Diversity and distribution of fish fauna of upstream and downstream areas at Koto Panjang Reservoir, Riau Province, Indonesia

Introduction

The capture fishery and aquaculture sectors play an important role in the Indonesian economy through increased income, diversification of livelihoods, supply of animal protein, and foreign exchange earnings. In 2018, the total fishery production of Indonesia was 23.186,442 metric tons, of which 467,821 metric tons was obtained from inland capture fisheries, 6,603,631 metric tons was obtained from marine fisheries, and 16,114,991 metric tons was obtained from aquaculture fisheries production¹. A total of 1,300 fish, including 40 endemic species are known to inhabit in the freshwaters of Indonesia, with 16 exotic species recorded in Indonesia². The production from the inland capture fisheries of Indonesia comes from wetlands (rivers, lakes, swamps, oxbow lakes, floodplains, etc). In Riau Province, one of the rivers that produce freshwater fish from capture fishery is the Kampar Kanan river. Fithra and Siregar³ found 54 species in Kampar Kanan River, while Aryani⁴ reported 40 species. At present, major Cyprinidae species such as Leptobarbus hoevenii, Osteochilus haselti and Rasbora argyrotaenia, along with exotic species, such as common carp (Cyprinus carpio) and Nile tilapia (Oreochromis niloticus), are the available species of fish at local food markets.

According to Mulyadi⁵, Kampar Kanan river is one of the largest rivers in Riau Province. It is approximately 213.5 km long and between 125 to 143 m wide, with significant capture fishery potential. Since 1996, this river has been dammed into a reservoir (Koto Panjang Reservoir) for the operation of a 114 MW hydroelectric power plant. The dam height is 96 m and located at altitude of 85 m above sea level⁵, and at the geographical position 0°17'23.76˝N and 100°52'53.39˝E. However, at the location of the dam, there is no fishway. The abiotic and biotic characteristics of river ecosystems can be affected by the construction of dams. These conditions have an impact on mortality and failure of fish migration^6–9. The hydrologic regime of streams changing from lotic to lentic can influence the water retention in the reservoir. In general, the lentic condition causes a decrease in native species and then an increase in exotic species^10,11. Furthermore, the degradation of aquatic fauna habitats can be caused by an increase in homogeneity of water channels, which has an effect on the seasonal flow variability of river¹². The reduction in river runoff also affects the habitat and distribution of fish fauna.

On the other hand, there are serious threats to the original fish biodiversity in the downstream and upstream regions of the reservoir due to the dam of the hydroelectric power plant, such as sand mining in river, land use change and aquaculture activity with cages, which can affect the depth of river water, food availability, and breeding sites. Amadi et al.¹³ state that original biodiversity can be eroded by habitat degradation and alien species impact. Meanwhile, aquaculture heavily impacts the structure and diversity of local fish communities^14,15. Hence, it was essential to study fish diversity continuously in different ecosystem areas, including upstream and downstream areas at Koto Panjang Reservoir, Riau Province, Indonesia.

Methods

Results

Icthyodiversity in the upstream and downstream areas at Koto Panjang Reservoir

A total of 44 species belonging to 19 families and 33 genera were sampled from the four sites over one year in the upstream and downstream areas at Koto Panjang Reservoir. There were seventeen species which are commercially important, as determined by their high market value. These species including ornamental fish species such as Chromobotia macrachantus, Chromobotia hymenophysa, Thrichogaster trichopterus and Mystus micracanthus. The highest ichthyodiversity in study area was calculated during July and August 2018 (44 species), followed by June and September (42 species), May and October (41 species), April and November (39 species), December (38 species), March (36 species), February (30 species) and January (26 species). Numerically, the most abundant and diverse family was Cyprinidae, comprising of 16 species, followed by Bagridae and Channidae (represented by four species each). The fourth most diverse family was Gobitidae, represented by three species in the study area. The least diverse families were Claridae, Pangasidae, Anabantidae, Mastacembelidae, Osphronemidae, Pristolepididae, Cygnolossidae, Notopteridae, Hemiramphidae and Cichlidae, represented by only one species for each (Table 2). Barbodes schwanifeldi, Hemibagrus nemerus, Ompok hypophthalmus, Rasbora argyrotaenia and Oreochromis niloticus were recorded as the most abundant species, comprising 5.88%, 6.20%, 6.71%, 8.76% and 9.80% of all fish caught, respectively. The least abundant were Channa pleurothalmus, Hemibagrus wyckii and Pangasius pangasius, representing 0.06%, 0.08% and 0.09%, respectively.

Table 3 shows different diversity indices used to calculate the species abundance data. The highest species richness was recorded between the months of June and September. Similarly, the highest values for Shannon’s diversity index (H’) were achieved during October 2018 (2.27), August and November 2018 (2.23), and the lowest values during January and February 2018 (1.74 and 1.91).

Table 3. Monthly diversity indices of fish fauna in the upstream and downstream areas at Koto Panjang Reservoir.

Index	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Total
No. of individuals	437	484	534	635	670	754	848	873	854	772	641	515	8017
Richness (S)	26	30	36	39	41	43	44	44	42	41	39	37	44
Simpson (1/D)	0.25	0.22	0.22	0.23	0.22	0.22	0.20	0.19	0.19	0.18	0.18	0.20	0.21
Shannon’s (H’)	1.74	1.91	2.14	2.00	2.07	2.06	2.16	2.23	2.21	2.27	2.23	2.17	2.10
Evenness (e ˆH/S)	0.22	0.22	0.24	0.19	0.19	0.18	0.19	0.21	0.21	0.24	0.23	0.24	0.19

The highest Simpson diversity index (I/D) was recorded during the months of January (0.25), followed by April (0.23), February, March and May (0.22), and the lowest value was recorded in the months of October and November (0.18). Similarly, the highest values of species evenness (H/S) was recorded in the month of March > December and its least value was recorded during the month of June. Furthermore, the detailed values of different diversity indices on the basis of sampling sites were given in the Table 4. Whereas, the Sorenson’s coefficient (CC) between upstream and downstream areas at Koto Panjang Reservoir were presented in Table 5. The commercially important fish species captured in downstream Reservoir were Hemibagrus wyckii, Hemibagrus nemurus, Wallago leerii, Pangasius pangasius, Osphronemus gourami, Puntioplites bulu, Rasbora argyrotaenia, Channa striata, and Channa micropeltes. Whereas, in the upstream Reservoir found were Pristilepis grooti, Oxyeleotris marrmorata, Hemibagrus nemurus and Channa striata and Oreocromis niloticus.

Table 4. Site based diversity indices of study area in the upstream and downstream areas at Koto Panjang Reservoir.

Index	KM	BB	RB	KK	Total
No. of individuals	1701	1370	2135	2811	8017
Richness (S)	18	21	37	35	44
Simpson (1/D)	0.31	0.18	0.22	0.20	0.21
Shanon,s (H’)	1.51	1.95	2.00	2.03	2.10
Eveness_ e ˆH/S	0.25	0.33	0.20	0.22	0.19

Note: KM = Koto Mesjid, BB = Batu Bersurat, RB = Rantau Berangin, KK = Kuok.

Table 5. Sorenson’s coefficient (CC) between sites in the upstream and downstream areas of Koto Panjang Reservoir.

Site	KM	BB	RB	KK
KM
BB	0.92
RB	0.65	0.54
KK	0.57	0.56	0.80

Note: KM = Koto Mesjid, BB = Batu Bersurat, RB = Rantau Berangin, KK = Kuok.

The abundance and number of families found between sites was varied. At KM and BB (upstream reservoir), 8 and 11 families were found, respectively, while at RB and KK (downstream reservoir), 16 and 15 families were found, respectively (Figure 1). The dominant families in each site was Cyprinidae, comprising 33.45%, 50.95%, 43.04% and 39.35% of all fish caught at KM, BB, RB and KK, respectively. Whereas, the exotic species, especially Nile tilapia (O. niloticus), in each site comprised 14.11%, 20.15%, 5.62% and 5.34% of all fish caught at KM, BB, RB and KK, respectively. Some differences were also noted between the upstream and downstream reservoirs areas (Figure 2), with a slight increase of exotic species in the upstream reservoir (from 11.39% to 34.66%) and a corresponding decrease of native species (from 88.61% to 65.34%).

Figure 1. Abundance and composition of aquatic fauna in the upstream and downstream reservoir.

a) Koto Mesjid, b) Batu Bersurat, c) Rantau Berangin and d) Kuok.

Figure 2. Percentage of individuals of native and exotic fish species in upstream (Koto Mesjid, KM, and Batu Bersurat, BB) and downstream reservoirs areas (Rantau Berangin, RB, and Kuok, KK).

Discussion

Our results showed that the highest abundance and diversity of fish species collected in June, July and August, which may be due to a lesser water current in the study area during these dry season months. According to Kriaučiūnienė et al.²² the abundance of fish species in rivers can be affected by river discharge. However, future alterations in river water temperature will have a significantly larger influence on the abundance of fish than river discharge. Overexploitation and illegal sand mining have affected the abundance of fish in the Kampar Kanan river²³. Furthermore, the fundamental measures of aquatic ecosystems, including species richness and diversity indices, are influenced by the alterations in abiotic factors such as river water temperature and discharge^24–27.

Our study also revealed significantly lower species diversity in KM and BB (upstream reservoir) compared to that of RB and KK (downstream reservoir). The overall richness in KM was much lower than that found in RB (18 vs. 37). During the research period, we also recorded a slight increase in exotic species in the upstream reservoir and a decrease in native species. Therefore, the implication of exotic species such as Nile tilapia and common carp have negative effect to native species in the upstream area of Koto Panjang Reservoir. In contrast, in a Portuguese reservoir, it was found that there was a slight increase in exotic species in the downstream reservoir⁶. This result might be a consequence of cumulative impacts of cultivation of fish in floating net cages, such as Nile tilapia and common carp. According to Russel et al.²⁸, Nile tilapia cause the extinction of native fish species by preying on eggs, fry and small fish of other species. On the other hand, the decrease in species richness can be influenced by aquaculture activity, such as water quality degradation, intensified competition, invasive species, and habitat fragmentation^14,29–31. Koto Panjang Reservoir was categorized as eutrophic, with level index values ranging from 4.6-5.2³². According to Edwards³³, species with high environmental tolerance would be survive in poor environmental conditions, such as high pollution caused by food waste at the reservoir, while the sensitive species will disappear. Furthermore, fish populations in a reservoir can be affected by hydropower dams^5,6. In addition, the intensifying competition for food and space between wild species and the large number of cultured species will lead to a decrease in wild fish numbers^34,35.

Our study confirmed the existence of three species, Pangasius pangasius, Wallago leerii and Chitala hypselonotus, at Koto Panjang Reservoir that were not found previously by Warsa et al.³⁶ and Krismono et al.³⁷. The study area also represents the area of the Kampar Kanan river with the largest fish species, including W. leerii, H. wyckii and P. pangasius. The construction of the dam for power generation purposes is posing serious threats to the biodiversity of Kampar Kanan river. After the construction of the Koto Panjang dam on Kampar Kanan river, the movement of fish upstream has been restricted. Osteochilus kelabau has not been reported at RB in our study although this species has previously been found in this area⁴. Similarly, the population of H. wyckii has also been dramatically reduced and restricted between Koto Panjang Reservoir barrages and Kampar Kanan river after the construction of these barrages. H. wyckii in the Kampar Kanan river is categorized as ‘vulnerable to endangered’³⁸. According to Piria et al.³⁹, the disturbances to the fish assemblage pattern have coincided with the presence of multiple stressors of human origin, such as pollution, flood protection and dam construction. Meanwhile, dams can of change the hydrological dynamics, patterns of biological production, loss of native species in the downstream regions and distribution of organisms in space and time^5,7,12,40,41.

There are a number of inadvertently introduced fish species in the upstream and downstream Reservoir, such as O. niloticus, Cyprinus carpio, Leptobarbus hoevenii and Pangasianodan hypophthalmus, while rest of the 40 species belong to the native fish fauna of the Kampar Kanan river⁴. The unique feature of the abundance data was that the exotic family Cichlidae is well established and its population is increasing day by day, especially in the upstream areas at Koto Panjang Reservoir. In recent years, the Koto Panjang Reservoir has had very important roles, such as housing power plants with a capacity of 114 MW and serving as a fishery capture and aquaculture area with floating net cage farming, especially for the cultivation of O. niloticus. Cichlidae was the third most abundant family. These alien fish species represent a significant risk for the local fish community and other aquatic animals. Gu et al.³¹ state that the invasion of O. niloticus negatively affected the fishery economy and native fish species in the Pearl River of Guangdong Province, China.

In addition to the species richness (S) analysis, Shannon diversity index (H’), Simpson diversity index (D) and evenness (H/S), we also analyzed the Sorenson’s coefficient (CC) between the upstream and downstream sites. The Sorenson’s coefficient for each site varied between 0.54 and 0.92. The highest value of Sorenson’s coefficient was recorded between KM and RB, at 0.92, and the lowest value was recorded between BB and RB, at 0.54 (Table 5). According to Sorenson’s coefficient, these communities have quite a bit of overlap or similarity.

The high diversity of native species in the water body will decrease their tolerance in poor aquatic environments. In contrast, the invasive fish species have a high tolerance to poor water quality⁴². The interaction between different species, combined with the limnological and physical properties of the aquatic ecosystem, may influence the diversity and distribution of fish fauna⁴³. In this study, the diversity of fish to be found smaller than Fhitra and Siregar³, who reported 58 fish species belonging to 23 families and 40 genera from Kampar Kanan river. Simanjuntak et al.⁴⁴ described 86 species and 21 families in the Kampar Kiri river of the Kampar District. On the other hand, Nurdawati et al.⁴⁵ reported 96 species in the Batanghari river, Indonesia. Additionally, Bahri⁴⁶ described 86 species in the Musi river and Kottelat and Whitten⁴⁷ reported 1300 species of freshwater fish across Indonesia that live in wetlands (rivers, lakes, bogs, oxbow lakes, floodplains, etc.).

Conclusion

The results indicate that the diversity and distribution of fish fauna in upstream and downstream areas of the Koto Panjang Reservoir were varied, and the evenness was low. The abundance and composition of fish in each site was dominated by Cyprinidae families, although exotic species were more dominant in the upstream reservoir compared to the downstream reservoir areas. Therefore, the management of the river and reservoir in a more holistic manner is important, for example, the management of land use, sand mining and aquaculture activity, as well as possible habitat restorations. All the factors above are a prerequisite for the environmental sustainability and conservation of fish diversity in the upstream and downstream areas at Koto Panjang reservoir and other regions.

Data availability