252 ^- S- WiMPENNY 



are some observations on the age, length and weight composition from samples of the 

 commercial catch. The age, length and weight data for 1930, 1931 and 1933 are 

 published here for the first time. On this basis therefore and, as far as the data 

 permits, it is proposed to follow the annual production of Tobar in Lake Mariut 

 for the first fifteen years after its introduction, and to examine the changes revealed, 

 paying special attention to the years 1928-31 and 1933. 



\)— ^--o^ • ^^^*^ 



O CATCH PER BOAT 



N? Of BOATS 



(IOC*) - 



- kg 

 200H 



to- 



I50H 

 ICO 

 5- 50^ 



O LAHE LEVEL 



• CATCH ^ 



200- 2-80 



tons ~ 



- 2 90 

 I50- 



^Ci - 300 



\ 



\ lOO- 



\ 



- 3IO 



\ 





J L 



FRY IN MILLIONS 

 5- 



2- 



I- 



3 4 



Fig. 1 



Relation of fry to catch 



The relation of fry introduced each year to the corresponding catch is shown in 

 Fig. 1. In a general way the fry introductions built up parallel to the catch until 1927, 

 and thereafter fell away to lower levels in the thirties. There are, however, two years, 

 1921 and 1930 in which the unusually high values of 28-6 and 51-1 millions are 



