annexc - Newmont Mining Corporation

Annex C2 – Aquatic Resources Supplemental Information C2 - 1
FISH STUDIES DISCUSSION
Geomatrix (2008c) documented 34 fish species representing 14 different families during
seasonal sampling at 11 sites in the Study Area (Table 3-3). This compares with 23 species
from nine families of fish recorded from four sites during earlier work conducted in the
Study Area by SGS (2004c). Fish caught during the study represent about 50 percent of all
the species known to occur within the Pra River drainage basin (SGS 2004c). Considering
the limited portion of the Pra River watershed represented by the Study Area, this high
percentage is considered to indicate a diverse and healthy fish population is present. SGS
(2004c) reported fish production (i.e., catch per unit effort) in the Study Area was relatively
low and most of the fish were of small size classes. Based on studies by Geomatrix, this
does not appear to be an accurate representation of the fish populations in the rivers and
streams in the Study Area. It is more likely that the low fish catch by SGS was the result of
sampling methods used rather than changes in the actual abundance and diversity of fish
populations in the Study Area.
During the SGS study, the highest fish production in the watershed occurred in the Mamang
River at Kotokuom, during the wet season. During the wet season sampling conducted by
Geomatrix, the highest catches were made in the upper Pra near Abodum and in the Afosu
and Abesu Streams that are tributary to the Mamang River. The efficiency of sampling gear
is limited during the high flows in the main stem reaches of the Pra and Mamang Rivers. As a
result wet season data are not necessarily representative of the true diversity of populations
present in these areas. In the dry season, the highest and most diverse fish populations were
found in the main stem Pra and Mamang Rivers. This is the expected result as fish
populations are concentrated in the main channels of these rivers as flows recede during the
dry season.
The single most diverse and highest catch, in numbers of fish came from the Pra River, west
of Ntronang, at station SW22 where approximately 1,600 fish represented by 15 species
from eight different families were identified. Two other stations yielded approximately 1,000
fish in the Geomatrix study during the dry season sampling. These were completed at the
Mamang River stations at Mamanso and near Nkwanten with 14 and 12 species recorded,
respectively. The lower Pra River stations near Kotokuom and Ofoase Praso also had good
species diversity with 11 and 12 species identified, respectively.
Two families of fish dominated all catches numerically; the minnows and carps family
(Cyprinidae) and the African tetras and tiger fishes (Alestidae). The minnows from the
genus Barbus were captured at every sample station during the Geomatrix aquatic studies
(Geomatrix 2008c). Barbus trispilos and B. puncititaeniatus were the most common and often
dominated the catches in numbers. B. trispilos was present at every station sampled by
Geomatrix both main stem rivers and tributary streams. This is in contrast to the results of
the SGS (2004c) study that concluded that Barbus spp. “need to be protected because of
their restricted habitat requirements.” The other two most common and widespread
species are African tetras from the Alestidae family; Brycinus leuciscus and Micralestes
occidentalis.
Akyem Gold Mining Project November 2008 FINAL EIS