TENCH. 
749 
The average length of the Tench in Sweden is 
about 2 or 3 dm. The largest specimen Ekstrom ever 
saw was 47 cm. long — already an extraordinary size 
— but Nilsson had a specimen nearly 55 cm. in length. 
According to Blanchard the fish attains at the age 
of one year a weight of about 125 gm., at the age 
of three years about 1 — 1 1 / 2 kgm., at the age of six 
or seven years 3 — 4 kgm. This last weight is gener- 
ally given, on Bloch’s authority, as the maximum 
weight of the Tench, and according to the reports sent 
in to the Swedish Fisheries Committee of 1881 the 
species attains in the District of Jonkoping a weight 
of 8 Swedish pounds (3% kgm.), but this statement 
needs confirmation". According to Fatio Tench 4 dm. 
long weigh about 1 7 3 kgm., and Tench 5 dm. long 
27a kgm- 
The body is thick, but laterally compressed and 
fairly deep, the greatest depth, at the beginning of the 
dorsal tin, being more than 7 4 of the length 6 . The 
depth is comparatively greatest, however, in the hind 
part of the body, for the Tench is the only one of our 
Cyprinoids in which the minimum depth of the tail, at 
least in adult specimens, is about 14 % c (13 1 / 2 — 15 1 / 2 %) 
of the length of the body or 3 /s (58 — 65 %) of the length 
of the head**. The dorsal profile ascends only slightly, 
but in a regular curve. The back is convex through- 
out its whole length, flatter behind than in front of 
the dorsal fin. The belly, on the other hand, is flatter 
in front of than behind the ventral fins, but in the 
males is sometimes concave in the median line between 
the ventral fins and the anal fin. 
The head, the length of which is about 22 — 24 % 
of that of the body, is thick and somewhat compressed. 
Its breadth is about equal to its vertical depth at the 
anterior margin of the orbit. The forehead is broad 
and evenly convex, and lies in a line with the snout 
and occiput. Its breadth is always somewhat (about 
7, 0 ) greater than the length of the blunt snout, which 
in adult specimens occupies about 38 % of the length 
of the head. The mouth is small, but turned sharply 
upward; the lips are thick. The length of the barbel 
at the corner of the mouth is usually less than half 
the diameter of the eyes. The length of the upper 
jaw is about 1 / i (24 — 27 %) and that of the lower jaw 
about 7s (30 — 34 %) of the length of the head. The 
lower jaw is always somewhat shorter than the suture 
between the suboperculum and the operculum, which 
suture is as a rule equal in length to the snout. The 
eyes are small, but comparatively larger as usual in 
young specimens: during the growth of the fish from 
15 to 40 cm. their longitudinal diameter (slightly greater 
than the vertical) varies between about 15 and 13 % 
of the length of the head or 40 and 34 % of that of 
the snout. They are set about half-way between the 
occiput and the tip of the snout, and so high that the 
line from the middle of the margin of the upper jaw 
to the middle of the caudal fin touches the inferior 
margin of the iris. The nasal cavities, which lie twice 
as far from the tip of the snout as from the eyes, are 
furnished, here as in the preceding genera, each with 
two closely adjoining nostrils. The anterior nostril is 
the smaller and has a projecting dermal flap at the 
hind margin. The gill-openings are fairly large, their 
height being about equal to the least depth of the tail. 
The opercula are smooth, rounded at the margin, and 
furnished with a broad rim, which extends from the 
upper angle of the gill -opening to the point where the 
branchiostegal membrane is attached to the isthmus, at 
a, distance of half the diameter of the orbits from the 
branchiostegal membrane of the other side. The three 
rays in each branchiostegal membrane are bent, broad, 
and strong. The gill-rakers are short and scattered, 
numbering about 13 in the outer row on the first 
branchial arch, 16 on the outer margin of the pha- 
ryngeals. The five, or sometimes only four (more usu- 
ally five on one side, four on the other) pharyngeal 
teeth (fig. 187) are more or less (the foremost tooth 
least) transversely (behind and in front) compressed, 
with simple masticatory surfaces, depressed in the trans- 
verse median line, and with the upper inner corner 
more or less (most in the hindmost tooth) hooked. The 
pharyngeal cartilage is reddish brown like horn, of a. 
pointed oval shape (triangular with rounded lateral 
corners and arcuate anterior margin), and almost hooked 
a Yarrell tells us (from Daniel’s Rural Sports') of a Tench 33 in. long and 11 lbs. 9 4 oz. in weight, which had long lived 
closely confined among some roots in a pond choked up with mud. 
b In adult specimens about 27 — 31 % of the length of the body. In young specimens about 7 cm. long this percentage is about 
21, according to Canestrini. 
c In young specimens, however, according to KR0YER, about 11 */ 2 %. 
d In exceptional cases, however, these percentages may be found in the Crucian Carp and the White Bream. 
