Due to the next season, during which there is a fish pass at the Smołdzino hydroelectric power plant, we decided to present you the results so far The main purpose of building the fish pass is to enable the free movement of fish by clearing the migration corridor. That is why in this article, we want to share the data collected so far.
However, first, it is worth recalling that for the analysis of the phenomenon of fish migration and species identification, the Biometric Fish Monitoring Station was installed on the upper station, in the first chamber. Monitoring of the movement of aquatic organisms in the fish pass is based on the HSMR hydroacoustic system. It uses two detection methods, the hydroacoustic based on hydroacoustic transducers and the optical method based on optical cameras
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Thanks to the monitoring system, we are able to determine how much fish flows through the fish pass. We can also specify the type of fish, its size and the direction in which it moves.
The most common species recorded by the monitoring system is sea trout. Currently, we have the results of two full migration seasons. According to the collected data, in 2020, 477 individuals passed through the pass, while in 2021, 266 individuals passed through the pass. Below the article, we present a graphical summary of the number of detections in the form of a graph, thanks to which it is easier to determine at which point in the migration season we received the most detections.
At the same time, we continue to collect and prepare data so that each migration season can be analyzed in its entirety. We are in the process of preparing a data sheet for the 2022 migration season, which we will also inform you about.
In addition to sea trout, we have examples of other species that use the structure in question. The fish pass is also used by cyprinid fish, as well as salmonid fry and brown trout. In order to show you the amount of fish of different species, below the article there is also a graphical representation of the amount of fish of different species migrating upstream 
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After two full research seasons, apart from the confirmed migration of sea trout against the current, the lack of any migration in the winter and the permanent presence of fry of salmonids in the summer and autumn, we did not observe any other trends based on the data obtained. It is worth noting that the dam in the form of hydroelectric power plant in Smołdzino has been operating for over 100 years, blocking the river. Therefore, the need to migrate for breeding or feeding purposes for species other than diadromous fish may occur only after some time.
At this point, we can confidently say that the fish pass serves its purpose. As proof of this statement, below the article we present a video in the form of a compilation of some of the generated detections, it is a great example that not only large migratory fish overcome the fish pass Fish Monitoring Station Detection Compilation.
A period of only a few migration seasons is too short a period to notice long-term trends in fish migration. In view of all the circumstances, it is worth mentioning that the next step will be to monitor the number of spawning nests on the section of the Łupawa River and its tributaries above the hydroelectric power plant in Smołdzino, and later to examine the spawning efficiency.
Seeing the effects of the work so far, we are determined to continue our efforts to improve the condition of habitats and species. Such activities are extremely important from the perspective of long-term effects that may lead to an increase in biodiversity in the Łupawa River.
