Taxonomy of Finfish

2.2.1 Meristics

Meristic characters which are countable have been widely used in studies of fish population and species. Unlike the body proportions or colouration, meristic characters are fixed usually at or before metamorphosis and remain constant throughout the life of an individual.

All the meristic characters should be treated separately and the frequency distribution of meristic characters must be given so as to find out any variation between species or between population of a species.

The following abbreviations are used in fins, scales and gill rakers of a teleost:

D – Dorsal fin

A – Anal fin

P 1 – Pectoral fin

P 2 or V 2 – Ventral fin

C – Caudal fin

L1 – Lateral line scales

Ltr – Lateral transverse row of scales

O – Adipose dorsal fin

Gr – Gill rakers

Dorsal fin count and anal fin count includes spines and rays. Among two dorsals one spinous and other ray type, then the formula may be given as D1 and DII where, DI stands for spinous first dorsal and DII stands for rays of second dorsal fin. If 3 spines and 7 branched rays are present in a single dorsal fin, then the formula may be given as DIII, 7.

The anal fin count includes spines and rays. If two spines and 5 rays are present, the formula may be given as AII, 5.

Pectoral fin count can be made on the left side. However, counts can be made on both sides in a few number of specimens to permit estimation of bilateral variations.

Pelvic fin count includes both spines and rays if present.

Fin count formula is given as below:

D1, I, VII-VIII - This denotes first dorsal fin with one spine separated from the

rest of spines (VII-VIII).

D2, I, 15-16 - This denotes second dorsal fin with one spine followed by

15-16 rays.

AII, I, 10-15 - This denotes anal fin with two spines separated from one spine

followed by 10-15 rays.

Fig added (Meristic Character) (FAO Figure)

Gill raker counts are for lateral gill rakers on the first arch, normally on the left side. The raker at the junction of the upper and lower limbs (epibranchial and ceratobranchial) is included in the lower limb count as the major part of the base of the raker is over the ceratobranchial. Rudimentary gill rakers, with the base width (lateral) of the raker equal to, or less than the raker length, occur at the anterior ends of the upper and lower limbs and these are included in the counts, though differentiated as ii, 7+19, iv=32.

Laterial line scales (L1) are scales along the lateral line from its origin to its posterior most part of the lateral line. In some teleostean fishes as in clupeids lateral line is absent. In such case scales will be counted along the row where the lateral line normally would have been present.

Predorsal scales are scales on the midline in front of the dorsal fin origin. These scales are counted as the scale rows which intersect the midline from the anterior point of the dorsal fin to the orbit.

Scales above and below the lateral line (Ltr) – A transverse series below of scale rows; below the lateral line scales are counted from the origin of the anal fin, not including the median ventral scale row, along a forward diagonal to the lateral line; above lateral line scales are counted from the origin of the dorsal fin, not including the median dorsal scale row, on a diagonal backward to the lateral line; the lateral line row is not included in these counts.