Today we celebrate World Fish Migration Day, which aims to highlight the need to preserve freshwater habitats and migratory species that are often threatened by the construction of dams and other negative human impacts on the environment. Biodiversity of freshwater fish is threatened in the world and in our country as well. Freshwater ecosystems suffer various negative consequences and have a negative effect on the survival of many species in these environments, which depend on the free flow of water, especially during spawning.
Migration is a departure from one habitat to another, both daily and seasonally, at a certain time of the year, but also at a certain age. Migrations occur either only once or several times in the life cycle of certain species. Most fish species migrate due to the need for reproduction, or spawning, but also due to the search for food or warmer habitats. Based on their movement, we distinguish species that move only in fresh water (potamodromous) and those that move only in salt water (oceanodromous). We also have species that live in both fresh and salt water (diadromous), depending on their life stage and needs. Species such as Pacific salmon (Oncorhynchus tshawytscha) live in saltwater and migrate and spawn in freshwater (anadromous). This species travels from 1,400 km to 3,000 km on its journeys, while also overcoming obstacles several meters high. On the way, they encounter various barriers, which are proving to be impossible to overcome during the last few decades and because of that this species suffered a drastic reduction in population. There are also species that live in rivers and reproduce in salt water (catadromous), such as the European eel (Anguilla anguilla). This species travels up to 10,000 km on its journey, because it crosses the distance, for example, from the Sargasso Sea, where it spawns, to the freshwater rivers of Europe, including the Balkans. There are also species that move between fresh and salt water, but not for reproduction (amphidromous). One of them is the Thicklip grey mullet (Chelon labrosus), which travels long distances for food and migration to warmer regions.
Over 11,000 species of fish migrate to successfully complete their life cycle. About 1,100 of these species are considered extremely special because they overcome extremely long journeys and encounter various obstacles in order to maintain their population, to survive but also to be an integral part of nature, a link in the chain that maintains balance. According to the data, we have come to a situation where only about 40% of the rivers in Europe are in good condition, and mostly all of them are headwaters which are untouched by man, who is the main culprit for the destruction of these freshwater ecosystems. In our country, many species of fish are in danger in terms of survival, some of them that migrate are salmon, pike, barbel, vimba, burbot, sterlet, perch and others. Today, migration is very difficult, the biggest problem is the construction of dams and hydroaccumulation, and there is also a poaching.
Based on the fact that many existing dams are a real physical obstacle and a problem for the life cycle of species, projects of putting water in pipes, building dams and physical barriers are still favored in our country. The waters are already polluted with untreated sewage wastewater, poaching is still present and various harmful projects on our wild natural rivers are still being encouraged.
The damage caused by the 119 small hydroelectric plants that have been built so far is catastrophic. Fish lanes do not work in practice, on many rivers we have a completely empty riverbed, and fish plagues are also often. A worrying fact for us is that up to now it is planned to build up to 500 small hydroelectric power plants in Bosnia and Herzegovina, and in the Balkans in general that number is up to 3,000. All this for the purpose of making money, to the detriment of nature and citizens.
Around 1.2 million dams and barriers have fragmented European rivers. Many of them are outdated and abandoned, and in some cases, they are even a century old. At least 150,000 are considered to be old, outdated and “unnecessary barriers”. All these fragmentations of watercourses affect the numbers of migratory fish populations, so in the last 50 years their numbers have dropped by as much as 93 percent, which is devastating. The European Union’s Biodiversity Strategy for 2030, which is part of the European Green Deal, is to create at least 25,000 kilometers of free-flowing rivers. The costs of restoring dams and barriers are significantly higher than the costs of demolition, so this is an efficient and cost-effective way to restore rivers.
For this purpose, it is necessary to protect our naturally clean and wild rivers, to preserve the blue heart of Europe, the rivers of Bosnia and Herzegovina, which are one of the few in Europe that are still intact, and which need the protection of ordinary people. In addition to the fact that we have enough energy produced by these power plants, as a society we should dedicate ourselves to preserving our rivers and the living world in them. The phenomenon of removing dams and their demolition is becoming more and more frequent worldwide. The leader in this is North America, where around 1,400 dams have been removed so far, while in Europe the total number has reached up to 4,500 different types of barriers. “Dam Removal Europe” (DRE) is an initiative that aims to reduce the number of dams in Europe and also to “revive” rivers. According to their report, during 2021, 239 dams were removed in Europe, which is a significant increase in this type of initiative in Europe, as this figure in 2020 was 101 removed objects. Spain had the largest number of removed dams last year, 108 of them, and also the largest removed dam (13 meters tall) was located in Spain. Finland is one of the most efficient countries in terms of removing river barriers. This Nordic country is removing even active hydroelectric power plants. For the first time last year, Portugal, Slovakia and Finland removed barriers in their countries. Montenegro is the first such case in the countries of the Western Balkans. They removed three dams on the Vezišnica River, all in order to improve the ecological status of the river.
Today is the day when we should stop and think about how we can influence the preservation of our nature, our rivers and our migratory fish species. If someone changes things for the worse, we should and must change things for the better. Let’s protect the rivers, let’s save migratory fish and all others. Let’s save the environment, because our survival depends on it.
Fish need passageways.
Happy Migratory Fish Day.
Freedom to rivers.