ICHTHYOLOGY. 



Clftssifica- both sexes are reduced to a state of remarkable emaciation. 



tion— Ma- The elongated nose, and hooked jaw, and brilliant colours, 



lacopteri. are almost immediately lost ; the old scales are cast, and 



"^— V-"^ the fish retire to some pool to regain their strength and 



com;)lete their new clothing. They finally redes'cend to 



the sea by easy stages, where their former condition and 



silvery lustre are regained, their strength invigorated, and 



all their functions so repaired as to enable tlieni ere long to 



renew their visit to the flowing streams, again to multiply 



their race. 



The ova continue covered by the gravel during the win- 

 ter, and begin to vivify fiom about the end of March to 

 the commencement of April. The fry remove from under 

 the gravel when nearly an inch in length, with the ovum 

 still attached ; and at this period, if the spawning bed or 

 furrow be turned up, it will appear in motion. We refer 

 to the article Fisheries for the details of Mr Shaw's 

 observation."', which prove that the young fish or Parr 

 may remain a full year in the fresh water. On the eve 

 of descending to the sea, the Parr assumes a more 

 brilliant dress and becomes a Smolt. At this time it 

 is from four to six inches in length, of a greenish gray 

 above, silvery below, the scales extremely delicate and 

 very deciduous. From the time the Smolts reach the sea, 

 for two months or ten weeks, we lose sight of them, and 

 can only inf(?r their growth from the tact, that after the 

 lapse of that period we find them again ascending the rivers 

 with a weight of from two and a half to four pounds. They 

 are then known under the name of Gilse or Grilse ; and 

 their size, as they ascend from the sea, increases with the 

 advance of the season. The Grilse which thus ascend 

 spawn during the ensuing winter, and are then entitled to 

 the name of Salmon. Descending in a weak state (as be- 

 fore mentioned), they retiu-n again in the summer of the 

 following year, as fish of from ten to fifteen jiounds weight, 

 according to special circumstances. A third year would 

 still increase their weight, as would several ensuing seasons, 

 till the attainment of an enormous size. Pennant, for ex- 

 ample, mentions a Salmon which weighed seventy-four 

 pounds ; and although we now regard with something of 

 wonder a fish which weighs even the half of that amount, 

 yet there is no doubt that not many years ago Salmon of 

 forty pounds were much more frequent than in these de- 

 generate days. The absence of Salmon of the largest class 

 from many of the Scottish rivers, where they formerly 

 abounded, is in fact owing to the injudicious perfection of 

 our fisheries, which occasions the constant capture of the 

 species in the state of Grilse, or other early condition ; and 

 the chances are by consequence greatly against any indi- 

 vidual escaping the various dangers by which it is en- 

 vironed, for such a succession of years as is likely to admit 

 of its attaining to its full dimensions. The destruction by 

 poachers, in the higher ])arts of the rivers, of the large en- 

 feebled Kelts, or fish which have completed their spawning 

 operations, is also extremely prejudicial ; for these indivi- 

 duals (almost utterly useless as food at the time alluded to) 

 would, if allowed to descend to the salubrious sea, ere long 

 revisit their native streams, greatly increased in size, and 

 full of health and vigour. A Salmon above fifty pounds 

 weight was taken, in 1835, at the mouth of the Leven in 

 Dumbartonshire. The general capture that season was 

 very great in Scotland. Nearly 800 were taken at one haul 

 in a bay of the island of Islay ; and our calculation, fi-om 

 accurate data, is, that for some time, about a hundred thou- 

 sand Salmon (including Grilse) were then shipped in Scot- 

 land weekh/ from our eastern ports alone. A friend of our 

 own lately saw a Salmon of sixty-one poimds weight on 

 a fishmonger's stall in London ; and as these sheets are 

 before us, we read in tlie Times of July 15, 1856, that 



239 



Salmon was caught at Chanonry Point, Moray Firth, 

 Fortrose, on the 10th, which weighed sixty-two pounds. 

 It was sent to London, and purchased by Mr Barton, fish- 

 monger, of Bishopgate Street. Similar causes have dimi- ' 

 nished the Salmon in the northern parts of the United 

 States of America. Hudson, in 1609, when sailing up the 

 river that bears his name, " saw great store of Salmons." 

 Now a solitary Salmon straying thither is a rarity. 



Dr Davy has for some years been in the habit of record- 

 ing his observations on the Salnioiiidce, and has made, with 

 his usual acenraey, a series of important experiments likely 

 to throw much light on the distribution of species. From 

 these, he concluded " that the ova of the Salmon, in an ad- 

 vanced stage, can be exposed to the open air, if dry, but a 

 short time, at ordinary temperatures, without loss of vitality ; 

 but for a considerable time, if the temperature be low and 

 if the air be moist ; the limit in the fiirmer case not having 

 exceeded an hour, whilst in the latter it has exceeded many 

 hours. The vitality of the ova was as well preserved in air 

 saturated with moisture, as it would have been had they 

 been kept in water. It was also preserved even when the 

 ova were included in ice, but if they were exposed to a 

 temperature many degrees below the freezing point, pro- 

 bably effecting their congelation, they were deprived of 

 their vitality. Both the ova and young fish were capable 

 of bearing a tenii)erature of about 80° or 82° in water for a 

 moderate time with impunity, but not without a loss of life 

 at a higher temperature than 84° or 85°. A degree of 

 saltness of water nearly equal to that of sea-water proved 

 speedily fatal to the ovum of the Salmon and to the young 

 fish ; the same effect was produced on the young fish by 

 brackish water of specific gravity 1016, but in a longer 

 time ; and when the solution is so diluted as to be re- 

 duced to the specific gravity of 1007, the advanced ovum 

 may be hatched in it, and the life of the young fish may be 

 sustained in it for many days but with diminishing power."' 

 From Dr Davy's excellent paper, the fact of temperature 

 having a still higher influence on the distribution of species 

 of fish than on the higher animals is apparent. An anadro- 

 mous fish must have its range restricted not only by the 

 temperature and suitableness in other respects of the afflu- 

 ents of a river in which it deposits its roe, but also by the 

 nearness to the equator of the mouth of that river. We 

 may, therefore, find Salmon in the streams flowing down 

 the northern side of a great watershed while they do not 

 exist on the southern side, though the feeders of both river 

 systems interlock at their sources. This Dr Hooker found 

 to be the case with the Tronts, which are confined to the 

 northern face of the Himalaya range. Dr M'Clelland has 

 described a species, ^'. orientalis, which inhabits the afflu- 

 ents of the Oxus. The parallel of 45° N. Lat. may be 

 roughly considered as the southern boundary of the common 

 Salmon in Europe, overlooking the feeders of the Atlantic 

 rivers which rise to the southward of that latitude ; and the 

 parallel of 41° may be taken as the limit in America, advert- 

 ing to the fact that the mean annual heat in a given parallel 

 of the latter continent in the temperate zone, is fi'om 8° to 

 15° of Fahrenheit lower than the parallel in Eui'ope. The 

 mean temperature of the year on these parallels lies between 

 45° and 52° Fahrenheit, and the mean heat of the hottest 

 month between 60° and 68° Fahrenheit. The heat of the 

 waters of the rivers frequented by the Salmon will, of course, 

 vary much less than that of the atmosphere, and fall far 

 short of the hottest months. 



Ausonius, in his poem on the Moselle, which we have 

 already had occasion to quote, says of the Salmon — 



" Nee te puniceo rutilantem viscere Salrao transierim," 

 a contrasting it with the characters of two other members of 



Classifica- 

 tion — Ma- 

 lacopteri. 



1 Phil. TVoMj., March 1856. 



