of the Fishery Board for Scotland. 



191 



side of the fish will quickly attain the same appearance as the sand or 

 mud on which it lives, and as the fish is also able to cover itself in the 

 sand and mud, I think the mortality amongst flat-fishes after this stage is 

 reached must be very small indeed. 



But then the above-mentioned great destruction must take place during 

 the development of the egg, in the larval and post-larval stages. The time 

 elapsing from the impregnation of the egg till the transformation takes 

 place varies with the different seasons and with different species ; but 

 there is reason to think that eight weeks will be the maximum time 

 for this more or less pelagic development. 



I may therefore be right in saying that perhaps 80 per cent, or 

 more of the five or six millions of eggs that a turbot may produce 

 in a season are destroyed within the first few weeks, and when this 

 is so, it seems reasonable that artificial protection during this difficult 

 period must be of the greatest importance. And it is just with these 

 views in mind that fish-culture has been adopted as a means of increas- 

 ing the supply of the valuable food-fishes. If such artificial protection is 

 possible, and can be realised in a practical way, it is, I think, clear that 

 the results of such work would be well worth the trouble, and this so 

 much the more as there is no other remedy known that may lead to the 

 same end without serious interference with the practical fishing industry. 



In the present hatcheries the eggs are protected during the whole of the 

 development, and the larval stage is also passed safely in the apparatus. 

 But as yet it has been necessary to plant the young larva? in the sea by 

 the time the yolk is absorbed, and the artificial protection has therefore 

 only been extended to the earliest part of this difficult period. When 

 planted in the sea, the larvae can, of course, be placed in the most favour- 

 able localities, and so far the young fish gets a good start. But the ad- 

 vantage of fish-culture would clearly be ever so much greater if the protec- 

 tion could be extended all through, till the time the flat-fish lives on the 

 bottom, with the habits of an adult. 



Once it was considered impossible to rear post-larval fish in captivity, 

 but this theory was untenable when Capt. Dannevig succeeded, in 1885, at 

 Flodevig, in rearing cod fry in a large tank. Dannevig's success was attri- 

 buted to the great capacity of the pond, and it was maintained that rear- 

 ing on a small scale was impossible. My above described experiment 

 with plaice in 1896 shows that this can also be done, and I feel sure that 

 continued experiments will soon show how similar work may be under- 

 taken on any scale with economy and facility. It is certainly much 

 easier to rear larval fish in a large enclosure than in a small one, because 

 the larger the enclosure is, the closer will the resemblance of its physical 

 circumstances be with those in the open sea. I shall only give an outline 

 of how I think such a rearing experiment with flat-fishes may successfully 

 be carried out on a large scale. There would be required a large enclo- 

 sure, the larger the better ; if failing to find a natural basin on the shore 

 that easily could be closed and modified, the most economical way, per- 

 haps, would be to dig out such a place in a sand bed near the sea, and line 

 it inside with concrete. Such a tank should not be deeper than from 8 to 

 12 feet, so the walls would not require to be strong. It should be on the 

 level with the sea and in communication with the latter with large drain 

 pipes with valves, so that the water supply may be taken directly from the 

 tide without pumping. Most of the forms of the marine fauna and flora, 

 which serve the post-larval fishes as food, can easily be produced in un- 

 limited quantities through cultures, and great numbers of fry could there- 

 fore find nourishment within a comparativaly small area. The success of 

 such an experiment would mean that such valuable fishes as the sole and 



