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Part III, — Fifteenth Annual Report 



excepted), and the greatest number occur east of May Island, and in 

 Station II. In June, advanced eggs are found scattered over the whole area, 

 from Cross-section III. to Station IX. The numbers of eggs spawned 

 gradually increase through April, and attain a maximum in May, and tail 

 off in June. Such items as ' 191,' ' 249,' ' great numbers,' appear at the 

 end of April and beginning of May, and mark out this period as the time 

 when the greatest amount of spawning takes place. There can be no 

 doubt, from what we have remarked, that flounders spawn all over the 

 Firth of Forth area below Inchkeitb, and there is no indication to lead us 

 to suppose that spawning begins any earlier in one part than in the other. 



No doubt the eggs spawned in March and early April in the outer 

 stations undergo the same drift inwards as in the case of the cod and 

 haddock, and those in the inner stations will also steadily drift, apart from 

 tidal fluctuations, westwards up the Firth. The egg of the flounder is 

 minute, and takes less than seven days to develop at 6 - G° C, a mean for 

 tli9 Firth of Forth during mid-April, so that it is enabled to be laid 

 further inshore than that of the cod or haddock, and still more so than 

 that of the plaice, and this is accentuated still more by the fact that the 

 temperature of some of the inner stations may rise to so high as 8*3° C, at 

 which temperature the egg of the flounder would hatch in about five days. 

 In mid- May the mean temperature of all the stations, I.-YIII. inclusive, 

 for 1893, was 10° C, at which the hatching-period of the flounder would be 

 further reduced to four and a half days, so that, taking further into con- 

 sideration the fact that the winds are neither so persistently ' east,' nor so 

 violent when the summer approaches, and we can see how a species like the 

 flounder, with a small egg and a comparatively late spawning-season, can 

 spawn inshore with comparative impunity though a fecundity which is 

 the highest for its size amongst food- fishes, tells a tale of loss amongst the 

 young stages from which the plaice is comparatively immure, and the cod, 

 to a lesser extent. In June, the temperature may rise as high as 14'6° C. 

 (Station IV., 1893), at which the flounder's egg will probably hatch in a 

 period under three days, thereby greatly reducing the time to which it is 

 exposed to the freaks of wind and weather. 



One other consideration is worth noting, taking the flounder as a type 

 of a diffusely-spawned egg in a rather late season of the year. As the 

 spring terminates, and the summer approaches, it is found that the tem- 

 peratures of the different stations differ widely, and in this way that the 

 temperature of the inner stations becomes higher than that of the outer. 

 Thus, in 1892, the mean temperature for the end of May 1892 was in the 

 inner stations (Stations I., II., III., and IV.) 7 '9° C; in the middle 

 stations (Stations V., VI., and VII.) 7 "5° C; and for the outer stations 

 (Stations IV., VIII., and IX.) 7'4° C. The difference in this month is, 

 although perceptible, not very marked, and possibly falls within the error 

 due to reading at different times in the clay. On the other hand, in June, 

 the difference becomes more pronounced. The mean temperature of the 

 four inner stations (taken between 10 a.m. and 2 p.m.) is 11° C, that of 

 the middle stations is 9*8° C, and the two outer station?, 9 9° C. The 

 inner stations certaiuly have a higher temperature of about 1° C, and the 

 same difference is shown in July. The differences are probably much 

 greater some way below the surface, the usual position of pelagic eggs. 

 At anyrate, these differences will all tend to make the eggs, laid further in- 

 shore, have a more rapid incubatory period, and will thus help to nullify 

 the dangers of deposition of spawn near inshore. The nearer inshore the 

 flounder spawns, the closer approach is there of the spawning-area to the 

 habitat of the adult. 



