Categories
vol-3BIOLOGICAL STUDIES ON SUDANESE INLAND FISHES
I Lates Niloticus
BY
A. A. AL-KHOLY*, s. Z.. ROFAIL ** A~D M. A. MABDI***
INTRODUCTION
Like any other living organisms fishes are affected hy certain physical
factors which limit their-distrihution. Of these variable factors, mountains,
thick forests, ,arid deserts, streches of water, as weB as temperature, chemi_
cal properties1of water, salinity, currents etc. are: among the conditions
which limit the wanderings of many fishes. ExtensitTe journeys are undertaken by fishes from one plaoe to another distant locolity. Spawning
or feeding migrations might take place regularly at c,ertain seasons of the
year (Norman, 1958).
When studying population or indiTidual species in relation to environmentaJ factors, it is necessary to take into consideration the nature of the
lifel cycle of the fish (Sverdrug et aI, 1955). By this mean the ul1der8tand~
ing of the hiological activities and the maintained race are made possihle.
The knowledge of reproduction, and the recognition of feeding and growing give the investigator valuahle means for the interpretation of population fluctuations. The understanding of the methods and routes of distribution are thus tr,aced. For this relason, a study Orf the growth, mainly length
and age relationship as well the suniyall l’Iates are caried out on some Nih~
fishes.
