of fh It Fisher If Board for Scotland. 



:]83 



The periods do not quite correspond, and that for the northern part 

 of the North Sea includes a lai-ge part of May, a more favourable month 

 for growth, but they serve to indicate a more rapid growth of the 

 long i-ough dab in autumn and winter on the East Coast than in the 

 Clyde, and the average size of the series at corresponding dates indicates 

 the same thing. Thus at the end of August the mean size on the 

 Clyde was 43'5 mm., compared with 48-3 mm. ofl'the Shetlands and 

 53-0 mm. oft" Aberdeen ; in October the Clyde average was 49'0 mm., 

 while it was in that month 53*3 off the Shetlands ; in December 

 the Clyde average was 52'8 mm., compared with 65*5 mm. oft' Aberdeen. 

 The causes of this diftei'ence are not clear, but the more tardy growth of 

 the first series on the Clyde within the considerable part of the year 

 referred to would suggest a smaller annual increment and tardy 

 growth in the next larger series. Such is found to be the case, and 

 it at first caused a little mystification. It is well shown in some of 

 the curves (PI. XIX,). 



Considering the next older series or generation, the haul on 30th 

 August yielded ninety-nine specimens from 65 to 87 mm. in 

 length, and with an average size of 77"6 mm., or 3yL. inches. On the 

 presumption that the rate of growth in the two periods was .similar, 

 the difference between the average for April and this avearge would 

 indicate the amount of growth in summer, viz. from 3rd April to 

 the end of August, a period of 150 days, and the diflference i.s 

 22' 1 mm. If the ascertained growth in the remainder of the year, 

 from 30th August to 3rd April, given above, be added to this — namely, 

 120 mm. — it indicates an annual increment at this .stage of about 

 34 mm., which closely coi-responds to the increment deduced from 

 comparison of the average size of the annual groups or series at a 

 given date. 



The particulars of the second sei^ies in the various hauls are as 

 follow : — On 1st August twenty were taken with an average size of 

 765 mm., and a range from. 67 to 88 mm. On 30th August the 

 average for the ninety-nine specimens of both sexes w-as, as we have 

 seen, 77"6 mm., and the range G5 to 87 mm. On 14tli September the 

 range of thirty-six specimens, of both sexes, was from 62 to 91 mm., 

 and the average size 77 6 mm.; twenty-one were females averaging 



