4.40 Fart III. — Twentieth Annual Report 



VII.— REPORT ON THH: OPERATIONS AT THE BAY OF 

 NIGG HATCHERY DURING THE SPRING SEASON OF 

 1901. By Haralb C. Dannevig. 



In several earlier reports on the work at the hatchery reference was 

 made to the desirability of being able to preserve the spawners from the 

 one year to the other. By so doing the difficulties attending the work 

 with newly confined fish would be avoided, while it was also anticipated 

 that a much greater number of eggs wovild be obtained. This anticipa- 

 tion had not been confirmed at Dunbar, owing in particular to the want 

 of a sufficiently large pond. The outcome of experiments pointed to a 

 negative result being due to such unsatisfactory conditions as would not 

 exist in a large pond, and no fears were entertained as regards ultimate 

 success in this respect. After the close of the spawning season at Bay 

 of Nigg in May 1900, the remaining large plaice were retained in the 

 y^ond, where they were regularly fed on shelled mussels, and already 

 during the latter part of the summer a development of the ovaries of 

 the females could be observed. This became more noticeable as the 

 season advanced. On October 26th twenty female plaice were examined, 

 and of these eleven were found to have been spawning during the 

 previous season and were again developing eggs normally ; seven more 

 were in a similar state, but were young fishes that apparently developed 

 eggs for the first time. The remaining two females had been egg-bound 

 dui'ing the previous season, and their ovaries were not visibly developed 

 at that date. The total number of plaice in the pond at this period was 

 625 of both sexes. During the third week of December another 397 

 were obtained from Aberdeen Bay ; these were young fishes, mostly 

 about the age of maturity. And at the end of the same month 184 

 larger plaice were brought from the Dornoch Firth. As will always 

 happen in consequence of injuries sustained during the capture, a portion 

 of these new fishes died soon after being put into the pond ; and on 

 January 8th, when all the plaice were examined, the total number was 

 1071. Of the females 560 were considered likely to spawn normally 

 during the following two or three months, while about 240 were 

 uncertain, and for the greater part immature fishes. 



The first sign of spawning was observed on January 1 2th, when a few 

 eggs were found in the water, The number was yet small, and continued 

 so for another week. On January 22nd the hatchery was started for 

 the season with 60,000 eggs which were collected from the surface- 

 water of the pond and placed in the hatching-apparatus for development. 

 This early commencement of the spawning corresponded very closely 

 with the ordinary period in the open sea, and since in previous years the 

 spawning at the hatchery was always much later, while at the same time 

 new fishes only had been used, the normal spawning on the present 

 occasion may safely be attributed to the presence in the pond of a con- 

 siderable number of old plaice that had already become thoroughly 

 acclimatised to confinement. Additional evidence in this respect must 

 also be recognised in the circumstance, that while in previous years the 

 spawning increased very i^apidly— with a rush as it were — the season 

 tliis year was more gi'adual. Disregarding the temporary variations 

 following upon extreme changes in the temperature of the pond-water, 

 it will be seen from Table I. that the spawning as a whole continued to 

 increase for about one and a half months, and the climax then reached 



