50 



Appendices to Fifth Annual Report 



Aberdeen bays in the same manner, next describe shortly the work that 

 has been accomplished since the passing of the Eye-law. 



Sufficient time has not yet elapsed since the passing of the bye-law to 

 admit of definite conclusions being arrived at. In the present Report it 

 would therefore be premature to discuss at length the results likely to 

 follow the prohibition of trawling in the territorial waters. As the 

 experiments will require to extend over several years, the public interest 

 will be best served if in the meantime we indicate generally the physical 

 and biological conditions of the Forth and St Andrews Bay, as far as 

 they have been ascertained, and append the statistics collected, which are 

 likely to assist in throwing light on the influence of trawling and other 

 modes of fishing in diminishing the number of fish in the territorial 

 waters. 



Physical Conditions of the Firth of Forth. 



From the investigations recently made by Mr Hugh R. Mill,* 'it seems 

 ' the Firth of Forth may be described as extending from Alloa to the Isle 

 ' of May. From Grangemouth to near Queensferry it averages 1J miles in 

 ' breadth, with a depth of less than 10 fathoms ; at Queensferry it contracts 



* to 1 mile, and the depth increases to over 40 fathoms, but diminishes af ter- 



* wards. From Queensferry the breadth increases to 5 miles at Leith 

 1 and 16 at Musselburgh, contracts to 8 miles at North Berwick, and again 

 ' widens, measuring 18 miles across where it merges w 7 itb the North Sea 



* at the Isle of May. The deep water at Queensferry is confined to a 

 ' very small area, and the 10 fathom stream, broken by a few deeper 

 ' patches, runs along the northern shore to near Kirkcaldy, where it widens 

 ' out in a funnel shape (see chart, Plate XX.). A short tack of over 10 

 1 fathoms, known as the Narrow Deep, lies to the south of Inchkeith, and 

 ' a few miles to the east of that island the 20 fathom area begins as a 

 ' narrow stream, tending north-eastwards, and spreading out off Largo 

 ' towards both shores. The Isle of May is connected to the mainland of 



* Fife by a submarine plateau rising to less than 20 fathoms from the 

 ' surface, and a few miles to the eastward of it depths of over 30 fathoms 

 ' commence. The mean depth of the whole Firth is 14 fathoms, the greatest 

 ' extent of shallow water being the range from Leith to North Berwick 



* along the south shore across Aberlady Bay.' 



In considering firths into which a large river enters at the one end while 

 the other is in free communication with the open sea, the saltness of the 

 water is of great importance in influencing the movements of the fish and 

 their food, and also the development of both ova and young fish. From 

 the observations made it seems that the salinity of the surface water in- 

 creases rapidly from the river to Queensferry, while from Queensferry to 

 Inchkeith the rate of increase is more gradual and the tidal difference less. 

 From Inchkeith to the Isle of May the rate of increase in salinity is 

 very slight, and the tidal variation almost imperceptible. 



Inquiries as to bottom salinity show that tidal change extends only from 

 the river to a point off Blackness, and the rate of change is everywhere 

 similar to that for surface salinity, but more uniform. As far as Inchkeith 

 ' surface salinity is always less than that at the bottom, but gradually 



* approaches it, and seaward of Inchkeith the surface water is scarcely at all 



* fresher than that beneath, until some little distance beyond the mouth of 



* the Firth, where the freshening action of the Tay appears superficially, but 

 1 is not felt at a depth greater than about 5 fathoms. Between Inchkeith 



* The Physical Conditions of the Firth of Forth, by Hugh R. Mill, D.Sc, page 349. 



