of the Fishery Board for Scotland. 



177 



have vessels stationed at Shetland to watch for the advent of the northern 

 shoals, and to give notice down the east and west coasts to enable the 

 fishermen to fish in the proper places. 



The views now current assume that fish do not as a rule travel far, and 

 competent fishery authorities believe that even Firth herrings (e.g., Loch- 

 fyne, Firth of Forth) do not leave the Firths, but merely disperse into 

 deeper water. Similarly, it is generally held that flat-fish do not wander 

 to any considerable distance. I believe the tendency of opinion is to go 

 too far in this direction • but the question can only be settled by experi- 

 ments and careful observations. 



The experiments, the results of which are detailed in the following 

 pages, were begun four years ago. In beginning the experiments pre- 

 liminary difficulties had to be considered, namely, how the fish could 

 be marked in such a way as to make the marking permanent, conspicuous 

 enough to be easy of recognition to those who caught the fish, without 

 rendering the latter too conspicuous to its enemies, and capable of indi- 

 cating the necessary particulars of the experiments, such as where and 

 when the fish was marked, its size, &c. It was also desirable that the 

 method should injure the fish as little as possible, and be inexpensive, 

 since large numbers had to be dealt with. Many expedients were tried. 

 Pigment was used, but the fish died ; and this method was otherwise un- 

 satisfactory. It was decided that the method most likely to succeed was 

 to attach a label or tag, bearing a number, to some part of the fish. In 

 order to ascertain what suitable substance might best resist the action of 

 the sea, pieces of leather, gutta-percha, india-rubber, lead, copper, zinc, 

 brass, &c, were immersed for several weeks in sea-water, and brass was 

 ultimately selected as the substance which was, on the whole, most satis- 

 factory. It was also decided that the tag should be fastened round the 

 tail of the fish. A thousand thin brass circular discs, three-quarters of an inch 

 in diameter, were procured, each having a consecutive number stamped on 

 it, and pierced with a small hole at opposite sides by which it could be 

 fastened to the fish. At first, thin aluminium wire was used for this 

 purpose, from the fact that sea-water does not corrode it, and over 500 

 fishes had the discs thus attached to them, but not one of these was re- 

 captured ; and check experiments on fish in the tanks showed that the 

 aluminium becomes brittle and breaks. Black silk cord was eventually 

 employed, and has proved quite satisfactory, resisting the action of the 

 sea-water for at least more than two years. The disc was also found to 

 be rather large, especially for small fish, and the one now employed is 

 oval and smaller. 



While the method described has been found satisfactory in tracing 

 the migration of the fish, it has a disadvantage from another point 

 of view. As was anticipated, these experiments throw considerable light 

 on the important question of the rate of growth of fishes; but 

 owing to the fact that the ligature around the tail causes abrasion in 

 nearly all cases, the natural growth is retarded. This is referred to more 

 fully later on. In order if possible to obviate this disadvantage, experi- 

 ments were made by attaching very small oblong discs of aluminium and 

 silver to the outer surface of the opercular covering of fish living in the 

 tanks (without penetrating to the inner surface), but in the course of a 

 few months they all came off, and even this comparatively slight interfer- 

 ence was found to check the growth of the fish, which were measured 

 and weighed periodically. Some of them, indeed, fell off in weight, and 

 took little food. Recently another method has been tried by securely- 

 fixing a small oblong brass tag, just large enough to contain the number, 

 to the shank of a small fish-hook, and imbedding the hook in the 

 thick fleshy part of the back. Sufficient time has not elapsed to show 



