bin

#11231 Don Cat stream, Phong Thai district, Vietnam

Sponsored by

Viet Nam, Thừa Thiên Huế, Phong Thai District

Don Cat is a unique stream formed by underground springs emerging through coastal sand dunes, creating a distinctive freshwater ecosystem in central Vietnam.

During the dry season, water levels decrease and the stream becomes shallow with a gentle current. In the rainy season, increased flow removes algae growing on rocks and submerged branches, resulting in clearer water as algae have limited time to establish.

The stream is located in Phong Thai District, Thua Thien Hue Province, Vietnam. It supports a variety of native freshwater fish, but the species that attracted my attention most is the Vietnamese Cardinal Minnow (Tanichthys micagemmae). Its shimmering golden body, bold black lateral stripe, and bright red fins make it a remarkable small schooling fish.

My interest in this species inspired me to learn more about its natural habitat. The more I researched, the more fascinated I became by the ecosystem of Don Cat, ultimately leading me to choose this location as a biotope reference.

Submitted by
Nguyễn Quốc Điền Lương
GPS
16.5466137, 107.4535828
Geographical region
Southeastern Asia
Drainage Basin
South China Sea
River catchment
Central Vietnam coastal plain
Water body type
Stream
Water body name
Don Cat
Water body part
Water body course
Water body: tributary of
Tributary name

Videos above and below water


Warning: Undefined variable $fish_parent in /home/biotopea/public_html/wp-content/themes/bap/content-bin.php on line 55

Water Chemistry

Water information

Water type
Freshwater
Water color
Black water
Water transparency
Medium
Concentration of sediments
Low
Water temperature
28 °C
Water flow/curent
Slow

Chemical parameters

pH
6.8
Conductivity
574
GH
37.5 mg/l
dGH
KH
dKH
Dissolved Oxygen
70 %

Substrate in nature

Sand
White
Pebble/Gravel
None
Stone
None
Stone form
Silt/Mud
None
Leaves
Many
Driftwood
Many
Submerged terrestrial vegetation
Yes

Aquatic Biotope

Date of collecting
8 November, 2025
Collecting area
Backwaters
Water depth
0,2m
Air temperature
28 °C
Sunlight
Partial shade

Environment

Environment
Untouched
Surrounding area

The stream is a narrow freshwater channel flowing through a sandy landscape. The water is shallow, slow-flowing, and clear, with a light amber tint caused by dissolved tannins from decomposing leaf litter.

The substrate consists mainly of white sand covered by a scattered layer of fallen leaves. Riparian vegetation, including shrubs, ferns, and small trees, provides partial canopy cover, creating a shaded environment with limited submerged aquatic vegetation.

Organic debris such as leaves and small branches provides shelter and feeding areas for native fishes and aquatic invertebrates.

Underwater landscape

The streambed is composed primarily of white sand covered by a dense layer of decomposing leaf litter. Fallen branches, woody debris, and submerged roots create a complex three-dimensional structure that provides shelter for small fishes and aquatic invertebrates.

The water is clear, with a light amber coloration caused by dissolved tannins released from decaying leaves. Submerged aquatic vegetation is virtually absent, while riparian vegetation provides a continuous input of organic matter.

Small schooling fishes occupy the mid-water column, whereas leaf litter and woody debris serve as important feeding and refuge habitats.

Fishes:

  • Tanichthys micagemmae (Cyprinidae) – Vietnamese Cardinal Minnow – 200
  • Oryzias pectoralis (Adrianichthyidae) – Pectoral Ricefish – 50
  • Trichopsis vittata (Osphronemidae) – Croaking Gourami – 9
  • Trichopodus trichopterus (Osphronemidae) – Three Spot Gourami – 7
  • Yunnanilus cruciatus (Gastromyzontidae) – Cruciatus Loach – 50
Threats to ecology

The stream is naturally influenced by seasonal flooding during the monsoon period, which reshapes the sandy substrate, redistributes woody debris and leaf litter, and alters channel morphology.

Additional threats include prolonged dry periods, degradation of riparian vegetation, and potential impacts from climate change. Despite these pressures, the habitat still retains many of its natural structural features, including intact riparian vegetation, abundant leaf litter, and submerged woody debris that support native aquatic biodiversity.

Riparian zone

Trees near the aquatic habitat
Many - Melaleuca cajuputi (Myrtaceae)