New Red List of freshwater fish and lampreys in Germany
In 2009, the trout (Salmo trutta) was classified as "least concern" nationally. Now its populations are declining in many federal states. For IGB researcher Christian Wolter, this is the first clear warning sign of major climate-related biodiversity changes in German watercourses. | © Shutterstock 2344359287
The Red List of freshwater fish and lampreys in Germany has been updated for the first time since 2009. It shows a clear negative trend over the last 14 years: 21 species have been classified threatened. This means that more than half of the native species are now considered threatened or already extinct. The trout (Salmo trutta), for example, experienced a negative reassessment, being classified from "least concern" to "endangered". With 10 per cent of fish species extinct, Germany is well above the European average of 2.5 per cent. According to fish expert and co-author Dr Christian Wolter from IGB, the causes include the loss of habitats due to river regulations and pollution as well as the consequences of climate change.
As the Red List shows, freshwater fish and lampreys are among the most endangered animal groups in Germany: 52 per cent, i.e. 47 out of 90 established native species, are currently classified as threatened or already went extinct or lost. Only 36 per cent are considered of "least concern". The remaining species are either "extremely rare" (4 per cent), "near threatened" (7 per cent) or cannot be classified ("data deficient", 1 per cent).
21 species were upgraded to a threat category
More species are currently classified in threat categories than in 2009; 21 species had to be upgraded by one or more categories. A total of 38 species are categorised threatened according to the new list, compared to 22 species in 2009. "We see a very clear deterioration in the conservation state of native freshwater fish and lampreys over the last fourteen years," said IGB researcher Dr Christian Wolter, one of the main authors of the German Red List.
The causes have long been known: Habitat loss, transverse structures, climate change
The reasons of endangerment include water pollution as well as river regulations and bank enforcement. As a result of these interventions, many waters lack shallow littoral areas land inundated floodplains serving fish spawning and nursing. Transverse structures such as weirs and dams, interrupt migration routes and also cause the decline of many species. The effects of climate change, such as increasing drought, higher water temperatures and less oxygen in the water, are also responsible for the decline of freshwater fish and lampreys.
"For most freshwater fish and lampreys, the main pressures as well as suitable mitigation and protection measures are well-known for long time. But water bodies are still not recognised as important habitats. A major problem is that we as a society often prioritise other functions, especially those of watercourses: Flood protection, shipping, drainage, wastewater discharge, power generation, water extraction and heat discharge are more important than ecological criteria," said Christian Wolter.
Political instruments are in place, but implementation is slow
With the entry into force of the Flora-Fauna-Habitat Directive in 1992 and the European Water Framework Directive in 2000, and the mandatory requirement that fish fauna be assessed as a biological quality criterion for the ecological status or ecological potential of water bodies, the causes of failure to meet targets have been systematically and comprehensively recorded. However, implementation of the WFD is slow.
According to the authors, socio-economic conditions and conflicts of use often hinder effective protection and revitalisation of water landscapes. "Under these conditions, the distribution patterns and population sizes of freshwater fish and lampreys have often stabilised at a low level after a temporary recovery, which leads to the large number of threatened species on the Red List," explained Christian Wolter. Germany is not doing particularly well in a European comparison: with 10 per cent of fish species extinct, the country is well above the European average of 2.5 per cent.
Brown trout: from stable populations to endangered status
A prominent example of the increasing threat of freshwater fish is trout (Salmo trutta) referring to brown trout, lake trout and sea trout. These are different life strategies of the species Salmo trutta, which are not reproductively isolated.
In 2009, it was still categorised of "least concern" nationwide, partly because its short-term population trend was stable at the time. As with other species, this positive trend came to a hold or is now estimated to be in decline in five federal states - including Bavaria and Baden-Württemberg, two federal states hosting the largest populations. Together with the change in the long-term population trend, this has resulted in a category change to "endangered".
"This change in assessment from stable populations to category 3 and thus to predominantly declining populations of this species, which is so widespread and common in Germany, is due to watercourse development and is certainly also a first clear warning signal for major climate-related biodiversity changes in riverine systems," said Christian Wolter.
Sturgeons: 7 out of 8 sturgeon species found in Europe are critically endangered, in Germany only the sterlet still exists without stocking
Sturgeons are particularly endangered: seven of the eight sturgeon species occurring in Europe are "critically endangered" throughout Europe, while the eighth is now considered "endangered". The last European specimens of the spiny sturgeon (Acipenser nudiventris), which has now been declared globally extinct, swam in the Danube. According to the current Red List, the European sturgeon (Axipenser sturio) and the Baltic sturgeon (Axipenser oxyrinchus) are still classified as "extinct or lost" in Germany. The populations can only be preserved through stocking measures, which are coordinated by the IGB in Germany.
The Danube sturgeon beluga sturgeon (Huso huso), starry sturgeon (Acipenser stellatus) and Russian sturgeon (Acipenser gueldenstaedtii) only reached the German Danube from the Black Sea very sporadically as early as the 19th century. Even then, the stocks were severely affected by overfishing. Today, all three species are "extinct or lost" in Germany.
Only the sterlet (Acipenser ruthenus) has a small population, which is probably self-sustaining even without stocking. Historically, the species was found throughout the entire German section of the Danube and in the lower reaches of its larger tributaries. "In terms of the precautionary principle, however, stable populations cannot be assumed," said Christian Wolter.
Atlantic salmon "near threatened" worldwide, stocks in Germany still "critically endangered" despite stocking
The current Red List for Germany still lists the Atlantic salmon (Salmo salar) as "critically endangered". The animals that are caught in German marine areas mainly come from stocking programmes. In North Rhine-Westphalia, Baden-Württemberg and Saxony, however, there is cautious optimism that salmon stocks there may not become extinct even without stocking programmes. The reintroduction programmes in the upper Elbe and Rhine could therefore be successful. However, the populations are far from stable. "The passability of rivers for migratory fish such as the Atlantic salmon must be further improved, also to mitigate the threat posed to this cold-loving species by climate change," recommended Christian Wolter.
This assessment is also supported by the current global assessment by the International Union for Conservation of Nature and Natural Resources (IUCN): As of this year, it classifies the Atlantic salmon as "vulnerable" worldwide on its Red List. Global populations declined by 23 per cent between 2006 and 2020.
Alpine bullhead, allis shad and Pearlfish: rays of hope mainly due to stocking and renaturation
While the Atlantic salmon was reintroduced to Germany through stocking measures, the reintroduction projects carried out with great commitment over many years have also brought initial success for three other species that were considered extinct or almost extinct in Germany in the 20th century: Alpine bullhead (Cottus poecilopus), allis shad (Alosa alosa) and Pearlfish Rutilus meidingeri.
The only historically known German population of pearlfish became extinct in Lake Chiemsee at the beginning of the 1990s following a sustained decline in stocks. Stocking measures since 1995 have been successful, with the result that a self-sustaining population of this extremely rare species has now developed and appears to be continuing to grow. There are also indications that a population has been maintained in the Danube. "These successes show that stocking can be suitable. However, the populations will only sustain in the long term when we finally prioritise water protection and restoration," said Christian Wolter.
Invasive round goby: fish with the most stable population increase
The species inventory of freshwater fish has also changed significantly since 2009 due to the establishment of seven additional alien species in Germany, raising their total number to 21. However, none of these fish species newly established since 2009 has significantly spread yet.
On the other hand, four of the alien fish species established before 2009 are widespread and regionally common: goldfish (Carassius auratus), stone moroko (Pseudorasbora parva), pumpkinseed (Lepomis gibbosus) and round goby (Neogobius melanostomus). "The populations of these four species, which were established before 2009, have once again significantly increased in the last 14 years. Round goby in particular is spreading, but is presumably also being introduced by anglers and aquarists. In the quantitative analysis, it was the fish species with the strongest population increase," explained Christian Wolter.
Red lists always have a defined distribution area to which the endangerment assessment refers. The current Germany-wide conservation analysis of freshwater fish and lampreys assessed 90 established native species based on their actual population state, long-term and short-term population trends as well as existing risks. The German Red List is based on the country-specific assessments of 59 experts from all federal states. It was supported by a quantitative evaluation of fish sampling data from 6,424 monitoring sites from the monitoring programmes of the European Water Framework Directive and the Habitats Directive as well as findings from other scientific studies.
