of the Fishery Board for Scotland. 



115 



Whether this is to be ascribed to a drifting of the mass of Copepoda from 

 one locality to another, or whether it is that the Copepoda in different 

 localities reproduce in succession and not simultaneously, or whether it is 

 owing to their having sunk to a lower level than 15 fathoms, is not easily 

 settled. In June, on Station I., the rapid increase seen during the 

 previous month was maintained, and the well-known condition of the water 

 of Lower Loch Fyne, as regards Copepoda, is attained. Brook,* in 

 noticing this fact, said — "Whether the myriads of Calani are bred in 

 Loch Fyne [Lower Loch Fyne is here referred to] or enter it in the 

 spring I have not determined. It is, however, a significant fact that 

 the herring enter Loch Fyne as the Crustacean becomes abundant, and 

 begin to leave it again as the stock gets exhausted. In July the number 

 of Calani decreases rapidly, and in September was reduced to that found 

 in the beginning of the year." The statements contained in the preced- 

 ing sentence are correct so far as they are used with reference to the 

 surface water ; but proof is wanting that they are true so far as the deep 

 waters are concerned. The herring does not usually enter Loch Fyne 

 until May. They are then to be found in Upper Loch Fyne, but 

 statistics are wanting at present which would serve to connect the move- 

 ments of the herring absolutely with the appearance of Copepods in 

 abundance. That the presence of the Copepoda is what attracts the 

 herring to Loch Fyne is probable. It might therefore be possible to in 

 some way announce the probable arrival, or perhaps to locate shoals of 

 herring by data afforded by an examination of the pelagic life of the 

 water. This has been done for the Baltic by the Norwegian observer 

 Hjort.f During the first month of the herring fishing in Loch Fyne 

 success is very slight indeed. Comparatively few herrings are in the 

 loch, and their capture is a mere lottery. An amplification of this plankton 

 work in Loch Fyne and other districts might afford important 

 results. Data of importance would be obtained, and these might in some 

 measure help to reduce the element of chance which governs the 

 herring fishing. 



In June all the stations except I. showed great diminution in the 

 number of Copepods, but in the following month the numbers increased at 

 the head of the loch (IV. and V.), and in the remaining three stations no 

 more Copepoda were obtained than in March. The diminution on 

 Station I. was excessively rapid. In August all the stations became still 

 poorer, and reached a stage in which Copepoda were practically altogether 

 absent from the surface down to 15 fathoms. Where the Copepoda went 

 to is a question of some importance. That they were drifted out of the 

 loch is not by any means probable. The reasonable explanation is that 

 they sink to lower depths. In August tow-nets were used on the 

 " Garland " at various depths down to 80 fathoms, and at 40 fathoms 

 Copepods were found to be abundant. There are in the present 

 research no data referring to greater depths than 15 fathoms, and so it is 

 not possible to say whether or not the same wealth of Copepoda did or 

 did not exist at the greater depths contemporaneously with the abundance 

 in the 15-fathom stratum. The question as to the depths at which 

 Copepoda and pelagic ova float will be treated later. 



On reference to the curves formed by the number of eggs, A and C, 

 Plate IV., we see that, as in the case of the Copepoda, there is a sudden 

 rise in April, but whereas in the case of the latter, Stations III. and IV. 

 were most concerned, Stations II. and V. were responsible for the increase 

 in eggs. Station IV. showed a very sudden decrease in Copepods in 



* Fourth Annual Report Fishery Board for Scotland, ]>. 47. 



f Hydrographic Biological Studies of the Norwegian Fisheries. Christiatiia, I89t!, 



