Fishway installation and fish habitat study for river ecosystem conservation in Indonesian streamsインドネシアにおける河川生態系保全のための魚道設置と魚類生息場の研究

Authors著者名

Siti Salmahシティ・サルマ1), Ahmad Junaidiアーマド・ジュナイディ, Izmiartiイズミアルティ, Masrizalマスリザル, Azharアザール

Affiliations著者所属

  1. 1) Dept. of Biology, Fac. of Mathmatics and Natural Science, Andalas University,
    Kampus Limau Manis, Padang Barat, Indonesia

Abstract要約

In order to obtain fundamental data for ecosystem conservation in Indonesian tropical streams, we carried out a field research, which includes fish and macro-benthos observation, physical habitat surveying and fishway installing, in a mountainous stream near Padang, West Sumatra, Indonesia, in 2001. As a result, we (1) collected 9 species of fish, 39 species of epilithic algae, and macro benthic 37 taxa, (2) found that most of the fish did not show any specific preference to water depth and velocity, (3) confirmed that almost all the fish used the fishway, and that the fishway was sufficiently solid against flooding, and (4) observed/collected many macro benthos including insects on the stones in the fishway, so that (5) it was suggested that even aqua-insect possibly used the fishway for their upstream- or downstream- migrating.


ウラカンダムへの魚道仮設の前後において、PHAB(ピーハブ)調査(魚類生息場の物理環境調査)を実施し、魚類およびベントス(藻類および水生昆虫)に関するデータ、およびそれらの生息場の物理特性、すなわち、水深、流速、底質(河床材料)、およびカバー(避難・隠れ場所提供物)に関するデータを得た。

設置した魚道はラリニア式魚道の改良型(待避所付き舟通し型魚道)である。魚道は、ダムとダム直下の減勢プールとをつなぐものと、減勢プールとその直下流河道とをつなぐものとのふたつを設置した。魚道勾配は1/10、流量は通常約0.09m3/s、魚道内の流速はもっとも速い部分で約1.4m/sであり、魚道の総延長は31.5mである。魚道底部の阻流材には木の板を用いた。また、折り返しプール内には、自然の渓流に似た流れをつくりだすために、こぶし大よりやや大きめの石を敷き並べた。

調査は2000年の11月から2001年の11月にかけて行われ、調査結果はPHABSIM(魚類生息場の物理環境解析)プログラム(IFIM:環境流量漸増評価法の一部)を用いて解析した。

調査水域には、魚類9種(アカラ、バダ、カペラス、クラリ、ムンクス、およびニラ)が生息していた。生息数は上流(1,479尾)のほうが下流(607尾)よりも多かった。PHABSIMによる解析の結果、これらの魚には水深、流速および底質に関して、特に偏った選好性はないことが解った。

藻類については、魚道設置前の調査では下流で33種、上流で34種が確認および採取された。優先種は、上・下流ともに Diatoma elongatum であった。魚道設置後には、下流で39種が確認され、優先種は Fragilaria copusina であった。

ベントスについては、昆虫類31種、貧毛類3種、ヒル類、線形動物類、蜘形類がそれぞれ1種ずつ確認され、密度は480.8~1,100.1ind/m2であった。動物性マクロベントスの構成は上・下流で異なっており、魚道はその構成に変化を及ぼすと考えられた。また、魚道内の石に付着した種数や密度は、自然の川より大きく、魚類のみならず水生昆虫もこの魚道を使って移動している可能性が示唆された。

水質は常に良好であった。

(推薦者:中村 俊六 訳)

Introduction

As Indonesia is developing, it's ecosystem, as a natural resource, seems to becoming endangered, as is true already in many developed countries. Loss of tropical stream fish is such a typical problem. In Indonesia, some tropical fish species seem to have already disappeared and many of them have become endangered, under the rapid progress of river development in modernization or channelization for flood control and water resources. For example, in West Sumatra, it is reported that the fish population of some species like garing, Labeobarbus spp., and kulari, Tylognathus hispidus, had been decreased drastically (Kottelat et al. 1993).

In order to obtain a powerful tool to design or think about how to conserve the healthy fish habitat or ecosystem in such Indonesian streams, we carried out 2 activities: (1) installation of a temporary fishway at a dam, and (2) PHAB-Study (study on physical habitat condition preferred by or suitable to fishes and macro benthos) at the downstream and upstream of the fishway before and after the fishway installation.

Study Site

The research was carried out between November 2000 and November 2001 at Sicincin (Lat. 00°34' South, 100°15' East), 2 × 11 Enam Lingkung sub district, Padang Pariaman district in the Batang Ulakan River, West Sumatra Indonesia (Fig 1). The catchment area of the site is around 60km2 and mainly consists of field forest and extensive jungle. The site is located about 42km far from city of Padang and the level of the site is around 40-60m upper from sea level. There are two seasons in this area, i.e. rainy season and dry season. The rainy season is normally from September to March and the dry season is from April to August. In dry season sometimes there is no water in some reaches in the river and in rainy season floods often attack the river.

Fig.1 Location of study site

Fig 1 Location of study site

Fishway Installation

We installed a temporary fishway on a dam (tentatively called "Ulakan Dam"; Fig 2) which is located in the mid reach of the Ulakan River, in May 16-June 12, 2001. The fishway, a kind of modified Larinier Pass, consists of 2 parts: (1) box-style fishway which is directly attached on the dam and (2) roof-attached fishway attached on the energy dissipation pool of the dam (Fig 3). The slope of fishway channel (0.4m width) is 1/10 and the total length is 31.5m.

Fig 2 Ulakan Dam

Fig 2 Ulakan Dam

Fig 3 Installed fishway

Fig 3 Installed fishway

Fig 4 Process of fishway installation

Fig 4 Process of fishway installation

Figure 4 shows the process of construction of the box-style fishway. We also installed many stones/cobbles inside the fishway, especially in the turning pools, after completed the fishway construction.

According to observation, a lot of fish ascended the fishway, then many fish which had crowded near the dam before the fishway installation were observed to be disappeared. We also confirmed the fishway to be sufficiently solid against flooding (Fig 5).

Fig 5 Installed fishway in a flooding

Fig 5 Installed fishway in a flooding

PHAB Study

We also carried out so-called PHAB-Study at the upstream and downstream of the dam before and after the fishway installation. The PHAB-study consists of 3 activities: (1) fish observation, (2) macro-benthos observation, and (3) measurement of physical habitat condition such as water depth, velocity, substratum and cover condition. The data obtained are analyzed by PHABSIM (Bovee, K. et al. 1997) then yield the HSC (habitat suitability criteria) for each species and life stage.

Fish micro-habitat study (fish observation and measurement of physical condition)

The PHAB-study was carried out 6 times (on Jan. 20, 21, Feb. 17, 18, Aug. 20 and Nov. 11 in 2001) at 2 sites (upstream site and downstream site; Fig 6 and 7), mainly focusing to fish habitat.

Fig 6 Upstream site (right) and downstream site

Fig 6 Upstream site (right) and downstream site

Fig 7 Upstream site (upper figure) and downstream site (lower figure)

Fig 7 Upstream site (upper figure) and downstream site (lower figure)

As a result, we collected the HSC data for 9 fish species, i.e., Akara (Pristolepis fasciata), Bada (Rasbora argyrotaenia), Garing (Labeobarbus soro), Kaperas (Puntius binotatus), Kulari (Thylognatus hispidus), Mungkus (Glossogobius biocellatus, Sicyopterus macrotetholepis, Sicyopterus micrurus) and Nila (Oreochromis niloticus)(Fig 8). Figure 9 shows some HSCs as of velocity.

Fig 8 Akara (upper left), Kaperas (upper center), Kulari (upper right) and Mungkus (lower left)

Fig 8 Akara (upper left), Kaperas (upper center), Kulari (upper right) and Mungkus (lower left)

Fig.9 Obtained HSC as of velocity for Mungkus (j: juvenile, a: adult) and Garing

Fig 9 Obtained HSC as of velocity for Mungkus (j: juvenile, a: adult) and Garing

As shown in the figure, these fishes prefer sometimes higher velocity (i.e. suitability index SI equal 1.0 at higher velocity) but sometimes does lower velocity, so that the generalized HSC indicates that these fishes do not show any specific preference as of velocity, even though there are some exceptions like as Garing adult. Almost similar tendency was shown in the HSC of depth and substratum. Thus, we may conclude that almost everywhere could be usable area for the tropical native fishes in such wild/natural streams, from the view point of (only) physical condition.

Benthic fauna study

The collection of data on water quality and samples of benthic fauna was also carried out at almost same time. The samples were collected at a set of pool and riffle. On August 20, the samples were collected also for the stones inside of the fishway under the guidance of Prof. K. Tanida, Osaka Prefecture University and the help of Mr. N. Jikei, Ms. course student of Toyohashi University of Technology (Fig. 10).

Fig 10 A group picture at a sampling of benthic fauna in the installed fishway (left corner: Prof. Tanida, right corner: Mr. Jikei)

Fig 10 A group picture at a sampling of benthic fauna in the installed fishway (left corner: Prof. Tanida, right corner: Mr. Jikei)

As a result, 33 taxa of epilithic algae were collected at the downstream site before installing fishway, including Bacillariophyceae (15 species), Chlorophyceae (13) and Cyanophyceae (5), and 34 species such as Bacillariophyceae (13 species), Chlorophyceae (16) and Cyanophyceae (5) at the upstream site. The taxa were dominated by Diatoma elongatum (Bacillariophyceae) at the both sites. After the installation of fishway, 39 and 18 species were collected at the downstream and upstream sites respectively and dominated by Fragilaria copusina (Bacillariophyceae).

Also the followings were found:

  1. 1. The macro-zoo benthic 37 taxa consisted of insecta 31 taxa, Oligochaeta 3 texa, Hirudinea, Nematoda and Arachnida 1 respectively.
  2. 2. The density ranges from 480.8 to 1,100.1 ind/m2.
  3. 3. The density and diversity of benthic animal were higher in the fishway than that in the natural stream bed near fishway.
  4. 4. Baetis spp. were most rapidly colonized on the (numbered and newly introduced) stones both in the fishway and in the natural bed, similar to the result for the introduced substrate in the Idaho's streams (Shaw, Minshall 1980) and for the artificial substrate in a Sumatra's stream (Izmiarti, Dahelmi 2000).

According to Prof. Tanida, it was suggested by the study the fishway was used by not only fish but also even aquatic insect. They used the fishway for their habitat and upstream- or downstream- migrating.

Acknowledgement

We are deeply indebted to: the all members of Ir_ECO and Andalas University's students for the great helps, Dean of Engineering Faculty of the Andalas University for the deep understanding to our activities, Prof. S. Nakamura, Prof. Kazumi Tanida and Mr. Yukio Ota for the useful suggestion, Mr. Jikei, Mr. Joe and Miss Yu-Feng for the special participation to the field research in Summer 2001, and PRO-Natura Fund for the financial support. Finally, maybe we must say thanks again to Joe and Prof. Nakamura for the devoted help in making this final report.

References

  • Kottelat, M. et al. 1993. Freshwater Fishes of Western Indonesia and Sulawesi. Periplus Editions Ltd.
  • Bovee, K. et al. 1997. Stream Habitat Analysis Using the Instream Flow Incremental Methodology, USGS Information and Technology Report 1997-0006.
  • Shaw, D.W. and G.W. Minshall. 1980. Colonization of an Introduced Substrate by Stream Macroinvertebrates, Oikos 34.
  • Izmiarti, Dahelmi. 2000. Macroinvertebrata dan Kolonisasinya di Sungai pada Kawasan Hutan Pendidikan dan Penelitian Biologi Universitas Andaras Padang. J. Biologica, 5.