL●mid-lateral pointof caudal-fin baseusually concealed under scales
and/or muscle / skin layer, buteasy to be located when thecaudal fin is bent (since caudalfin base appeared as shallow
vertical groove then)11