of the Fishery Board for Scotland. o41 



The first series is, as a rule, quite sharply separated from the 

 second series, especially in summer (PI. XIVa.), the coalescence or over- 

 lapping exhibited by older groups being absent. 



The averages shown in the above Table caiuiot, however, be 

 regarded as accurate, especially in the months immediately following 

 the spawning season, because great numbers of the young plaice are 

 then too small to be captured with the net, and the average indicates 

 not the mean size of the series at the time, but the mean size of those 

 taken by the net, i.e. of the larger individuals. It will be observed 

 that, with the exception of June, the minimum size of those taken in 

 all the months ranges from only 39 to 45 mm. We know, however, 

 that much smaller plaice inhabit the beaches than these. Dr. Kyle, 

 in the paper previously referred to,* shows that post-larval plaice may be 

 taken in considerable numbers in June and even in July, August, and 

 Se[)tember ; in the latter months, however, they must be relatively few. 

 In the push-net collections above referred to plaice from 12 mm. were 

 obtained at the end of June and beginning of July, while at the end 

 of the month the minimum size was 18 mm. ; at the end of August the 

 smallest was 34 mm., but since specimens this size and 33 mm. were 

 taken in November, the minimum size is probably less at this time. 

 In order to reduce the computed avei-ages to a better standard, I have 

 taken the ascertained maximum size of the series as one limit, and 

 have assumed as the minimum sizes in the various months the 

 following, viz.: — June, 14mm.; 30th July, 18mm.; 30th August, 

 25 mm. ; 28th September, 30 nun. ; October, November, and December, 

 32 mm. ; March 35 mm. ; and April, 40 mm. 



The series of the year, derived fi'om eggs spawned in spring, was first 

 collected in June, no haul being made in May in the shallow water. 

 On the 29th June the range of the 180 specimens was from 29 to 57 mm., 

 the apparent average size being 40"6mm., or 1^ inches. An examina- 

 tion of the curve, however (PL XIVa.), shows, as stated, that the smaller 

 fishes must have escaped in numbers from the net, and that the mean 

 size at this period is about 35 or 36 mm., and the range from 12 or 14 to 

 57 mm. A month later, on 30th July, the mean size was 54"0 mm., 

 showing an apparent growth of 13*4 mm. in the month; on 30th August, 

 when the curve indicated that the series was more nearly uniformly 

 represented, the average size was 58"3 mm., a total increase of 17*7 mm. 

 in the two months. From this period until the end of November 

 growth in these small plaice was practically in abeyance. The averages 

 for this series in the various hauls in the previous year — 1899 — were 

 somewhat lower, and are not so uniform, but the series was pretty uni- 

 formly represented in each haul, as shown by the curves. It will be 

 observed that plaice as small as 43 and 45 mm. were actually taken 

 in the shrimp net in March and April, when they must be very 

 nearly a year old. 



These averages may be examined more closely. The size of the 

 plaice newly settled on the bottom, about the middle of- May, was, we 

 have seen, about 12 or 13 mm., and the average size on 29th June 

 was (as corrected) 35 or 36 mm. The young plaice have thus increased 

 in length in the interval of forty or forty-'five days by about 22 mm., 

 that is to say by very nearly threefold. This appears to be the period 

 of relatively most rapid growth during its life, and it coincides with 

 the period, as we shall immediately see, when the rise of temperature 

 of the shallow water on the beaches is greatest. At the end of July, 

 thirty-five days later, the average increase amounted to 13-4 mm., the 



* SixleeiUli Ann. Rejyort FUhery Board for Scotland, iii., p. 239. 



