Abstract:
Natural wetlands of Gilgel Gibe watershed in the southwestern Ethiopia have various
socioeconomic and ecological values such as habitat for a variety of plant and animal species,
and water source for human and livestock consumption. Although these values and services are
appreciated, wetlands in the catchment are subject to increasing anthropogenic disturbances.
The objective of this study was to determine the effects of these anthropogenic disturbances on
water and habitat quality, fish and macroinvertebrate assemblages. A cross-sectional study was
carried out from March to April 2014 in three wetlands located in Gilgel Gibe watershed. A total
of 23 sites were sampled. Canonical Correspondence Analysis (CCA) and multiple linear
regression models were used to identify influencing variables on macroinvertebrate and fish
communities. A total of 4,349 macroinvertebrate individuals belonging to 11 orders and 33
families were collected. The most abundant orders were Hemiptera 2478(57%), Coleoptera
557(13%), Diptera 438(10%), Odonata 389(9%) and Ephemeroptera 361(8%) represented by 24
families. 760 different fish specimens were collected. Oreochromis niloticus was the dominant
species which accounts 77.5 % followed by Labeo forskalii (18.16 %), Garra dambeensis (3.42),
Garra chebera (0.79%) and Labeobarbus intermedius (0.13 %). CCA analysis clearly indicated
that environmental factors such as concentration of DO, TSS, ammonium, chloride, turbidity,
water temperature, secchi depth, conductivity, water depth, sludge depth and pH influence the
structure of wetland fish and macroinvertebrate communities. Furthermore, Macroinvertebrate
descriptor was best predicted (R2 = 0.55) by water depth and sludge depth whereas fish
descriptor was best predicted (R2 = 0.53) by sludge depth, ammonium and TSS. These variables
provided clear interpretations of water quality and habitat deterioration of natural wetlands in
the Gilgel Gibe watershed due to human impacts from catchment land use. Therefore, creation of
awareness for proper utilization of natural wetlands and their related ecosystem services in the
Gilgel Gibe watershed, where wetland resources are being lost at a high rate, and continue to be
at high risk due to expansion of agricultural and other development activities. The finding of this
study can complement the previous studies on wetlands and surrounding watersheds to prepare
a complete monitoring tools and metrics which can give results to make informed decisions for
management and restoration of wetland ecosystem.
