OF THE SEA-TROUT OF THE SOL WAY. 373 



at the usual season of migration. In support of such views, we have the autho- 

 rity of Dr M'CuLLOcn, who states, that sea-trout are now permanent inhabitants 

 of a fresh- water loch in the island of Lismore. 



Having detailed the several particulars relating to my experiments on the 

 ova of the sea-trout up to the migratory stage of the brood, it will now be ne- 

 cessary to recur to the results of experiments made on the fry while migrating to 

 the sea. 



On the 9th of May 1836, having observed the salmon fry descending towards 

 the sea, I took the opportunity of capturing a number of them, by admitting them 

 into the salmon cruive, and, on examination, I found about one-fifth of each 

 shoal to be what I regarded as sea-trout ; and conceiving this to be a favourable 

 opportunity of ascertaining the fact by actual experiment, I proceeded to mark 

 every individual of that species which entered the cruive in the course of the day. 

 They amounted to about 90. A fresh, however, taking place in the river in the 

 evening, prevented my following out the experiment any farther that season. In 

 experimenting on migratory fishes at 25 miles distance from the sea, windings in- 

 cluded, the chances of recapturing the individuals marked is comparatively small, 

 and I therefore did not calculate upon retaking more than an individual or two 

 out of the 90. My expectations were not agreeably disappointed by any better 

 success than I had anticipated. However, on the 1 6th July, just 80 days after- 

 wards, I recaptured a herling in the cruive, with the mai'k which I had put upon 

 the young sea-trout of the previous May, viz., the whole of the adipose fin being 

 taken off, and three-fourths of the posterior rays of the dorsal fin removed. It 

 measured about 12 inches in length, and weighed 10 ounces. The average weight 

 of the sea-trout fry, at the age at which they migrate to the sea, is about 

 3^ ounces, so that the specimen referred to exhibited an increase of weight of 

 6|r ounces in about 80 days' residence in salt water. It was my intention to have 

 retained specimens of the several individuals on their return from the sea, as they 

 were successively retaken, with the view of exhibiting more correctly the deve- 

 lopment and growth of the species in salt water. This single specimen, however, 

 of that year having been injured in the cruive, was deemed unfit for the object in 

 view, and was therefore set at liberty, in the hope of obtaining one in a more per- 

 fect state. In this, however, I was disappointed, no other having presented itself 

 during the remainder of that season. But No. 9 is a specimen of the herling of 

 the Nith, taken from the river in July, and is exhibited as an example of the next 

 progressive stage ensuing that of the silvery condition of the smolt or fry (No. 8). 

 It may also be considered as a correct representative both of the specimen alluded 

 to, and of the general state of the species at that age. These herlings enter our 

 rivers in most abundance in the months of July and August. 



No. 10 is a specimen exhibiting the next state of advance beyond the her- 



VOL. XV. PART III. 5 H 



