The decline of fisheries on the Madeira River, Brazil: The high cost of the hydroelectric dams in the Amazon Basin

The number of dams operating in the Brazilian Amazon region has grown at an increasingly rapid rate in recent years. Despite being considered beneficial by providing clean energy, hydroelectric dams’ plants have negative impacts on the ecological processes that are fundamental to maintaining ecosystem services and conserving biodiversity in the Amazon. In this context, this thesis aims to identify and evaluate the environmental impacts generated by the Santo Antônio and Jirau dams on the aquatic ecosystems and fisheries activity of the Madeira River basin. To fulfill this objective, this thesis was structured in two chapters. In the first chapter, the influence of the Madeira river hydroelectric complex on the local fishery stocks was evaluated. This study investigated the hypothesis that the instability of the flood pulse caused by the construction of the dams has caused a significant reduction in the fish stocks of the Madeira River. This hypothesis was tested using fishery landings data obtained in fishing colony (Z-31) “Dr. Renato Pereira Gonçalves ”, located in the municipality of Humaitá, Amazonas State, from January 2002 to September 2017. The collected data were daily recorded at the colony and include the fishing ground (point), the date of the beginning and the end of each fishing trip, type of fish caught and total catch (kg). This study indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. The results also point out that the decline of fisheries recorded for the Humatiá colony is mainly related to the increase of the Madeira River fluviometry average after the construction of the hydroelectric dams. In the second chapter, the impacts generated by the Madeira River hydroelectric complex were evaluated through the perception of local fishers (22 Men and 6 Women) and the fishery database from the Z-31 colony. This study aimed to investigate the environmental impacts generated by the hydroelectric complex in the Madeira River based on the perceptions of local fishers and fishery database, it focuses attention on three main points: (i) local fishery stocks; (ii) the fish and (iii) the aquatic ecosystems. The local fishers were selected through the “snowball” approach for the application of semi-structured interviews. All the fishers confirmed having perceived a decline in fishery productivity following the impounding of the Madeira River. Changes in fishes' conditions were also perceived by the local fishers, including exophthalmia (82%), a reduction in the weight or length of the fish (25%), and irregular breeding season (14%). Regarding impacts on the river, changes in the hydrological cycle were the process most frequently remembered (75%). The results of this thesis elucidate several environmental impacts caused by the implantation of hydroelectric power plants in the Madeira River and highlight the high risk of these enterprises for aquatic ecosystems, fishing activities, and Amazonian riverside populations. It is hoped that this thesis may help to prevent, mitigate or even fairly compensate for similar impacts both in other parts of the concerned river basin and in other basins in the Amazon region. Abstract Despite being considered beneficial by providing a clean and renewable source of energy, the construction of hydroelectric dams has extremely negative implications for Amazonian fisheries. This study investigated the impacts of the Santo Antônio and Jirau hydroelectric dams on the fishery stocks of the Madeira River. This investi-gation was based on fish catch data from the Z- 31 fishing colony, located in the municipality of Humaitá, in Amazonas State, Northern Brazil. Data were collected daily and provided information on the date of return from each trip, the fish species targeted, and the total catch (kg) between January 2002 and September 2017. The results indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. These results highlight the high price paid by local fish communities for the development of hydroelectric power in the Amazon basin. Mean variation in fishery production was calculated using: Δ P i = P Ai − P Bi (II) , where Δ P i = mean variation in fishery production between periods (before and after) in each month i , P Ai = mean fishery production after the damming of the river in each month i , and P Bi = mean fishery production before damming in each month i . The result of mean variation in fishery production was regressed on the classes recorded for mean variation in fluviometry. All statistical analyses were run using the software R 2.14. 1 (R Core Team 2011) (Sokal & Rohlf, 1995). ABSTRACT 28 The present study aimed to investigate the environmental impacts generated by the hydroelectric 29 complex in the Madeira River, Brazilian Amazon , based on the perceptions of local fishers and 30 fishery database, it focus attention on three main impacts: (i) on local fishery stocks; (ii) on the 31 fish; and (iii) on the aquatic ecosystems. The local fishers were selected through the “snowball” 32 approach for the application of semi-structured interviews. All the local fishers confirmed having 33 perceived a decline in fishery productivity following the impounding of the Madeira River. 34 Changes in the condition of the fish were also perceived by the local fishers, including 35 exophthalmia (82%), a reduction in the weight or length of the fish (25%), and irregular breeding 36 patterns (14%). In the case of impacts on the river, changes in the hydrological cycle were the 37 process remembered most frequently (75%). The results elucidated a range of environmental 38 impacts caused by the hydroelectric dams of the Madeira River. 39