Environmental Assessment
Volume B-4.3
Mine
Fish and Aquatic Resources
Ambatovy Project
245
January 2006
habitat type resulting from high variation in instream cover (QESF112) and
channel size. QESF125, located on Sahaviara River and QESF115, on the
Mangoro River were the only large river sites sampled. No significant temporal
difference in species associations was observed between high flows and low
flows, indicating possibly little seasonal movement or migration, at least within
the smaller streams which predominated in the study area.
Generally, the endemic fish species dominated in undisturbed habitats, occurring
at >60% of sampling sites. In contrast, introduced species, such as the
anabantid
,
Ctenopoma
ansorgii
, and the
poecelid
,
Xiphophorus maculatus
, were
more prevalent in disturbed areas. In addition to habitat degradation due to
deforestation, endemic species are threatened by competition from introduced
species, in particular from
Xiphophorus
maculatus
. Also of concern was the
presence of
Channa maculata
(blotched snakehead), encountered only in the two
large river sites sampled in the Mangoro drainage. This fish is an introduced
voracious predator, which has had major impacts on native fish populations in
Madagascar (Sparks and Stiassny 2003).
All fish encountered in the streams are relatively small-bodied species, and are
not highly used for food fish. However, the wetlands areas or larger downstream
water bodies may contain fish populations of importance (i.e., exotics such as
Tilapia
sp.) for artisanal fisheries.
Aquatic Macro-Invertebrates
A total of 70 macro-invertebrate taxa were recorded in the mine LSA during the
2004-2005 survey. All taxa recorded in 1998 were confirmed during the 2004-
2005 survey (Table 4.3-3). In contrast to the fish fauna, both diversity and
abundances of the macro-invertebrate fauna were high. However, similar to fish
fauna, aquatic macro-invertebrate diversity and abundance were generally higher
at undisturbed primary forest sites than deforested locations; the highest species
richness (51) was recorded at site QESF110 in an undisturbed primary forest.
The ephemeral ponds were fishless but contained a unique assemblage and
diversity of macro-invertebrates and plankton.
Endemic and Native Species
Fish
The fish fauna within the mine LSA contains four endemic fish (
Rheoclès
alaotrensis
,
Ratsirakia
legendrei
, one suspected new undescribed
Ratsirakia
species and the suspected
Rheoclès
“Ambatovy” species) These fish belong to
one of the two freshwater fish families endemic to Madagascar, the
Bedotiidae
or
Malagasy Rainbowfishes, with two genera (
Bedotia
and
Rheoclès
).
