52 SALMONID^ OF BRITAIN. 



B. xi— xii, D. 13-14 (t*:^), p. 13-14, V. 9, A. 11 (|:|), 0. 19, L. 1. 120-125, 

 L. tr. fi:|f, Vert. 59-60, Oaec. pyl. 53-77. 



The body is rather elongated, with the abdominal profile more curved than that 

 of the back. But the proportions of one part to the remainder in this fish vary 

 considerably, not merely consequent on the locality it inhabits, but likewise with 

 its age and the season : thus in the young there is a comparatively large head 

 and eyes, a short snout and rounded body : but as the adult stage is attained 

 there is greater depth of the body due to a more prominent abdomen.* After 

 breeding, the kelts are recognizable by low, lanky bodies and long heads. The 

 length of the head varies with the age and sex of the specimen, being 

 comparatively slightly longer in the par than in the female grilse or salmon, in 

 which latter, as age advances, the head becomes comparatively shorter, whereas 

 in the male it is longer than in the female. The length of the head is from 

 4^ to 4f or even 5 in the par and male salmon to 5 or 5j in the female salmon 

 and grilse, the caudal fin is from 6 in the par to 74 in the salmon of the entire 

 length : while the height of the body (which is greatest beneath the origin of the 

 dorsal fin) is from 4| to 5 in the total length. Bye — situated slightly in front 

 of the middle of the length of the head in the par (fig. 13), or nearly in the middle 

 of that length in breeding males (fig.- 14) and comparatively much smaller in 

 adult than in young fish : interorbital space convex and equal to about 2/3 the 

 length of the postorbital portion of the head in young, but more in old fish. 

 Snout much produced in the male, and during the breeding season the extremity 

 of the lower jaw is provided with a strongly curved prominence which in old 

 specimens precludes the closure of the jaws. The posterior extremity of the 

 maxilla reaches to beneath the middle of the eye in the par, but beyond its 

 posterior extremity in the adult : while it is comparatively wider in the young 

 than in the adult. Opercle higher than wide, from about 1/5 more in the par, or 

 1/4 in the grilse or young salmon, to 1/3 or even more in large salmon, (Plate 1) : 

 subopercle from 1/2 to 1/3 of the height of the opercle, while its posterior margin 

 forms a semi-circular curve along with that of the opercle. Preopercle with its 

 angle rounded and having a rather distinct lower limb. Tarrell observed that 

 what distinguishes Salmo solar from all other British species is the form of the 

 opercular bones, which have a rounded outline to the posterior edge of the 

 gill-covers, the longest diameter of which to the nose would be in a line through 

 the eye, while in all other British migratory species the same line would pass 

 below the eye. And this definition, although not absolutely correct in all 

 instances, will be found to be so in the great majority, as shown in the lines 

 A to B in figures 13 and 14 of the par and old male salmon. 



Fig. 13, Head of par, natural Fig. 14. Head of old male salmon, 



size. two-elevenths the natural size. 



* Professor Benecke (German Fisheries Association, March 4th, 1886) adduced some 

 interesting figures regarding the weight and corresponding length of some German salmon 

 wherein he showed that one measuring 45-7 inches in extent, can in the same water weigh from 

 16 lb. to 30 lb. which would occasion considerable difference in the various proportions of the bodv 

 to that of the entire fish, *^ •' 



