23 heavily vegetated with tickets of mangrove stands, and the indication of a closed
vegetation pattern surrounding the estuary. Interviews reveal that there are about 50 fishermen working within the estuary alone.
3.2 Methodology for mapping boundaries and land use change
In order to provide data on the current boundaries and land use patterns around the Butuah and Essei lagoons and estuary of the Whin river, these water bodies were mapped
using Trimble Juno ST Global Positioning System Receivers GPS. This information was complemented by data extracted from georeferenced google earth images. To
provide an indication of changes in the areal extent of the water bodies and also in the land use patterns within the immediate surroundings of the three water bodies, the current
boundary and land use data were processed and compared with boundary and land use data extracted from a 1973 1:50,000 topographic map of the area.
3.3 Measurement of hydrographic factors Water quality was assessed relative to predetermined standards for critical concentrations
for certain hydrographic factors and pollutants. The water samples were collected at different locations and depths namely surface and bottom from selected water bodies of
critical importance. Hydrographic parameters measured were:
- Salinity,
- Dissolved Oxygen DO
- pH,
- Conductivity,
- Temperature; and
- Turbidity
These were achieved with the help of Water quality checker Model: Horiba Water
Quality Checker U-10.
3.4 Plankton, benthic and littoral macroinvertebrate sampling
The phytoplankton and zooplankton were sampled with a 40 cm long plankton net net aperture 20 cm and mesh size 200 microns and fixed with 10 formalin. In the
24 laboratory,
the
phytoplankton and zooplankton
were examined under high power objectives of compound microscope and identified using plankton manuals Newell and Newell, 1963.
Three replicates of benthic and littoral samples were taken from five stations designated A
– E in each of the three water bodies for studies on the benthic and littoral fauna; where A was the station closest to the mouth of the water bodies, and E referring
to the upper limits of the northern section of the water bodies Figure 2. An Ekman grab 15 cm × 15 cm was used in collecting benthic sediments while littoral samples of soft
banks were collected by sweeping the sediments using a 50 cm × 50 cm quadrat with fixed net
800 μm. The random quadrat sampling method Krebs, 1999 was adopted at the mouth of the Whin Estuary Station A due to the rocky nature of the banks quadrat
size: 50 cm × 50 cm, and macrofauna occurring within the area enclosed by the thrown quadrat were collected. The sediment samples were screened in the field using a set of
sieves of mesh sizes 4000 μm, 2000 μm and 500 μm, and the animals retained in the
sieves were preserved in 10 formalin for detailed examination in the laboratory. Prior to sorting, a pinch of Bengal rose dye was added to the samples to stain the organisms and
enhance their visibility.
The macrofauna found were examined under a dissecting microscope and identified with the aid of laboratory manuals Edmunds, 1978; Dejoux
et al
., 1982; Yankson Kendall, 2001; Hauer Lamberti, 2006. Counts of the different taxonomic groups in the samples
were recorded separately for further analysis.
Figure 2:
Map of study area showing locations for benthic and littoral sampling A-E and collection
of water samples for water quality analysis A-G.
It is important to note here that, larger wetland areas exist beyond the study area. These existing wetland areas were not included in this study for lack of resources. Notice must
however be given that wetlands have been developed such as places west of Essei lagoon and behind the Effia Nkwanta Hospital. These would require further studies. For the
Whin river, larger tributary areas exist to the east and west exist that were not assessed in this present study, and across the main highway to the north. This also applies for the
north of the road at Butuah lagoon.
3.5 Fish sampling and measurements
