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Part III. — Fifteenth Annual Report 



inclosed basin of the Forth, as examined at Stations I., II., III., and IV., 

 and Cross-section III., is as late as March 21st in 1890, as March 30th in 

 1891, April 16th in 1892, April 18th in 1893, April 16th in 1894, and 

 April 18th in 1895. In every case in which the stage of development 

 is registered, the eggs found in these stations were at an advanced stage 

 of development. During' April and May, the eggs are found in small 

 numbers dotted throughout the Firth, and in the outer stations as well. 

 The last two appearances are in the outer stations, and a single specimen 

 in June at Inchkeith completes the series. 



These facts, although more clearly demonstrable by diagrams showing 

 the distribution at each month, are sufficiently clear in their significance 

 to point out that the eggs are laid from the early part of February on- 

 wards in the outer stations, east of the May Island ; that these eggs are 

 in part drifted in by the currents, as described in detail under the heading 

 of the cod, in part carried elsewhere • that, as the season advances, the 

 eggs become dotted about the Firth in more widely distributed numbers, 

 and that in the outer stations the supply of freshly-spawned eggs, after 

 reaching a maximum in about mid-March, tails off slowly till about the 

 middle of May. From mid-February to mid-May is a period of three 

 months, far exceeding the duration of the incubatory period, so it happens 

 that it would be almost possible, by taking a series of hauls at different 

 stations from without inwards, at a given date in the middle of the 

 spawning-period, to obtain a series of stages from the eggs to the hatching 

 stage. The next consideration i^ that the number of eggs, either in the 

 outer or inner stations, are not nearly as great as should be the case for 

 so common a species. Examination of the areas beyond Station IX., 

 such as Liston Bank, and further north towards the Bell Rock, show that 

 the main spawning-areas of the plaice are, in these places, further out 

 from the shore. We may conjecture, from present knowledge, as in the 

 case of the cod and haddock, that the Firth of Forth probably depends 

 for its supply of floating eggs upon the section of eggs which are spawned 

 within a few miles of the Isle of May. This applies still more to the 

 plaice ; and the comparative scarcity of the eggs of the plaice is probably 

 to be accounted for by the tendency for the plaice to spawn further sea- 

 wards. The plaice spawns at a markedly earlier period than the haddock 

 or cod, and, in accordance with this, and with the fact that the egg is 

 larger, the average incubatory period must be longer. This demands a 

 spawning-area further out from the shore. 



We thus note that (1) the spawning-areas of the plaice are well off- 

 shore, the nearest to the Firth of Forth being in Station IX., and in some 

 degree Station VIII.; they do not extend into the Firth. (2) The spawn- 

 ing-season commences (for the Firth of Forth) in the early part of 

 February, increases in the number of eggs spawned till April, and de- 

 creases through May. It is only very exceptional to find eggs of the plaice 

 as late as June. (3) The distribution of the eggs after spawning is similar 

 to that of the cod and haddock, but as the plaice, as a whole, spawn 

 further out, fewer eggs of plaice are drifted into the Firth. These con- 

 clusions bear out in a remarkable degree those arrived at by Professor 

 MTntosh in the Trawling Report, and Dr Fulton, who both examined 

 spawning plaice and their distribution. 



TABLE V.-EGGS OF FLOUNDER. 



FlKTH OF FORTH. 



Mar. 6, 1895. Station VIII., 

 „ 16, 1894. Largo Bay, . 

 „ 16, 1892. Station IX., . 



27. 



30. 



57 (dab and flounder). 



