o/ the Fishery Board for Scotland. 123 



E. by K of the Spurn in the beginning of October was kindly sent by 

 Mr. James Gault, of the steam drifter " Sapphire," one of the deputation 

 of Elginshire fishermen who attended the demonstrations at the Laboratory 

 in April 1908. At the time the sea was very calm, and the water seemed 

 to be mixed with sand. On drawing a bucketful the water was seen to be 

 crowded with fry. They were still in the larval stage : a considerable part, 

 about a half in some cases, of the yolk still remained unabsorbed. The 

 herrings that were being caught then were in the spawning condition. A 

 shoal of herrings had evidently spawned on this ground some short 

 time previously. These larvae are on the whole bigger than those 

 hatched in September, and nearer the size of those of April. There may be 

 a material difference in the size of the eggs of different herrings, and this 

 circumstance may give rise to the variation in the size of the fry. Meyer 

 found that the summer fry of the Baltic herring were larger than the spring- 

 fry. 



The fry were put into various receptacles, viz., two tanks made of 

 concrete, with glass front and back, and hatching-boxes. The tanks 

 measured each five feet long by four feet wide by three feet deep. At first 

 the bottom of the tank was bare except for a thin coating of mud ; later on 

 it was covered with rough sand and small gravel. The hatching-boxes had 

 sand in them. They were usually kept floating ; the water circulated out- 

 side, but there was no direct current through them. All the tanks and 

 boxes were supplied with saud-filtered water. Some of the boxes had cooled 

 water. 



Plankton was put into the tanks, etc., from time to time. It consisted 

 principally of diatoms, solitary and in series. During March and April the 

 water near shore, from 5 to 7 fathoms deep, was, at the surface, much 

 richer in diatoms than was the sea five miles off the land, where the depth 

 was 30 fathoms and upwards. "When the plankton was poured in on one 

 occasion the fry swam about among it. It was hoped that the diatoms put 

 into the box would breed there. Colonies of algse grew in little bright green 

 spots on the glass panes. They consisted of spindle-shaped diatoms. A 

 brownish-green diatomaceous growth appeared over the bottom of the tank. 



The fry hatched from the uncooled spawn was put into the ordinary 

 water. The latter varied in temperature from 3-6° to 14'2° C. during the 

 period March 19 to May 19. The larvae of the cooled spawn was put 

 mainly into uncooled water, but some was kept in cooled water. The latter 

 varied in temperature from 1'4° to 10° C. 



The fry hatched from the cooled eggs were not always very active. They 

 were, however, observed on one occasion to be lively in water of the 

 following temperatures: — 1"4°, 2-1°, 2-3°, 2*5° C. Fairly cold water seems 

 to suit the larvse. 



The majority of the fry died soon. This was, I believe, due to injury 

 received in being driven about by the current of water in the hatching- 

 boxes. The others gradually died off. Some fry were still alive in one of 

 the tanks on May 6th. Many lived some time after the yolk was absorbed. 

 Some which were examined had no food in their stomachs, so far as could be 

 made out. 



The fry as they hatched out each day were distributed among the various 

 tanks, etc. It was not, therefore, possible to trace the batches of each date. 



At first the fry in the various receptacles seemed to do well, as they swam 

 actively about. A large number was put into one tank containing 2 feet of 

 water. As Ewart* described, the larvse swim vertically up to the surface of 

 the water and then allow themselves to drop some distance downwards, 

 which they do head first. Plaice larvse in the tanks were seen to swim 



* Op, cit. , p. 72, 



