This document provides information on the external morphology of common cultivated carps in Nepal. It describes the key features of the Rohu fish in detail, including its body regions of head, trunk, and tail, mouth and eye placement, fins, scales, and coloring. It also briefly outlines distinguishing characteristics of other common carps found in Nepal, such as the Common Carp, Grass Carp, Bighead Carp, and Mrigal. The purpose is to teach students to identify different types of cultivated carp based on their external morphological characteristics.

1. EXTERNAL MORPHOLOGY OF A FISH

2. OBJECTIVE:
It is important to study the essential features
of fishes for their body structures and
functions on the basis of their morphological
characteristics. This exercise helps the
students to distinguish the different kinds of
fishes among cultivated carps of Nepal.

3. INTRODUCTION:
Fishes are the first successful class of
chordates. They are aquatic cold blooded, gill
breathing vertebrates which propel and
balance themselves by means of fins.
In the different types of water systems of the
world there exist a large number of fish
species differing widely in shape, size, habits
and habitats.

4. Inspite of many variations, body of fishes is
generally fusiform and steamlined. However,
in puffers the body is globe shape and in eels
is of serpentine form. The ground plan of body
is bilateral symmetrical with prominent lateral
line system. Appendages of fishes comprise
the fins and cirrhi (flaps of flesh). Paired fins
are pectorals and pelvics (Ventrals) while
dorsal, anal and caudal fins are unpaired fin.

5. In some forms there are two dorsal fins, the
first being spiny and second being soft,
supported by fin rays. Cultivated carps of
Nepal include both indigenous and exotic
fishes. These are Rohu (Labeo rohita), Bhakur
(Catla catla), Mrigal (Cirrhinus mrigala),
Common carp (Cyprinus carpio), Silver carp
(Hypophmthaalmichthys molitrix), Bighead
carp (Aristichthys nobilis) and Grass carp
(Ctenopharyngodon idella).

6. EXTERNAL FEATURES OF TYPICAL FISH
Rohu (Labeo rohita):
Rohu is a cultivated indigenous carp.
Fig 2. Rohu (Labeo rohita)

7. Of all the cultivated carps, the Rohu is
considered as the most tastiest fish in this
subcontinent and is common in the rivers and
streams of Terai parts of Nepal. It varies
greatly in size according to its environment. In
large rivers it may grow to nearly a meter in
length.

8. Body regions:
Entire body of a fish may be divided into heads,
trunk and tail. The region from the snout to the
posterior edge of the operculum is the head. The
trunk extends from the operculum to the anus.
The post anal region is the tail.
The body is moderately elongated, rounded,
thickest in the middle and tapering to the tail.
The mouth is situated anteriorly, opening
ventrally in the head in terminal position with
thick fringed lower lip. A pair of small maxillary
barbells present.

9. The large eyes are situated on lateral side of
the head is the operculum or gill cover, a large
flap which when raised, displays the gills.
On the ventral surface of the body at about
two thirds distance from the snout to the end
of the tail is the anus.

10. Fins:
There is a single dorsal fin supported by 16 branched rays.
The caudal fin is deeply forked and supported by 19 fin
rays. There is single large anal fin supported by 7 rays. The
pectoral fin has 17 rays and is situated in the normal
position. Close behind the gill opening, but the pelvic
(ventral) fin shifted its position and lies some distance
infront of the vent. It is supported by 9 rays. Both pectorals
and the pelvic fins are paired fin. The dorsal, caudal and
anal fins are also called the median fins.
Body covering and colouration:
The body is covered by a soft slimy skin along with the
scales of moderate size. On the head and fins skin is
smooth and devoid of scales. Body color bluish black along
dorsal side becoming silvery with reddish tinge on sides.
Fins are black.

11. Identifiable Peculiar characteristics of different cultivated
fish species in IAAS, Sundarbazar, Lamjung as follows;
ii. Common carp (Cyprinus carpio):
Common carp is characterized by a flat and deep body,
short and small head, protactile mouth and two pairs of
maxillary barbells. The dorsal fin is long with a sharp
spine.
iii. Grass carp (Ctemopharyngodon idella):The body of fish
is elongated and cylindrical with large greenish scales.
Head broad, barbells absent and mouth subterminal
with upper jaw slightly longer than the lower jaw.

12. Usually it has toothless mouth, but has a
specialized pharyngeal teeth for grasping aquatic
vegetation. Gil rackers are short and sparse.
Bighead carp (Aristichthys nobilis):
The body of fish is flat, laterally compressed and
covered by small silvery scales brownish above.
Head long and massive, barbells absent, mouth
large, upturned with lower jaw longer than upper
and the abdominal keel is incomplete. The
posterior margin of the pectoral fin extends
beyond the base of the pelvic fin.

13. Mrigal (Cirrhinus mrigala):
This fish is characterized by elongated and
cylindrical body, small head and sub-terminal
mouth with thin non-fringed lips. One pairs of
small barbells are present. The upper jaw is
longer than the lower jaw. The body color is
grayish on dorsal side and whitish on belly, but
is not pinkish as rohu.

14. Lateral line:
A well marked lateral line extends along each side from head to tail.
And is continued into branching lines on the head. The lateral line is
a small line of nerve cells and is an area of sensitivity that helps the
fish feel pressure and temperature changes in the water around it.
Materials Required:
Freshly killed or formalin preserved fish.
Tray
Forceps
Needles
Gloves
Procedure:
Take a freshly killed or formalin preserved fish and identify its major
body parts. Count the fin rays and lateral line scales.