BENTHIC FAUNA OF ROSETTA NILE BRANCH (EGYPT)

BENTHIC FAUNA OF ROSETTA NILE BRANCH (EGYPT)
BY
A.A. SAMAAN*; S. M. ABUOL EZZ;
S. A. SALEM AND A. M. SOLIMAN
*National Institute of Oceanography and Fisheries,

Key words: Benthic fauna, Rosetta Nile Branch.

ABSTRACT
The benthic fauna of Rosetta Nile Branch (Egypt) was estimated
seasonally for two successive years between May, 1987 and February,
1989. The community consisted ofmembers ofthe phyla Annelida (l0
species), Arthropoda (8 species) and Mollusca (7 species). Theirannual
averages amounted to 2,657 org/m2 during the first year increased to
4,225 org/m2 in the second one. The total biomass ofbenthos was high
whenever molluscs appeared in abundance due to their big size. Their
annual averages were 104.8 and 70.95 g, fresh wt/m2 for the two
successive years respectively. The most dominant species comprised
Chaetogaster limnaei and Chironomus larvae. Besides, other species
appeared frequently such as Branchiura sowerbyi, Tubifex tubifex, Nais
sp. and Bellamya unicolor. Most ofthe recorded species are muddy
bottom dwellers which can tolerate low oxygen content and are
widespread in inland waters ofEgypt and Nile System.
The benthic fauna showed marked variations in species composition
and distribution between the different Nile localities. The highest
annual averages were recorded at the littoral infront ofKafr EI-Zyat
City during the first year (average 8517 org/m2) mainly due to
Chironomus larvae and at the mid-stream site near to EI-Khairya
Barrage in the second year (average 9, 779 org/m2) as produced by
Chaetogaster limnaei. They showed also wide fluctuations from one
~eason to .the other, but the higher values were usually observed in
summer and autumn.