Cichlid fish species dominating in Rosetta Branch of the River Nile were studied.
They were collected from the commercial catches of widespread used trammel nets during
2008-2009. Analysis of the species composition revealed that Oreochromis niloticus
dominated the tilapia catch followed by Oreochromis aureus and Tilapia zillii. The lengthfrequency
of the dominated O. niloticus varied between 11 and 27 cm total length and its
length weight relationship was W = 0.023966 L2.92209. The selection range as deduced
from the probability of capture varied according to the mesh size used of the inner layer of
the net The selection factor corresponding to the compared two different mesh sized nets,
that widely used, was also estimated. The results indicated that the mean selection length
should be increased to reach at least 15cm by increasing the mesh size of the inner layer of
trammel nets to 60 mm stretched mesh or 30 mm mesh bar. This will lead to increasing
the average weight of O. niloticus to 65 gm. These basic data may be helpful in
understanding the mesh selectivity and fishery management of the Nile tilapia.