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Part III — Seventeenth Annual Report 



" the ebb stream lasts about one hour longer than the flood, a given 

 " particle of water on the surface would be carried one mile down the 

 "loch by each tide, supposing the weather calm." He states that " the 

 " tidal current, according to the Admiralty publications, enters Loch Fyne 

 " at Otter at the rate of 3J knots, passes through the Gortans Basin at 

 " 2 knots, increasing to 2 J at Minard Narrows, but then slackening until, 

 " off Dunderawe, near the head of the loch, it is reduced to 1 knot." 

 In 1896 (8th September) the result of observations made by Mill* on the 

 tidal current at Otter gave a rate of about f-knot an hour for the last half 

 of the flood, and about 1 knot an hour for the ebb. " A great 

 "accession of fresh water on the surface must necessarily, by raising 

 " the level, accelerate the ebb tide. ... On the other hand, after a 

 "long dry spell, the tendency of evaporation would be to lower the 

 " general level, and so accelerate the flood tide." 



In the absence of sufficient data bearing upon the tidal currents over 

 the whole loch, it is not possible to effectively discuss the effects which 

 these currents have on the distribution of the pelagic eggs. It is 

 very clear, however, that, from the rate of the current in the Gortans 

 basin and at Otter, a large proportion of the eggs floating at Station II. 

 will probably be carried out into Lower Loch Fyne with each ebb. From 

 Station III. those eggs at least which were close to the surface would be 

 subject to drift, and should in a few days arrive at Otter. From Stations 

 IV. and V., however, taking the drift down the loch at the average of 

 1 knot per day, the eggs would be hatched long ere they reached the 

 Gortans basin. The surface eggs would be all subject to the drift, but 

 how far any eggs floating at some depth below the surface would be 

 affected only further investigations can determine. It is at least evident 

 that those eggs which vary by having a specific gravity a little less than 

 the average will be first acted on by surface currents, and so the variation 

 in specific gravity in the eggs of a species has an important bearing upon 

 their distribution. It may at least be confidently stated that a large 

 number of eggs spawned in Upper Loch Fyne go to enrich the waters of 

 the lower loch. It must, however, be borne in mind that the spawning 

 of the fishes in Loch Fyne has been inferred only from the presenee of 

 their floating eggs there, and not from an examination of the fishes them- 

 selves. From the fact that large numbers of eggs in the later stages of 

 development were found on Station II., it might be inferred that they had 

 drifted there from regions further up or further down the loch. Murray 

 has shown that the winds are important factors in the formation of 

 currents. t He has shown for Loch Fyne that a strong southerly wind will 

 heap up the surface waters at the head of the loch, while the place of the 

 water transported from regions further down the loch is partly supplied 

 by the upwelling of water from below. Strong southerly winds, as well 

 as flood tide, may carry into Loch Fyne the ova which are floating 

 outside, and so two causes might be cited for the occurrence of large 

 numbers of advanced eggs at Station II. — viz., (1) a drift down the loch 

 through currents due to northerly winds and the ebb tide, and (2) trans- 

 port of eggs from the lower loch into the upper loch by currents induced 

 by southerly winds and the flood tide. % 



The Copepoda will also be subject to the various currents, but, from the 

 fact that they on the average float at greater depths than the eggs, their 

 drift must be slower. It is not, therefore, probable that the 

 presence of vast numbers of young Copepods on the low r er stations, subse- 

 quent to their appearance at the head of the loch, is in any important 

 respect due to drift. 



* Fifteenth Annual Report of the Fishery Board, Part III., p. 270. 



f Murray. " The Effects of Winds on the Distribution of Temperature in Sea- and 

 Fresh-Water Lochs of the West Coast of Scotland." The Scottish Geographical Magazine, 

 July 1888. 



J Vide in this connection Petersen. " Pelagic Life of Faeno Sound." Copenhagen, 189'?. 



