of the Fishery Board for Scotland. 



123 



II. — ON THE HATCHING OPERATIONS AT DUNBAR MARINE 

 HATCHERY during the Spring Season, 1895. By Harald Dannevig. 



In the Board's Twelfth Annual Report I gave a detailed account 

 of the operations at Dunbar Hatchery during the spring season, 1894. 

 From that paper it will be seen that plaice (Pleuronedes platessa) was 

 dealt with on a large scale, and that over 26,000,000 of fry were placed 

 in the waters of the Firth of Forth and St Andrews Bay. 



The physical conditions of the water in 1894 were, on the whole, very 

 favourable to the work ; the constant winds off-shore in the early part of 

 the season caused no heavy seas on the coast, which again resulted in 

 very clear and transparent water. Late in April and occasionally in 

 May the winds blew from the sea, but as they only continued a few 

 days at a time no great difficulty was encountered. The temperature of 

 the air as well as of the sea water was not in any way exceptional. 



During the season this year the general physical conditions were 

 somewhat different, the winds being nearly all the time off the sea, and 

 they continued to be very severe, so that in fact the herring fishing, which is 

 generally considerable in this locality during the winter months, was this 

 year nearly a failure, owing to the bad weather. The exceptionally low 

 temperature of the air in January and February also reduced the tempera- 

 ture of the sea water in the Forth very much. 



In Dr Fulton's account of Dunbar Hatchery last year, as well as in the 

 above-mentioned paper of mine, it is pointed out that an early collection 

 of the spawners was desirable, and would be a great benefit to the opera- 

 tions as a whole. In consequence of this it was the intention this year 

 to have as many spawners collected, as early as possible, as there is at 

 present room for at Dunbar. Several attempts were made in the winter, 

 but the continually stormy weather prevented this being begun before 

 the second week in February, as is described below. At the beginning 

 of the season a considerable number of unfertilised eggs were found in 

 the spawning pond and also in the creek, as is explained below. 



Before the work was begun, the filtering system was altered in order 

 to secure a better result with less expenditure of labour. The original 

 plan of nitration was to lead the inflowing water over horizontal frames, 

 covered with cheese-cloth or flannel of various degrees of fineness. 



But as the sea-water after storms sometimes contains a relatively large 

 quantity of sand or mud, blanket-cloth was found to be an excellent 

 material to purify the Avater thoroughly. The pores in these niters, 

 however, soon became closed, in which case the water remained on the 

 top of the frame, and subsequently passed over the edge of it without 

 any filtration at all. In this way, anything that was in the water found 

 its way into the hatching apparatus. 



Considerable attendance was therefore required to keep the filters in 

 order. To avoid the constant attendance, a new system of filtration has 

 this year been introduced, the principal idea being to force the water up 

 through fixed filters. This idea is due to Dr Fulton, and is referred to 

 in his account of the hatchery in last year's report. The original filter- 

 boxes were altered in the following way : — The supply pipe was carried 

 into the side of the box near the bottom. A few inches above this 

 level, fillets were fixed inside all around, indiarubber tubing being 

 attached on the top of it. 



On this tubing y the first frame (each of which is one inch thick) is 

 placed, being covered with galvanised iron netting of half ineh mesh, 

 which is fastened in a groove along the inner margin of the frame, and 

 therefore below the surface of the latter. The frame itself is made half 

 an inch smaller all around than the box inside, leaving an equal space 



