of the Fishery Board for Scotland. 



11.9 



daylight and comes to the surface at night. But as all the experiments 

 were carried out in Loch Fyne during the day, such a reason would not 

 agree with the fact that a considerable proportion of the Copepoda 

 was found at the surface on several stations in January, February, and 

 March, and at Station III. in April, and at Station II. in July. Varia- 

 tions similar to those seen in the figures for the egg collections are to be 

 seen in those of the Copepods. In many cases the figures take a spindle 

 shape, tapering upwards and down from the level where the majority is 

 floating, which at Station I., May, and Station IV., June, is at six 

 fathoms. We have also barren intermediate regions represented, viz., at 

 six fathoms on Station II., March, and at ten fathoms Station V., July. 

 On the whole, however, the Copepod figures are more regularly spindle- 

 shaped than the egg figures. The amount of vertical dispersion is 

 greatest in January, February, and March, and in July and August, 

 while during April, May, and June the Copepoda in the 15-fathom 

 stratum are on most of the stations concentrated at a depth of four to six 

 fathoms. This concentration coincides with an increase in the salinity of 

 the water. In August the Copepods had almost entirely disappeared from 

 the 15-fathom stratum at Stations I. and II. On Station I. the seven 

 horizontal nets produced 39 Copepods ; at Station II. 41 Copepods were 

 taken at 15 fathoms; and 8 Copepods in the remaining six nets. A few 

 Copepods were found at Station III. from four fathoms down, and on 

 Station IV. four individuals were captured at the surface. At fifteen 

 fathoms they were fairly numerous. Station V. furnished the largest 

 number of Copepods, but they were in small quantity. The figure which 

 is introduced into the Table for that station is greatly exaggerated in 

 order to bring out the relations of the quantities at different depths. On 

 the whole, the centre of suspension for Copepoda is lower than that of the 

 eggs. The close association of pelagic eggs with Copepods results in their 

 being eaten by the herring. Brook found pelagic eggs in the stomach of 

 that fish. 



Note. — In the preparation of the figures in Plate V. an allowance is 

 made for the fact that the nets, in sinking to the depth at which they are 

 intended to fish, capture a certain number of eggs and Copepods. They 

 fish also while being hauled to the surface. The nets the takes of which 

 would be most affected by this fact are the 10 and 15 fathoms nets, and 

 since the area of the mouth of one of the horizontal nets is very nearly 

 equal to half the area of the vertical net, the collection taken in the 

 vertical net on the station is regarded as approximately equal to what the 

 horizontal net captures in its downward and upward journeys. This 

 quantity is therefore subtracted from the takes of the 10 and 15 fathoms 

 nets on each station. 



On the Drift of the Eggs. 



Fulton's * investigations in connection with the currents of the North 

 Sea, while resulting in the determination of the direction and rates of the 

 surface currents, have so far not resulted in proving the depth of these 

 currents. In Loch Fyne, according to Mill, t " the tidal current is not 

 "merely superficial. That the tide sweeps across at Otter to its full 

 " depth is proved from salinity observations. . . . The current of ebb 

 " tide evidently affects the water to a considerable depth, at any rate in 

 " the Gortans basin. ... An average velocity of 1 knot for the 

 "surface current appears from the Admiralty charts to be the maximum 

 " estimate of the surface tidal currents in Loch Fyne. At that rate, since 



*"On the Currents of the North Sea.," Fifteenth Annual Report Fishery Board for 

 Scotland, Part III., p. 270. 

 f Clyde Area (op. cit.). 



