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Part III. — Fifteenth Annual Report 



all over the Forth area, pretty evenly distributed. The same remark 

 applies to the month of May, though in the latter part of this month the 

 numbers tail off in the outer stations. Through June, the hauls con- 

 taining dab's eggs are almost confined to the inner stations, with only one 

 observation on the 2nd in Station IX., and a couple of eggs in Station 

 VIII. Those in July and August are only isolated examples, three hauls 

 in 1892 giving an aggregate of 7 eggs in the former, and one haul in 

 1895 giving four eggs in the latter. 



The spawning-period of the dab may be thus considered in an average 

 year to extend over the months of March, April, May, June, and July. 

 This agrees with Dr Fulton's estimate of 'end of February to July, 

 but ordinarily in April, May, and June.' As regards the spawning-areas, 

 all appearances point to the fact that the dab spawns all over the Firth of 

 Forth area, and that there is very little segregation for the purpose of 

 spawning ; the small numbers, at early stages, occurring at every station 

 of the Forth, can indicate nothing but this fact. At the same time, there 

 are clear indications that the dab commences spawning in the outer 

 stations at an earlier period than in the middle, and still earlier than in 

 the inner; and it cannot be doubted that the eggs of the dab, spawned in 

 March and early April in the outer stations, are drifted inwards, under 

 the prevalent east winds, as in the case of the cod, haddock, and plaice. 

 Thus, in 1891, the eggs first occur (in February 19th) in Station VIIL, 

 and the next are a month later in Station V. In 1892, the first recorded 

 dab's eggs are as late as April 4th, several miles east of May Island, 

 followed by Cross-section II. (on the 8th) and Cross-section III. (on 

 the 11th). In 1893, no dab's eggs are recorded till April 14th, when 

 a few are found in Station IX. In 1894, there are very few records, and 

 none whatever in Stations VIII. and IX. Lastly, in 1895, the first 

 occurrence is on March 6th in Station VIIL, and the next at Stations 

 VIIL and IX., the middle and inner stations not being represented till 

 the 5th of April and the 18th of April respectively. With the exception 

 of the rockling, the egg of the dab is the smallest of the pelagic eggs 

 here dealt with, and its period of incubation is probably very short. 

 We are thus met with a difficulty in that, if the egg of a dab be spawned 

 in the end of March, and in an outer station, alongside that of a cod, then 

 if the drift-currents are of the right force for the cod's egg, and it 

 reaches the shallow water at the assumption of the post-larval period, then 

 the egg of the dab will be too precocious, and the post-larval form will 

 require to seek the bottom long before the shallow water is reached. 

 This difficulty is probably overcome by the fact that the Forth area is, 

 comparatively speaking, shallow water all over, and that, therefore, the 

 young dab can migrate downwards to the bottom as soon as it is able to 

 do so, and find a suitable habitat at the bottom of the Firth. 



On account of this conformation of the Firth, the eggs of all the fishes 

 we have referred to have not to guard, to any great extent, against any too 

 early development ; the main danger is a * deferred ' development, and 

 1 beaching ' as a result. This greatly reduces the mortality amongst the 

 eggs and larvse, and is probably the main reason why comparatively 

 shallow firths should be used by the food-fishes as nurseries. Were there 

 deep water close inshore we should certainly expect the egg of the dab to 

 be spawned, if contemporaneously, closer inshore than that of e.g. the cod. 



The eggs continue to be found in small numbers in the outer stations in 

 April and May, and these are probably spawned on the spot. The few r 

 occurring in June have most likely been spawned in stations further in- 

 shore, and have floated outwards (cf. Sprat). In the middle stations, 

 spawning commenced in the middle of March, and the greatest number 



