Fish are unusually active animals changing their habitats over the seasons of the year with the aim of reaching particular stages of their life cycle. They reproduce in one place, their fry and young feed elsewhere and adult fish prefer other sites as their feeding grounds. The same applies to winter habitats of particular fish generations. Bearing all this in mind one has to protect the sites which are crucial to fish existence (spawning grounds, migration ways) as well as preserve periodical river floods as it is according to the natural rhythm of ebbs and flows that river ichthyofauna accomplish their life cycle. Disturbing or breaking this rhythm (in extreme cases) results in extinction or reduction of particular fish species (Wiśniewolski, 2003). In our times it is intended and unintended anthropogenic intrusions (apart from natural environmental conditions resulting from physical geography and natural influence of abiotic and biotic components) which have become of great significance to fish existence in river ecosystems (Wiśniewolski, 2002). As mentioned before river ichthyofauna is influenced by many various factors, however, it is the obstacle constructions on rivers that have their sweeping consequences on ecosystems in the long run – resulting in destruction of their ecological integrity.
The Rega basin is a relatively cohesive ecosystem. However, building a great number of hydrotechnical structures and excessive sewage disposal over a long period of time caused a significant decrease in its biodiversity. At present the amount of sewage dumped into the rivers has been decreased considerably which resulted in a significant improvement of water quality in some parts of the river channel. However, the hydrotechnical structures (often in bad condition) make it difficult or even impossible for fish to arrive at their spawning grounds or inhabit appropriate biotopes located in the upper course of the river. Although there are good, natural spawning sites, it is impossible or very difficult to access them (the Ukleja, Stara Rega or Rega upper courses). Such fish as brown trout or European lamprey arrive easily at Gryfice where they are hampered by the first hydrotechnical structures. It results in concentrating part of the migratory fish population in the vicinity of Gryfice. Only a small number of fish manage to get through and arrive at the tributaries of the Rega river located beyond Gryfice. The structures built in those locations make it impossible for fish to migrate upriver. This situation, lasting for many years, has had its negative impact on the biodiversity of the Rega channel and its tributaries.
Since 2005 the Rega river has been restocked with salmon Salmo salar which is of high priority to Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora. Over the last six years 121,440 fry of this species have been put into the river. Salmon reproduction and first stages of development take place in clear, cool and well-oxygenated rivers and streams. To spawn salmon need large stretches of gravel and rocky-gravel substrate where they dig out nests and hide eggs. It is a lithophillic fish species which requires good environmental conditions and the Rega river with its tributaries seems to satisfy those conditions. But due to the fact that the spawning grounds are not large enough to restock salmon it is necessary to clear spawning channels and create appropriate spawning grounds. It will gradually decrease the intensity of restocking and restore the salmon population.
In the Rega basin there are two NATURA 2000 protected areas within the framework of the Habitats Directive – the mouth of the Rega river – an area of 14,827.8 ha which covers nearly all the tributaries together with the Rega channel excluding the Łożnica and Gardominka rivers. The second area is the Brzeźnicka Węgorza which covers 592.2 ha.
A number of species mentioned in Annex II to Council Directive 92/43/EEC of 21 May 1992 were found in the protected areas. They include spined loach Cobitis taenia, European bullhead Cottus gobio, European bitterling Rhodeus sericeus amarus, river lamprey Lampetra fluviatilis, brook lamprey Lampetra planeri, although they often inhabit different areas. And what is interesting is that although there are appropriate habitats in those areas the species of fish that might inhabit them are now missing (including the ones mentioned in Annex II). By clearing the whole area of the Rega basin some wildlife corridors will be created. Thus we will enable those species of fish to migrate to the areas that are located far apart from each other and which are currently uninhabited by them. For that reason proper functioning of the Rega river ecosystem is of great importance to the biodiversity of the area with its huge potential currently not fully realized.
Therefore the main objective of the project is indirect environment protection and increase in the biodiversity of the water ecosystems protected by NATURA 2000 by way of linking them with a blue ecological corridor. The additional objective is to restock salmon population in the Rega basin. It is connected with the main objective and by no means less important.
Actions and means involved:
The abovementioned objectives will be reached by performing the following actions:
* clearing the Rega channel and its major tributaries by building the so called fish passes, but wherever possible we will use fish passes looking as near as possible to natural ones (riffles, fish ladders);
* creating artificial spawning grounds (spawning beds in effect) and enlarging the ones that already exist with their substrate content prepared mainly for salmonids;
* planting trees along 47 km of the river bank where there are now virtually no trees on either side, shaded areas will be created and as a result water temperature will decrease, which in turn will improve its quality.
* installing monitoring devices which will keep record of the fish migrating upstream and downstream. By means of the monitoring system it will be possible to determine what species migrate, how big their population is and what sizes they are.
* installing the so called electronic barriers at the sites where a specific result is expected, i.e. at Rejowice, Likowo, Gryfice and Płoty. The barriers are devices transmitting electric impulses of particular wattage which deter fish from entering the area where turbines of hydroelectric power station are located and guiding them in the direction of fish passes. The electric waves are strong enough to guide fish appropriately, but weak enough to do any harm. According to the research performed by Wrocław University Of Environmental And Life Sciences the barriers in question decrease fish mortality caused by the hydroelectric turbines down to 90-100%.
Expected results (outputs and quantified achievements):
1. By clearing the channel of the Rega river and its major tributaries the appropriate habitats will be inhabited by the fish which are now unable to access them.
2. By creating artificial spawning grounds, increasing the number of fish which inhabit the Rega river, and first of all by improving the population of Atlantic salmon (for several years the Rega river has been restocked with their fry) which have virtually no possibility to access the spawning grounds in the Rega basin.
Apart from clearing the Rega channel and creating artificial spawning beds we will keep record of the fish migration, which will allow us to specify when and where fish, salmon in particular, access the spawning sites in the Rega basin. As a result we will be able to perform more successful protective actions aimed at reproducing fish (at present most salmonids fall prey to poachers before they spawn). By installing the monitoring system at several strategic locations in the Rega basin a more effective quality control of fish restocking will be realized.
The main problems in the Rega basin (hydrotechnical structures on the river, lack of spawning sites) that this project aims to solve are typical of most of the salmonine rivers flowing into the Baltic sea. Implementing this project consisting of so many tasks integrated into one joint action will create a way and pattern with regard to re-establishing the whole water ecosystem in which the most valuable component is the migratory fish species. The project based on best practice implementation also includes actions which have never been performed on such a high scale in the West Pomerania province, i.e. installing the so called electronic barriers which will considerably increase fish population in the Rega river.
Furthermore, by creating blue ecological corridors we will be able to take indirect protective measures for NATURA 2000 areas which for many reasons are now isolated enclaves with limited possibility to perform various protective actions on a larger scale (improving biodiversity, re-establishing habitats, etc.).