of the Fishery Board for Scotland. 



127 



spawning, are retained in the ovaries till they are destroyed. The facts 

 that have been stated above all strongly point to the importance of col- 

 lecting the spawners early — at least some months before the season begins. 

 But even then the same acclimatisation would be required yearly — early 

 or late ; injured fishes would be landed amongst the healthy ones, and 

 yearly cause the same harm and trouble. 



This would be avoided, or at least brought down to a minimum, if the 

 spawners were kept from one year to another. 



Such an arrangement is the only one by which the work can be carried 

 out on the largest scale and with the greatest security in regard to the 

 results. Twelve years' experience at the hatchery in Norway has led to 

 the same conclusion ; there it has always been found that spawners kept 

 in confinement for years are by far the best for breeding purposes. In 

 consequence of this, hundreds of fishes are there constantly retained, 

 although the severe winters cause difficulties that would not be met with 

 in Scotland. That fishes which have been kept in the same locality for 

 years form a better breeding-stock than those that have newly been 

 caught, is quite natural ; when constantly remaining in confinement, they 

 will first of all be accustomed to it, but the eggs are also developing 

 under the same circumstances in which they finally are spawned. 



4. On the Hatching Process. 



After the regular spawning began late in March, eggs were daily 

 collected from the pond and transferred to the hatchery. This process 

 was carried out in the same way as last year : — the eggs were separated 

 from any extraneous matter by the addition of fresh water, which causes 

 the eggs to sink to the bottom, so that the water can be poured off. The 

 accompanying table shows the daily progress of the operations. 



The total number of plaice eggs collected from the spawning pond and 

 transferred to the hatching apparatus was 44,085,000, and from these 

 38,085,000 fry were distributed in the w r aters of the Firth of Forth and 

 St Andrews Bay. The unfertilised eggs at first obtained from the pond 

 were separated as much as possible ; but a number were also mixed up 

 with the fertilised eggs when they were measured, and in this way in- 

 cluded in the total of eggs collected. This accounts for the higher 

 apparent deathrate in the boxes, — amounting to about fourteen per cent. 

 Last year, when practically no unfertilised eggs were collected the death- 

 rate was only 4*4 per cent. As will be seen from the table, the total 

 number in the hatching apparatus was sometimes considerable. From 

 April 21st to May 13th more than 20,000,000 eggs were undergoing 

 development, and during 13 days above 25,000,000. On such occasions 

 it was necessary to crowd the eggs in the boxes — sometimes to the extent 

 of about 400,000 per cubic foot of water; in such cases, of course, more 

 special attention is required, or the deathrate would be considerably in- 

 creased. On the 20th, 22nd, and 23rd of April about 6,000,000 eggs 

 were fertilised artificially. I have mentioned above that very clear water 

 delays the spawning to some extent ; this varies for different individuals, 

 and it has the greater effect on the fishes that are least vigorous from one 

 cause or another. About the middle of April the water was clearer than 

 usual, and I then found several fishes ripe, but apparently not spawning. 

 The eggs of these were for the most part artificially fertilised, and are 

 entered separately in the table, above the ordinary figure for collected 

 eggs, on the 20th, 22nd, and 23rd of April. 



The specific gravity of the water has this season been equally high and 

 constant, as it was last year — a matter of great benefit in hatching 

 operations on buoyant fish eggs. 



