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Part III. — Eighteenth Annual Report 



VIII. — REPORT ON THE OPERATIONS AT DUNBAR 

 MARINE HATCHERY DURING THE SPRING SEASON 

 1899. 



By Harold C. Dannevig. 



As mentioned in last year's Report, the transference of the Dunbar 

 Hatchery to the same site as the Marine Laboratory, Bay of Nigg, 

 Aberdeen, had to be postponed owing to delay in the completion of the 

 large tidal pond, and it was found necessary to continue the hatching 

 operations at Dunbar for another season. Owing to this and to the 

 stormy weather which prevailed during the early part of the year, the 

 collection of spawners was begun in the third week of February. The 

 fish were procured by the " Garland " from steam trawlers as in previous 

 years, and from February 25th to April 1st a total number of 419 male 

 and female plaice were landed and placed in the spawning pond. The 

 collection of the spawners was sometimes a matter of difficulty owing to 

 the stormy weather, and the " Garland " on several occasions found it 

 impossible to land the fish at Dunbar, and had to keep them on board, in 

 tubs, in Granton harbour until the weather moderated, a constant 

 circulation of water being maintained. On two or three occasions it was 

 found desirable to remove the ripe spawn from the fishes at Granton, to 

 fertilise the eggs, and take them on to the hatchery. It has been found 

 that, though in ripe condition at the time of capture, the plaice does not 

 spawn immediately upon being put into confinement. Several days, or 

 even more than a week, may elapse before the regular spawning 

 commences. But, as has been stated in previous Reports, this regular 

 spawning, or a daily production of fecundated eggs, is preceded by the 

 extrusion of non-fertilised eggs — eggs that have been retained in the 

 ovaries or oviduct so long that they are incapable of fecundation. This 

 retention of ripe eggs appears, in the first instance, to be due to fright, 

 discomfort, or bodily injury to the fish ; and if it is not continued for a 

 sufficiently long time to allow any quantity of ripe eggs to accumulate 

 has not serious consequences. Once the overdue eggs have been got rid 

 of a normal spawning follows ; but if a large number of eggs are 

 retained in the ovaries and oviduct the latter becomes congested, and 

 serious consequences for the fish may be apprehended. The as yet 

 healthy ovary continues to swell by the development of new eggs, and if 

 the outlet is closed it is easily seen how the ovaries may reach such a 

 distended condition as to be dangerous not only to this organ but to the 

 fish itself. The immediate consequences are that a fish in such a 

 condition becomes inactive, and does not take any food. If the capture 

 has inflicted any superficial injury in the region of the ovary, inflammation 

 soon sets in, and the tenacity of the abdomen becomes reduced. The 

 constantly increasing pressure in the ovary may gradually force a portion 

 of this organ through the inflamed tissue and leave it exposed. If, 

 however, the abdomen is healthy and able to withstand the ovarian 

 pressure, the intestines become pushed forward and partly out through 

 the anus ; while the foremost part of the oviduct is often also pushed 

 out externally. As in all these cases the fish is rendered useless for 

 breeding purposes, and almost invariably will die in the course of the 

 season, I have found it expedient at once to kill such specimens. In 



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