of the Fishery Board for Scotland. 



Ill 



little less than four miles, but still, during every month but July, Station 

 IV. was poorer to a remarkable degree than Station V. The distances 

 between Stations II. and III. and between HI. and IV. are eight and nine 

 miles respectively. These distances are comparatively small, and one 

 might have been led to expect that the strong tidal currents of Loch 

 Fyne would have effectually distributed the eggs over its whole area. 

 But that is not so. The question of the effect of the tidal current on the 

 eggs will be discussed later. In the North Sea Hensen asserts that there 

 is extremely little dispersion of the eggs ; that the eggs remain on the 

 whole very near the locality where they were extruded. In this reference 

 Hensen excepts areas near the shore, where there are local currents which 

 may tend to cause dispersion. If the eggs were equally spread over the 

 loch, the contents of the vertical net would bear a fixed ratio to the 

 contents of the horizontal nets for every station ; but this is not found to 

 be the case. In April, for example, the following numbers of eggs were 

 obtained for each station : — Station I., horizontal, 1625 eggs (vertical, 9 

 eggs); Station III., horizontal, 1150 (vertical, 127); Station IV., hori- 

 zontal, 663 eggs (vertical, 16) ; Station II., horizontal, 3297 eggs 

 (vertical, 54) ; Station V., horizontal, 2982 eggs (vertical, 52). A similar 

 want of relation between the numbers for the stations during the other 

 months can be seen on reference to Tables IV. to XL This fact 

 shows that even on one station the eggs are not equally distributed 

 as regards number ; and as the length of the station in that 

 month, April, was one quarter-mile, it is evident that the diversity and 

 variation in richness of different parts of the water are so great that no 

 practicable number of vertical hauls would be sufficient to give a correct 

 estimate of the numbers of ova present. A similar, though not quite so 

 marked, want of relation is to be seen also in the quantities of copepods 

 taken by the horizontal and vertical nets respectively. {Vide Tables 

 IV.-XI. 



In so far as Loch Fyne is concerned, then, the only method by which 

 even an approximate estimate of the number of eggs may be arrived 

 at is that of examination by means of horizontal towing. 



The calculated number of eggs which were floating in Loch Fyne at 

 the time of each visit is given in the vertical column marked " Grand 

 Total." The examination of the stations occupied one week each month, 

 and the number of eggs stated in the above column may be taken as 

 approximately representing, within necessarily wide limits, the 

 number of eggs in the loch during that week. There was an in- 

 terval of three weeks between the end of one trip and the beginning 

 of the next. During the interval eggs were spawned and hatched, 

 and it is by no means an easy matter to make an allowance for 

 them in the attempt to arrive at the total number of eggs which have 

 been there. One unknown factor, at least, has to be reckoned with, and 

 that is, Does spawning take place regularly or intermittently 1 We know 

 that for the individual spawning is intermittent, but how is the majority 

 of the spawning fish affected 1 ? Does the majority of the fish spawn 

 simultaneously, and simultaneously leave off spawning 1 ?; oris there during, 

 say, the main spawning month a somewhat similar number of ova 

 extruded daily 1 ? Another point to be considered is the length of 

 incubation. This is dependent on the temperature of the water. In 

 Table XVI. are given the temperatures of the water at the surface, 7 \ 

 and 15 fathoms, at the times of the different trips. During March, April, 

 May, and June the surface temperature varied from 6*5 to 14*4 deg. C. ; for 

 7 \ and 15 fathoms, the extremes were 7 -6 deg. and 10 deg. 8*5 deg. C. 

 may be taken as a rough average for the period of four months. At a 



