Abstract
My PhD thesis presents a comprehensive investigation into the impacts of the Perjaya Dam on the fisheries of the Komering River, encompassing both ecological studies and social surveys. I combined ecological data from over a 30-year period and carried out additional field surveys to assess the ecological changes in the river caused by the construction of the dam. In addition, I explored the local communities’ perceptions of the effect of the dam on their livelihoods and fishery resources. The main findings of the thesis shed light on the significant challenges posed by the dam on the fisheries sector, its social implications, and the shortcomings of fishway facilities implemented to mitigate these impacts.
While the global construction of dams and weirs has increased food production, energy sufficiency and water security, it has significantly reduced river health, fish populations and fish diversity. The impacts on fish and their habitats are leading to decreased biodiversity, reduced fish catches and smaller incomes of local fishers and these are all significantly impacting livelihoods. The Indonesian government has invested heavily in developing water infrastructure and so far, thousands of dams and weirs have been built to irrigate agriculture and generate hydropower. But the proliferation of this infrastructure is becoming increasingly associated with declining river health, negative biodiversity outcomes and human impacts.
Globally, technical solutions, such as fishways, are often constructed to mitigate the impacts of dams and weirs. These have varying degrees of success depending upon the design principles, target species and level of investment into mitigative technology. Across Indonesia, presently, there are only two infrastructures that have been equipped with fishways as an engineering solution to connect fish migration pathways. One of these sites, the Perjaya Dam, which is equipped with a pool and weir fishway, was selected in this study to examine whether the dam has an impact on fish populations and whether the existing fishway is adequate.
The work in this thesis sought to link together the ecological, people and engineering aspects of dam and weir construction to build a multi-disciplinary understanding of the impacts on fish. It sought to bridge several key knowledge gaps needed to “mainstream” the consideration of fish in river infrastructure planning and assessment.
Although many dams and weirs have been constructed in Indonesia, their potential impact on fish populations has not been studied. My research sought to understand if dams and weirs impact fish populations and the livelihoods of local communities. In addition, I examined the effectiveness of the existing fishway at the Perjaya Dam to understand whether fishway performance is sufficient to facilitate fish movement and also assess whether fishing activities within the fishway reduce passage success.
I took a mixed methods approach, combining ecological and social data to gain a holistic overview of the impacts of the Perjaya Dam. My methods took three forms as follows:
(a) Ecological impacts of the Perjaya Dam:
The first line of inquiry was to build the evidence base that dams and weirs can impact fish ecology. I hypothesized that, 30 years following construction of the Perjaya Dam, which included a fishway, that there should be few differences in fish community structure, upstream and downstream, if the fishway was working adequately. I used standardized experimental fishing methods to examine the fish community differences upstream and downstream of the Perjaya Dam to determine if there were significant differences in fish community structure that may be attributed to the presence of the dam. I surveyed fish community at multiple sites, using three different fishing gears (gillnets, castnets, and bait traps) upstream and downstream of the Perjaya Dam in the Komering River. Sampling locations were at 0 km, 1 km, 5 km, 10 km, and 20 km from the dam, both upstream and downstream. Spacing the sampling sites at this distance aimed to make sure the reservoir effect did not bias data collection.
(b) Social understanding of importance of fish and perceptions of the dam:
The second line of inquiry was to understand the dependence of local fishers and households on inland fisheries. It has long been suggested that Indonesian households have a strong dependency on fisheries, but this has not been empirically demonstrated. Working with communities in the Martapura district, South Sumatera, I interviewed a range of “key informants” from a range of difference industries to understand the importance of the fishery and whether locals perceived that the dam has facilitated any changes to the Komering River. Data collection was divided into a two-stage process starting with interviewing key informants using semi-structured interviews, followed by a questionnaire survey with fisher household respondents. The key informant interviews aimed to elicit key themes and understanding of the local, national, and regional contexts and the importance of fisheries in the Komering River region. The findings from the key informant interview data aided in the development of the questionnaire survey and to understand the importance of fisheries to local people and perceptions of local people of the changes in the river and fisheries since the Perjaya Dam construction.
(c) Ecological survey of a technical solution (fishway) to attempt to mitigate the dam effects:
The third line of inquiry was an ecological investigation into the effectiveness of the Perjaya Dam fishway. The combined impacts of the fishway design and fishing pressure in the fishway may be having a significant impact on fishway success, and subsequently on fish biodiversity upstream of the dam. Here I aimed to determine if the pool and weir fishway at the Perjaya Dam was working effectively in facilitating upstream fish movements. I hypothesised that the implementation of a Japanese fishway design, combined with intensive capture fisheries, would lead to sub-optimal passage success at the site. Fishway trapping in the bottom and top of the fishway was performed in the presence and absence of fishers was conducted to evaluate fishway success. The results will provide valuable insights into whether the design of the fishway and/or fishing pressure significantly impacts the success of fishways.
The ecological studies conducted in the Komering River revealed a strong decline in fish populations and a loss of species diversity following the construction of the Perjaya Dam. This indicates a direct and long-lasting impact on the river’s aquatic ecosystem. The dam’s presence obstructed fish migration routes despite the presence of a fishway. Key results included that 13 of 36 species were found only downstream of the dam and five of 36 species were found only above the dam. There were significant differences fish community composition between upstream and downstream regions using either fish abundance, species richness or species diversity as the response variable.
The key informant interviews and questionnaire found people reported fisheries played a crucial role in the local economy, with fish being a primary source of income for households in the region. Furthermore, fish were found to be the primary source of protein in the diet of the local communities. The decline in fish populations caused by the dam’s construction was perceived to have had severe socio-economic consequences for these communities, affecting their food security and livelihoods. The social surveys conducted among local fishers and communities revealed a consensus that the Perjaya Dam had contributed to the losses in the fishery. The negative perceptions were echoed by local stakeholders who called for improved legislation and better compliance measures to address the issues faced by the fishery. The need for effective policies to restore and sustainably manage the fishery resources was evident.
Key findings included that fishing activities are vitally important for generating income, consumption, and fish are the main source of protein for the respondents, particular for the poor who rely on fish for their crucial income and food sources. They often consume small fishes whole, this is a rich source of calcium and other essential elements. The presence of the Perjaya Dam was perceived by respondents to negatively impact fish populations and their habitats. Therefore, any planned dams should be carefully considered even with a fishway because I found a strong evidence of fish community fragmentation between upstream and downstream the Perjaya Dam. In addition, the respondents believed that there is lack of involvement of fisheries sector in water infrastructure development planning and management that leads to natural resources degradation.
One attempt to mitigate the dam’s impact was the implementation of a fishway, designed to facilitate fish migration and maintain the ecological connectivity. However, a carefully controlled fishway trapping study revealed that the fishway was not successful in fulfilling its intended purpose. One of the primary reasons for its failure was that it was designed for Japanese fish species, which differed from the indigenous Indonesian fish species in the Komering River. There were various other principles of best practice fishway design including understanding of local hydrology and hydraulics which had been omitted by the designers. Additionally, local fishers actively exploited the fishway as a fishing ground, further reducing fish populations and compromising the fishway’s functionality.
My results found that the Perjaya Dam fishway is successfully passing 27 species and a diverse range of size classes. However, eleven species were not able to ascend the full length of the fishway. Collectively, our results suggest some modifications to future fishway designs are needed for Indonesian fishways to improve fishway efficiency for fish species that are threatened by dams.
The outcomes of this research highlight the urgent need for comprehensive measures to address the ecological and social challenges posed by the Perjaya Dam on the fisheries of the Komering River. I emphasize the importance of integrating ecological research with socio-economic studies to devise effective strategies for sustainable fisheries management. Furthermore, the study highlights the significance of considering local contexts and indigenous species when implementing interventions like fishways. My findings provide valuable insights for related stakeholders such as policymakers, environmental agencies, and local communities to collaboratively develop and implement appropriate conservation and management measures to restore and protect the fisheries of the Komering River, and rivers in Indonesia more broadly. It is my hope that this research contributes to the ongoing dialogue on sustainable river management and helps steer Indonesia towards a more ecologically responsible and socially inclusive path into the future.
While the global construction of dams and weirs has increased food production, energy sufficiency and water security, it has significantly reduced river health, fish populations and fish diversity. The impacts on fish and their habitats are leading to decreased biodiversity, reduced fish catches and smaller incomes of local fishers and these are all significantly impacting livelihoods. The Indonesian government has invested heavily in developing water infrastructure and so far, thousands of dams and weirs have been built to irrigate agriculture and generate hydropower. But the proliferation of this infrastructure is becoming increasingly associated with declining river health, negative biodiversity outcomes and human impacts.
Globally, technical solutions, such as fishways, are often constructed to mitigate the impacts of dams and weirs. These have varying degrees of success depending upon the design principles, target species and level of investment into mitigative technology. Across Indonesia, presently, there are only two infrastructures that have been equipped with fishways as an engineering solution to connect fish migration pathways. One of these sites, the Perjaya Dam, which is equipped with a pool and weir fishway, was selected in this study to examine whether the dam has an impact on fish populations and whether the existing fishway is adequate.
The work in this thesis sought to link together the ecological, people and engineering aspects of dam and weir construction to build a multi-disciplinary understanding of the impacts on fish. It sought to bridge several key knowledge gaps needed to “mainstream” the consideration of fish in river infrastructure planning and assessment.
Although many dams and weirs have been constructed in Indonesia, their potential impact on fish populations has not been studied. My research sought to understand if dams and weirs impact fish populations and the livelihoods of local communities. In addition, I examined the effectiveness of the existing fishway at the Perjaya Dam to understand whether fishway performance is sufficient to facilitate fish movement and also assess whether fishing activities within the fishway reduce passage success.
I took a mixed methods approach, combining ecological and social data to gain a holistic overview of the impacts of the Perjaya Dam. My methods took three forms as follows:
(a) Ecological impacts of the Perjaya Dam:
The first line of inquiry was to build the evidence base that dams and weirs can impact fish ecology. I hypothesized that, 30 years following construction of the Perjaya Dam, which included a fishway, that there should be few differences in fish community structure, upstream and downstream, if the fishway was working adequately. I used standardized experimental fishing methods to examine the fish community differences upstream and downstream of the Perjaya Dam to determine if there were significant differences in fish community structure that may be attributed to the presence of the dam. I surveyed fish community at multiple sites, using three different fishing gears (gillnets, castnets, and bait traps) upstream and downstream of the Perjaya Dam in the Komering River. Sampling locations were at 0 km, 1 km, 5 km, 10 km, and 20 km from the dam, both upstream and downstream. Spacing the sampling sites at this distance aimed to make sure the reservoir effect did not bias data collection.
(b) Social understanding of importance of fish and perceptions of the dam:
The second line of inquiry was to understand the dependence of local fishers and households on inland fisheries. It has long been suggested that Indonesian households have a strong dependency on fisheries, but this has not been empirically demonstrated. Working with communities in the Martapura district, South Sumatera, I interviewed a range of “key informants” from a range of difference industries to understand the importance of the fishery and whether locals perceived that the dam has facilitated any changes to the Komering River. Data collection was divided into a two-stage process starting with interviewing key informants using semi-structured interviews, followed by a questionnaire survey with fisher household respondents. The key informant interviews aimed to elicit key themes and understanding of the local, national, and regional contexts and the importance of fisheries in the Komering River region. The findings from the key informant interview data aided in the development of the questionnaire survey and to understand the importance of fisheries to local people and perceptions of local people of the changes in the river and fisheries since the Perjaya Dam construction.
(c) Ecological survey of a technical solution (fishway) to attempt to mitigate the dam effects:
The third line of inquiry was an ecological investigation into the effectiveness of the Perjaya Dam fishway. The combined impacts of the fishway design and fishing pressure in the fishway may be having a significant impact on fishway success, and subsequently on fish biodiversity upstream of the dam. Here I aimed to determine if the pool and weir fishway at the Perjaya Dam was working effectively in facilitating upstream fish movements. I hypothesised that the implementation of a Japanese fishway design, combined with intensive capture fisheries, would lead to sub-optimal passage success at the site. Fishway trapping in the bottom and top of the fishway was performed in the presence and absence of fishers was conducted to evaluate fishway success. The results will provide valuable insights into whether the design of the fishway and/or fishing pressure significantly impacts the success of fishways.
The ecological studies conducted in the Komering River revealed a strong decline in fish populations and a loss of species diversity following the construction of the Perjaya Dam. This indicates a direct and long-lasting impact on the river’s aquatic ecosystem. The dam’s presence obstructed fish migration routes despite the presence of a fishway. Key results included that 13 of 36 species were found only downstream of the dam and five of 36 species were found only above the dam. There were significant differences fish community composition between upstream and downstream regions using either fish abundance, species richness or species diversity as the response variable.
The key informant interviews and questionnaire found people reported fisheries played a crucial role in the local economy, with fish being a primary source of income for households in the region. Furthermore, fish were found to be the primary source of protein in the diet of the local communities. The decline in fish populations caused by the dam’s construction was perceived to have had severe socio-economic consequences for these communities, affecting their food security and livelihoods. The social surveys conducted among local fishers and communities revealed a consensus that the Perjaya Dam had contributed to the losses in the fishery. The negative perceptions were echoed by local stakeholders who called for improved legislation and better compliance measures to address the issues faced by the fishery. The need for effective policies to restore and sustainably manage the fishery resources was evident.
Key findings included that fishing activities are vitally important for generating income, consumption, and fish are the main source of protein for the respondents, particular for the poor who rely on fish for their crucial income and food sources. They often consume small fishes whole, this is a rich source of calcium and other essential elements. The presence of the Perjaya Dam was perceived by respondents to negatively impact fish populations and their habitats. Therefore, any planned dams should be carefully considered even with a fishway because I found a strong evidence of fish community fragmentation between upstream and downstream the Perjaya Dam. In addition, the respondents believed that there is lack of involvement of fisheries sector in water infrastructure development planning and management that leads to natural resources degradation.
One attempt to mitigate the dam’s impact was the implementation of a fishway, designed to facilitate fish migration and maintain the ecological connectivity. However, a carefully controlled fishway trapping study revealed that the fishway was not successful in fulfilling its intended purpose. One of the primary reasons for its failure was that it was designed for Japanese fish species, which differed from the indigenous Indonesian fish species in the Komering River. There were various other principles of best practice fishway design including understanding of local hydrology and hydraulics which had been omitted by the designers. Additionally, local fishers actively exploited the fishway as a fishing ground, further reducing fish populations and compromising the fishway’s functionality.
My results found that the Perjaya Dam fishway is successfully passing 27 species and a diverse range of size classes. However, eleven species were not able to ascend the full length of the fishway. Collectively, our results suggest some modifications to future fishway designs are needed for Indonesian fishways to improve fishway efficiency for fish species that are threatened by dams.
The outcomes of this research highlight the urgent need for comprehensive measures to address the ecological and social challenges posed by the Perjaya Dam on the fisheries of the Komering River. I emphasize the importance of integrating ecological research with socio-economic studies to devise effective strategies for sustainable fisheries management. Furthermore, the study highlights the significance of considering local contexts and indigenous species when implementing interventions like fishways. My findings provide valuable insights for related stakeholders such as policymakers, environmental agencies, and local communities to collaboratively develop and implement appropriate conservation and management measures to restore and protect the fisheries of the Komering River, and rivers in Indonesia more broadly. It is my hope that this research contributes to the ongoing dialogue on sustainable river management and helps steer Indonesia towards a more ecologically responsible and socially inclusive path into the future.
Original language | English |
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Qualification | Doctor of Philosophy |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 07 Feb 2024 |
Place of Publication | Australia |
Publisher | |
Publication status | Published - 21 Feb 2024 |