of the Fishery Board for Scotland. 



165 



Sprats and immature herring are amongst the must timid and restless 

 of all fishes. They swim usually in separate shoals, but in the estuary of 

 the Tay, where the main channel is so shallow and narrow, they very 

 often mix and swim together. 



Hardly any two fish in the sea have so many and varied enemies as 

 the sprat and herring. This incessant persecution by numerous enemies, 

 and consequent restlessness, may possibly partially account for the pre- 

 sence of both fish in such large numbers in the estuaries of rivers. 



The fishermen, in trying to explain the presence of the fish in such 

 large numbers in the Tay estuary, believe that the sprat and herring 

 have a liking for brackish waters, and some scientists are under the 

 impression that the fish seek the colder waters. 



Several] considerations, however, seem to be against such ideas. Both 

 fish, while in the estuary, appear to remain in the main tidal currents, 

 where the water is somewhat warmer than the surrounding waters. 

 Experiments also show that in very cold waters fishes give up feeding 

 altogether, probably because the ferments upon which digestion depends 

 do not act, or at any rate very slowly. 



The fishermen also believe that the fish ascend the estuary to feed on 

 the small organisms in the water, but this is also more or less erroneous. 

 The majority of the herrings' stomachs examined were found to be empty ; 

 only a few contained a very small quantity of Crustacea, while the sprats' 

 stomachs were invariably found to be quite empty. Moreover, in the 

 river at this season, the fish would get little or no food material to 

 swallow, as careful examination of samples of water have shown. 



Fishermen are also of opinion that the state of the tides is related to 

 the quantity of fish in the river, that during spring tides the fish are 

 more plentiful than during neap tides ; but after carefully comparing the 

 daily catches with the state of the tide, I am unable to show a close con- 

 nection. Certainly on several occasions the best fishing was at or near 

 the spring tides, e.g., November 23, December 7 and 22, and January 

 17-21 ; but there was fairly good fishing during neap tides about Novem- 

 ber 1 and 15, December 27, and very good about January 12. 



They, again, believe that rough weather, especially strong south-easterly 

 gales, drive the fish into the river, but this also I am unable to prove. 



During the great scarcity of fish in the month of November, I 

 questioned many of the fishermen as to the state of the water in the 

 river. Ond and all believed that they had never seen such a lot 

 of fire (phosphorescence) in the river as during that time. This 

 phosphorescence, along with the clearness of the water, enabled 

 the fish to see the nets and thus avoid them. This I believe to be 

 partially true, for if the fish swim in small, narrow, separate shoals, as they 

 appear to do when not very plentiful in the river, then they might 

 conceivably take fright at the glowing anchor and the chain, &c, and 

 thus at the same time swim clear of the open mouth of the bag-net. 

 Against this idea, however, is the fact that very seldom were the nets 

 brought up absolutely empty, while nearly every boat managed to 

 capture from J to 3 crans of fish. During the daytime, however, it is a 

 fact that little or no fish are caught if the water is very clear and the fish 

 not very plentiful in the river. The fish avoid the light and swim at a 

 much lower level, and thus avoid the open mouth of the bag-net. 



