of freshwater habitats in Singapore
Contrary to popular
belief, the freshwater habitat is not as homogeneous as it seems. There
are many types of freshwater, each with its own fauna. For convenience,
we have recognised several kinds here. It must be emphasised that many of
these habitat types gradually merge into each other, and the categorisation
used here is purely for convenience. It must also be noted that Singapore's
natural environment has altered considerably in the past 100 years, and
many areas have been lost to development.
Perhaps the most prominent and obvious to the majority of us are urban
habitats, i.e., drains and canals. These habitats are challenging
in the sense that there is almost no place to hide, the waters constantly
flowing, pollution may be rife, water sometimes very shallow, temperature
and pH fluctuations often extreme and predation serious owing to lack
of cover. Only the toughest fishes survive. Most are introduced. Typical
fauna include tilapia, guppies,
mollies and sometimes snakeheads. As increasingly
more streams become "upgraded" and "concretised", it must be anticipated
that such "immigrant" fishes will spread, always at the expense of
Reservoirs represent another common source of freshwater for Singaporeans.
They consist of two main types, namely the central catchment reservoirs,
surrounded by secondary forest, and the estuarine reservoirs which
are actually dammed up river mouths. The fauna here is more diverse,
but again, many species have been introduced. In the latter type,
certain species of euryhaline fishes are thus confined permanently
to freshwater. Fish ponds offer a similar habitat. The ubiquitous
tilapia is most abundant, as well as snakeheads, eels, labyrinth
fishes and some carps.
Of the natural flowing waters, three types may be discerned: open
country, secondary forest and primary forest streams. Open country
or rural streams are generally more common, but the fauna here is
often restricted to the tougher labyrinth fishes, catfish, snakeheads,
swamp eels, guppies and mollies. When such streams drain from catchment
areas, the diversity is greater, including barbs
and rasboras. The habitat in open country streams
is generally less predictable, with higher temperatures, greater silt
levels and increased risk of pollution. Many streams in the Lim Chu
Kang area are intermediate in character, having reasonable shade.
The waters, however, tend to have muddy bottoms, and organic pollution
as a result of chicken and duck wastes, discourages any great variety
of fish life.
The secondary forest streams abound in the catchment area. In the
less disturbed areas, more native fishes are present. The fauna here
includes barbs and rasboras as well as snakeheads, eels, etc. Interestingly,
many of these streams are free of introduced fishes like tilapia and
guppies. In the less disturbed areas in the centre of the catchment
area, acid water streams and swamps may be found. Singapore's rarest
fishes can be found here, most occurring nowhere else. In the least
disturbed areas, many of the habitats must have closely resembled
what much of Singapore was like a hundred years ago.
Stream in catchment area
Acid water swamp forest stream
Open country stream
The last category are the primary forest streams, and these occur only inside
Singapore's last patch of primary rainforest, mainly in Jungle Falls Valley.
The waters here, however, although pristine and clean, only shelter the
Forest Betta. In the drainages at the base of Bukit
Timah Hill, some natural ponds can be found. In these, rasboras, barbs and
snakeheads still abound.
The estuarine habitat is perhaps the most arduous for fishes which have
not overcome their osmoregulation problems. In this habitat, the tides,
outflow of freshwater (via drains) and amount of rainfall cause the salinity
levels to constantly fluctuate. The unpredictable salt water concentrations
encourage euryhaline fishes like scats, mollies and
gobies. Tilapias are also common in some areas. Mangrove
habitats present similar challenges. Both are considered together under
estuarine habitats. The substrate varies from rocky to muddy. Many of these
fishes will spend long periods in freshwater, but do better in slightly
salty (brackish) waters.
Fishes in Singapore
Amazing Fishy Facts
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