PROPAGATION OF FISH. 



Information of the highest importance on the artificial propagation of fish was laid 

 before the late meeting of the British Association. Experiments with salmon, made 

 at Perth, Scotland, have been extremely successful. Three hundred boxes were laid 

 down in twenty-five parallel rows, each box partly filled with clean gravel and peb- 

 bles. On the 23d of December, 1853, 300,000 ova were deposited in the boxes. 

 On the 31st of March, 1854, the first ovum was observed to be hatched, and in 

 April and May the greater portion had come to life, and were at large in the boxes ; 

 in June they were admitted into the pond, their average size being about an inch 

 and a half in length. From their admission to the pond the fry were fed daily with 

 boiled liver, rubbed small by the hand. By spring of the present year they had in- 

 creased in size to the average of three and four inches in length. On the 2d of 

 May a meeting of the Committee was held at the pond, to consider the expediency 

 of detaining the fry for another year or allowing them to depart, but it was thought 

 they had not assumed the migratory dress till the 19th, when the sluice communi- 

 cating with the river Tay was opened, and every facility for egress afforded. Con- 

 traiy to expectation, none of the fry manifested any inclination to leave the pond 

 until the 24th of May, when the larger and more mature of the smelts, after having 

 held themselves detached from the others for several days, went off in a body. A 

 series of similar emigrations took place until full half the fry had left the pond, and 

 descended the sluice to the Tay. It has long been a subject of controversy whether 

 the fry of the salmon assume the migratory dress in the second or third year of their 

 existence. So favorable an opportunity of deciding the question as that afibrded by 

 this experiment, was not to be overlooked. 



In order to test the matter in the fairest possible way, it was resolved to mark a 

 portion of the smelts in such a manner that they might easily be detected when re- 

 turning as grilse. A temporary tank, into which the fish must necessarily descend, 

 was constructed at the junction of the sluice with the Tay; and as the shoals suc- 

 cessively left the pond, about one in every hundred was marked by the abscission of 

 the second dorsal fin. A greater number were marked on the 29th of May than on 

 any other day, in all about 1200 or 1300. The result has pi'ovcd highly satisfactory 

 and curious. Within two mouths of their liberation, twenty-two of the young fish 

 so marked when in the state of smelts on their way to the sea, have been, on their 

 returning migration up the river, recaptured and carefully examined ; the conclu- 

 sions arrived at are most gratifying, and proved what has heretofore appeared almost 

 incredible, the rapid growth of the young fish during their short sojourn in the salt 

 water. Those taken first weighed 5 to 5 J lb, then increasing progressively to 7 and 

 8 lb, whilst the one captured on the 31st of July weighed no less than 9 J lb. In 

 all these fish the wound caused by marking was covered with a skin, and in some a 

 coating of scales had formed over the part. 



