— 7 



APPENDIX H' ; REDEKE 



Ripe females of this group were only taken in a few instances. We cauglit some 

 which had a length of 25 cm.; these were quite the smallest ripe females which have 

 as yet fallen into our hands. The majority had a length of 30 to 32 cm. and were in 

 the beginning of their fifth year. 



I may remark incidentally, that these results confirm Kyle's observations, which 

 likewise indicate, as is well-known, that the male plaice are in general mature a year 

 earlier than the females. 



If we return to the Ill-group, we see that the fish of this group constitute the main 

 portion of the plaice on our most important fishing-grounds in spring, and that among 

 these there is a relatively considerable number of mature males. 



At this age, it is extremely difficult to ascertain the average size of the plaice, quite 

 apart from sexual differences which are very important from the third year on. In this 

 group, the phenomenon al- 

 ready often mentioned is 

 specially well-marked , na- 

 mely, that the individuals 

 of the same age are larger 

 the further they are taken 

 from the coast. 



In March 1904, for ex- 

 ample, plaice of the Ill-group 

 taken atVlieland were mostly 

 19 to 21 cm. long, those on 

 the Broad Fourteens 23 to 

 25 cm.; again, in June, those 

 taken near the coast were 

 21 to 22 cm., those in the 

 central part of the region 

 25 to 27 cm. In September, 



19 20 21 22 23 H 25 26 27 28 29 30 31 32 33 34 35Ceohn). 

 Fig. 2 



Percentage frequency-polygons of two hauls of plaice made on the Brown 

 Ridges. — The continuous line refers to a haul made in spring (June '04) 

 this group has almost en- ^„j consisting chiefly of the Ill-group, the broken line refers to a haul 

 tirely disappeared from the made in autumn (Nov. '03) and consisting chiefly of the Il-group. 

 coast; those taken in the 



open sea varied greatly in length, as the catches consisted chiefly of a mixture of the 

 Il-group and small specimens of the Ill-group, obviously late migrants during the summer. 

 In addition, larger specimens of the Ill-group (up to 31 cm.) also occurred. 



In November, lastly, it is only in the hauls in the central part of the North Sea, 

 that the Ill-group occurs somewhat abundantly. It is replaced everywhere, however, by 

 the Il-group, which at this time is distributed over the whole region. 



The female plaice have now also reached the age when the majority are ripe for 

 the first time. How large their number is and the proportion of males in this group, 

 have not as yet been definitely determined and must remain uncertain for the time being. 



The plaice belong now to the IV-group, i. e. they are at the beginning of their fifth ,]^fpP'^"'"J^^ 

 year. From this time on, when the size of the majority lies between 25 and 35 cm., 

 they suddenly become comparatively scarce. Plaice of the IV-, V-, VI- etc. groups belong 

 in general to the rare occurrences in the hauls on our coast and are taken almost ex- 



