by a series of pores. The lateral line is usually distinguished by modified and, often,
f. Barbels. Barbels are fringes of skin (tentacles) that are normally located on
the snout or lower jaw. Barbels are used to feel and possibly to smell food. An
example of a fish with barbels is the Pacific Ocean perch.
g. Gill Covers. The gill cover is a protector for the gill openings (sometimes
called operculum). It is located close to the nape area.
h. Nape. Generally, this is where the head is separated from the rest of the
i. Caudal Peduncle. This is the fleshy portion of the fish that extends from the
posterior end of the anal fin to the end of the tail. It does not include the tail fin. The
small amount of connective tissue found in fish flesh is more pronounced in this area,
making steaks and fillets from this area less desirable.
EXTERNAL IDENTIFICATION - FINS
a. General. Fins are classified by their location (see anatomical terms above).
Their functions are locomotion, balance, and protection. The type, number, location,
and structure of fins are decisive in species identification. Fins are either medial
(middle) or paired. See Figure 1-1.
b. Medial Fins.
(1) Dorsal fin. Some species have one dorsal fin along the back, some two,
while others may have three. The dorsal fin (located on the dorsal border) aids in
stability while swimming. In some species, the dorsal fins contain hard needlelike
bones (called rods) that may be used as a means of protection.
(2) Adipose fin. This is a fleshy appendage that has no specific function, yet
is found on some species, for example, salmon.
(3) Caudal fin. The caudal fin (tail fin) is the main fin of movement and is
located on the posterior end of the body. By flexing the muscles on one side of its body,
the fish moves its caudal fin in that direction, Then, it moves the caudal fin in the
opposite direction by flexing the muscle of the alternate side. Alternate flexing causes
the fish to move forward, thus the term "fish tailing."
(4) Anal fin. Some species have one anal fin, some two. It assists in
stabilization. It is located just posterior to the anus or vent.