PISCICULTURE 



197 



are well mixed with the milt, and the water 

 changed once or twice. The fecundation being 

 completed, the next thing is to place the eggs for 

 security into a covered vessel. Its early form was 

 that of a flat, round box about eight inches in 

 diameter, with a hinged lid. This was made of 

 zinc, perforated with small holes, and had a layer 

 of fine gravel on the bottom. A considerable 

 number of fecundated eggs were enclosed in the 

 box, which was then placed in the bed of a current 

 of pure water and covered with pebbles, care being 

 taken that the water passed freely through, as it is 

 necessary for the eggs to be slightly agitated. The 

 hatching takes place in from two to four months, 

 the time depending on the nature of the water and 

 other circumstances. For a description of the early 

 changes which the fish undergoes, see SALMON. 

 After the little fish are fully formed they are 

 kept in the box from ei^lit to fifteen days, and then 

 set at liberty. The later plans for artificially 

 propagating trout or salmon differ principally in 

 mixing the ova and milt in an absolutely dry uten- 

 sil and in the details of the hatching-boxes, in the 

 ii-ii.- of houses, and in many of the young fry being 

 kept in ponds till they are a year or more old. 



The most sustained! effort in British pisciculture 

 has been in connection with the salmon-fisheries of 

 the river Tay. At Stormontfield, near Perth, since 

 1853, a series of open-air breeding-boxes, covered 

 with gravel anil capable of receiving 600,000 eggs, 

 have Deen in use ; but for years nothing like this 

 number have been liatch'ed, and probably not 

 20,000 young lish annually have for some time past 

 been turned out of the ponds there. The Tay 

 District Fishery Board in 1883 erected a new 

 hatchery a few miles away at Dupplin on the Earn. 

 It was put np to try the system of glass grill hatch- 

 ing-boxes, designed prior to I860 by M. Coste of 

 I'iiris, and presently to lie described as in use at 

 Howietoun. On this pliin it was estimated to 

 hatch 300,000 ova. But in the autumn of !ss:i the 

 Board decided to adopt only partially the grill 

 hatching, and to try along with it the simpjer 

 Canadian system of shallow trays of perforated tin- 

 plate, and coated with Japan varnish ; in wliich the 



eggs, instead of being in separate rows, are packed 

 very closely together, river-water being used. In 

 1889 it was stated to be capable of hatching four 

 or five hundred thousand fish. 



The most extensive fish-rearing establishment in 

 Great Britain is the one belonging to Sir James 

 Maitland, situated at Howietoun, near Stirling. 

 It consists of hatching-bouses and, at a distance 

 from them of half a mile, an extensive series of 

 ponds. The principal hatchery is 86 feet long by 

 40 feet wide, each of its two stories being 10 feet 

 high. Its walls, built of brick and concrete, are 

 nearly 2 feet thick ; and the roof is covered with a 

 layer of concrete 3 inches thick, over which there 

 is a thin cover of asphalt. The entire outer shell is 

 thus a bad conductor of heat, so that it is not diffi- 

 cult to keep the water inside from falling below 44 t 

 F. Fig. 2 gives a sectional view of the hatchery. 

 It will be seen that each floor has a considerable 

 slope, which admits of the hatching or grill boxes 

 (a, a, a, a, fig. 2) being placed in descending series. 

 These are 134 in number, the ordinary size of them 

 l>eing 6 feet 9 inches long, by 1 foot 7 inches broad. 

 In the bottom of each box four wooden frames are 

 neatly fitted, each of wliich has rather more than 

 100 glass tubes, about J-inch in diameter, placed 

 transversely. Fig. 1 shows a longitudinal section 



Fig. 1. 



of one of these hatching- boxes, in which the dotted 

 line indicates the position of the glass tubes. Upon 

 these glass grills tne fish-eggs lie in parallel rows, 





looking like small pink beads. Six cisterns or 

 tanks (6, ft, 6), each 20 feet long and five feet 

 broad, are fitted up in the lower portion of the 

 ground-floor to receive the young fry after they 

 begin to take food. At Howietonn both hatching- 

 boxes and rearing-tanks are constructed of wood 

 charred on the internal surfaces, and painted on 

 the outside, their ends l>ein^ formed of perforated 

 zinc, which in closed with flannel when any depth 

 of water is required in the tanks. At other 

 hatcheries, however, the tanks and boxes are 

 formed of slate, and sometimes of earthenware, 



but in such cases they are of smaller size. Often, 

 too, the eggs are placed on perforated zinc or porous 

 earthenware instead of glass grills. While the 

 eggs are being hatched only spring water is used. 

 It is brought underground to the two cisterns 

 (c, c), and from these it is conveyed by lead pipes 

 (p,p,p,p) to each series of hatching-boxes, over the 

 grills of which it flows in a constant but not rapid 

 stream. Each of the hatching- boxes contains 

 H.IIHIII 15,000 eggs, but in the earlier part of the 



hatching-season (December) eggs are also placed in 

 20-feet tanks, so that about four millions of 



the 20-1 



