274 



HAEDWICKE'S SCIENCE-GOSSJF. 



hence it is that we know how the fry have fared 

 during the past nine or ten months — the period 

 representing their age. A visit to an estabhshment 

 like that of the Midland Counties Fish-Culture 

 Establishment, at Malvern Wells, Worcestershire, 

 is the means of affording more practical information 

 in the space of an hour than we could possibly 

 gather, by dint of much exertion, in open waters 

 during a period occupying, perhaps, several months. 

 Indeed, it is impossible to ascertain the truth of 

 certain ichthyological matters unless investigations be 

 carried on under semi-artificial circumstances, whereby 

 the objects of study are always accessible. 



When I last visited the Establishment referred to, 

 in the early part of last summer, the young trout 

 and salmon fry, hatched out during January and 

 February of the present year, were about two inches 

 in length, now they measure six inches. But it must 

 not be thought that all the young fish have achieved 

 similar dimensions to that mentioned. Like all other 

 animals, fish vary greatly in size, and while one 

 yearling trout may be seven inches long there are 

 not a few that attain to only two inches at that period 

 of their existence. It is possible that the difference 

 in the rate of growth is more marked among fish than 

 other animals. However this may be, we cannot 

 but recognise in this diversity the fact that it forms 

 part of the system which Nature provides against 

 over-population of waters. As it is, the smaller fish 

 are preyed upon by the larger ; and the fish-culturist 

 knows only too well that unless he steps in at the 

 juncture of affairs, when the fish reared by him are 

 old enough to obey their instincts and fall upon the 

 smaller and weaker of their congeners, he will lose a 

 large proportion of them and thus become defeated 

 in his endeavours to outdo Nature. He, therefore, 

 adopts the course of isolating the larger fish, first 

 sorting them into sizes, and the dire effects of canni- 

 balism are thereby frustrated. 



The process of sorting the fish was recently carried 

 out before me and others, by Mr. Burgess, the 

 owner of the Establishment mentioned, and afforded 

 me great interest. All the " nursery " ponds, in which 

 the young fish have been reared during the spring 

 and summer, were subjected to a thorough examina- 

 tion and minute inspection. The plan adopted was 

 to draw the water off from each pond, leaving only 

 sufficient for the fish to inhabit during the investiga- 

 tion. And here, let me say, that each pond is so 

 constructed as to be quite independent of the other, 

 so that the water can be drawn off from any one 

 habitat without interfering with those adjoining it, 

 and without occasioning a cessation of the water- 

 supply. While the water is running away from the 

 pond, and its volume grows less and less, it is 

 interesting to note the behaviour of the fish, which 

 exhibit a certain amount of excitement and much 

 activity, as the water leaves them. Their efforts to 

 go with the stream, which gushes forth from the 



waste-pipes, are frantic but ineffectual, as are also 

 their subsequent endeavours to hide from view and 

 enshroud themselves in holes and corners in their 

 dread of being launched into our element, which is 

 equally fatal to them as theirs is to us. But Mr. 

 Burgess's arrangements are so made that the fish are 

 never totally deprived of water, and while the opera- 

 tion of sorting them is in progress, they are well 

 provided for and their physical condition carefully 

 watched, so that not a single death ever occurs. As 

 the fish are presented to view when the water partially 

 flows away, we are enabled to inspect them closely, 

 and as we do so, we marvel that in so short a space 

 of time they have grown so rapidly. But on examin- 

 ing the water closely we note the cause of it, inas- 

 much as it is alive with all kinds of animate food 

 upon which the fish have built themselves up. The 

 operation of sorting over, and the smaller fish having 

 been removed from destruction, the water is re-ad- 

 mitted, to the great satisfaction of the fish remaining 

 in the pond. The other ponds are similarly treated 

 till they have all been overhauled, and their occupants 

 weeded out and accommodated with habitats cor- 

 responding with their size. It is doubtless more 

 convenient to maintain them according to age, but 

 it will be seen that, owing to the wide diversity of 

 growth, such a course is incompatible with the prin- 

 ciples of fish-culture. It is believed by the uniniti- 

 ated that all fry are of corresponding size when they 

 emerge from the ova. This is a great error. To 

 begin with, the eggs are of different sizes, and it will 

 be seen on examining the alevins that there is a 

 remarkable difference also in their dimensions. 

 Without doubt food and other conditions of habitat 

 tend to influence their growth, and therefore it does 

 not follow that because an alevin commences its 

 career at a size below the ordinary standard, it 

 remains a dwarf, any more than a full-sized one will 

 develop into a big fish if the conditions necessary to 

 its prosperity are absent. Again, fry may become 

 weak, and therefore less able to seek and obtain food, 

 and in this way be prevented from thriving ; or they 

 may suffer from a paucity of food at the outset of 

 their careers, just when they have absorbed their 

 self-contained sac, and in consequence of this never 

 recover. 



Judging by the results produced at fish-cultural es- 

 tablishments, the past spring and summer have been 

 very favourable to fish-rearing ; and the satisfactory 

 reports made by fish-breeders as to the health, fine 

 growths and absence of disease among their Sal- 

 monidx confirm this opinion. 



Ichthyologist. 



The Christmas Lectures to juveniles will this year 

 be on "Life in Motion, or the Animal Machine" 

 (experimentally illustrated), and will be delivered by 

 Professor John G. McKendrick, M.D., F.R.S., the 

 professor of physiology in the University of Glasgow. 



