of the Fishery Board for Scotland. 75 



APPENDIX IV. 



NATURAL HISTORY NOTES. 



By W. L. CALDERWOOD. 



(a) Smolts Reared in Salt Water, 



In September 1 901, a sea pond, which had been excavated in the beach at 

 Tugnet, at the mouth of the river Spey, was completed, and a syphon pipe 

 adjusted for the tidal supply of salt water. This pond was constructed 

 in connection with the salmon hatching operations which for some years 

 have been carried on at Fochabers under instruction of His Grace the 

 Duke of Richmond and Gordon, and as an elaboration of the rearing of 

 the fry in the ponds at Cunninghaugh, near the mouth of the Spey. Mr, 

 Muirhead, the Duke's commissioner, and Mr. Rae, the manager of the 

 extensive salmon fisheries of the estate, have from time to time very 

 kindly supplied me with information respecting the rearing operations, 

 and I have repeatedly visited the ponds. 



In 1901 many of the smolts which had been reared to their natural 

 period of seaward migration, i.e., about 26 months, were retained in the 

 fresh-water ponds pending the completion of the sea pond above referred 

 to. In May they had been active silvery little fish, but by September, when 

 the pond was ready, they had reverted to the more sombre parr colour- 

 ation. Twenty-five of these two-year-olds were introduced in the middle 

 of September into pure sea water in the new pond. They ceased feeding 

 at once, and in a few days four were dead. The salinity of the pond 

 was then reduced by about half, through the introduction of fresh water. 

 The fish at once recommenced feeding, and it was at the same time 

 noticed that a clear silvery dress was again assumed. The food supplied 

 was the chopped liver used at the fresh-water ponds. 



These few young fish having been successf uly established in sea water, 

 the pond was stocked with 500 salmon smolts. 



In May 1902, while some repairs were being made to the super- 

 structure of the pond by a carpenter, it was noticed that the fish had 

 become frightened, and presently that they were turning up, sick, in 

 large numbers. The water in the pond at the time was four feet in 

 depth. Mr. Rae was hastily summoned, but, in spite of efforts to aerate 

 the water, some 400 of the fish died. The remaining hundred were 

 removed from the pond and carried back to the fresh-water ponds of 

 Cunninghaugh. It was subsequently discovered that a considerable 

 quantity of disintegrated seaweed had been carried into the Tugnet 

 pond by the syphon through the beach, and it was believed that the 

 rapid movements of the frightened fish stirred up this sediment to such 

 an extent that the water became poisoned by the gasses from the 

 decomposing seaweed. Twelve of the dead fish were sent to me for 

 examination, and I afterwards received also a sample of the sediment, 

 which was analysed. The fish were distinctly silvery in appearance, 



