1902 Some spring Movements of Sea-Fish 99 



Some Spring Movements of Sea=Fish. 



By F. G. Aflalo, F.Z.S., F.R.G.S. 



That there is a general awakening of life around our coasts 

 at this season of the year is well known to all who live by 

 the sea, and both amateur anglers and professional fishermen 

 are once more plying their several operations. Some few of 

 our fishes, it is true, may be regarded as practically station- 

 ary within limited areas, but the fingers of one hand would 

 suffice to tally them, and they are without exception unim- 

 portant from the economic standpoint. The remainder are 

 a restless race, ever moving from place to place in the great 

 waters, but generally returning to favourite grounds — a feat 

 which, when we consider the density of the medium in which 

 they live and the comparative absence of characteristic land- 

 marks by the way, is almost more extraordinary even than 

 the homing of migratory birds. The migrations of fishes 

 are still very imperfectly understood, but at anyrate much of 

 the old belief in vast journeyings that comprised in their 

 scope the coldest seas of arctic latitudes has been dropped. 

 In its place we have a number of theories, most of which 

 bear the stamp of probability. 



Roughly speaking, these migrations of fishes are connected 

 with two primary instincts — feeding and breeding. The 

 fishes do not travel merely for recreation or for change of 

 scene, or so at least we may surmise. The element of 

 "change of air," so strong an inducement in our own migra- 

 tions, does not enter into their calculations, — if indeed they 

 do not move by instinct merely and not by calculation at all, 

 — for the density and chemical analysis of one part of the 

 Channel or North Sea are identical with those of another : 

 there is the same percentage, in all probability, of dissolved 

 or suspended compounds of arsenic, rubidium, magnesium, 

 manganese, sodium, gold, copper, and many other elements, 

 at Grimsby as there is at Penzance, or at anyrate the differ- 

 ence is so trifling that no fish could be aware of it. The 

 Baltic, it is true, has a very much lower percentage of solid 



