The most important indicator of ecosystems health of river basin of Rize city which is known to be rich in fresh water potential isthe natural trout stocks in Eastern Black Sea. Therefore, the determination of distribution areas of natural trout living in Eastern Black Sea and especially Rize river basins of Turkey, In particular in Rize province, it is necessary to determine the distribution areas, living habitats, spawning areas, risks and threats in terms of protection of species in each stream. In this study, the abundance of natural trout stocks living in Rize river basins, anthropogenic processes and interactions with hydroelectric power plants are emphasized. It is known that there are 9 kinds of natural trout species belonging to the Salmonidae family represented by 29 different species throughout Europe and three species live in the fresh waters of the Black Sea region. The Black Sea trout (sea trout: Salmo coruhensis) is an endemic natural trout species of the Eastern Black Sea basin, which is known to grow the best between all trout species and to migrate and propagate between the sea and the fresh water. On the other hand, Salmo rizeensis, is a red-spotted trout species that lives in the upper parts of large river systems, preferring sloping and fast flowing river habitats, also known as mountain trout.
The natural trout stocks' population structure, bio-ecological characteristics and fish abundance have been the most curious topics of river basins,
since the river ecosystem health is due to the fact that the natural trouts are on top of the food pyramid of the river ecosystem. In this study, the population structure, distribution areas and life habitats of natural trout species living in Rize province freshwater sources were determined and measures to be taken in order to remove the elements affecting and threatening them were tried to be revealed. For this purpose, 93 samples were collected in 25 streams in 8 river basin. Water sampling and habitat observations were performed besides fish sampling performed by electro-shock and scattering. It is seen that large rivers generally scattered sea trouts together with different species in the lower basins, and mountain trouts spread in the upper parts. In some small rivers, only sea trout and other species life but no mountain trout are interesting findings. In the study, it was determined that the main factors affecting natural trout stocks are domestic and industrial wastes, agricultural interactions, HPPs and stream bed modifications. Particularly the modification of roads, walls and bridges etc. and processes of construction in the river beds, and operational
stages of HPPs have been observed to pose a significant risk to the reproduction, nutrition and habitat of natural trout stocks. In the basins of the river basins of Iyidere-Ikizdere, Salarha and ÇayeliBüyükdere, the significant reductions in fish stocks in the areas where the HPPs and river bed modifications are made demonstrate how effective these factors are.As a result of the study, the protection of natural trout stocks in the region should be ensured with the protection of the areas with rich sea trout populations (natural area declaration), all kinds of activities should support natural life, purification of domestic, agricultural and industrial wastes, unnecessary modifications in river beds, the protection of coastal small waters preferred by the sea trout, the introduction of the correct habitat for local species, not introduction of foreign species for culture, and the isolation of culture species from natural waters very well, resulting in the lowest risk factors.