Decline in native fish species -- Invasive species on the increase

October 01, 2018

The majority of Bavaria's watercourses are in poor ecological condition. A team from the Technical University of Munich (TUM) has now conducted the first systematic analysis of long-term data on fish stocks in the Upper Danube, Elbe and Main rivers. The team concluded that native fish species are on the verge of extinction, while the populations of some invasive species are increasing.

On behalf of the Bavarian State Office for the Environment and financed by the Bavarian Ministry of the Environment, the scientists analyzed all available fish data sets for the Bavarian catchment areas of the Danube, Elbe and Main rivers over a period of more than 30 years. They compared the current status with the historically derived reference status of the originally occurring species at the respective locations.

The study, published in the October issue of the journal Biological Conservation, shows that native character species such as grayling, after which a river region was named, have suffered massive losses in terms of both area and numbers compared to their historical reference status.

A similar picture emerges for other specialized fish species whose habitats are severely affected by siltation, higher water temperatures and dammed water bodies. Many of the particularly endangered species have complex lifecycles and are dependent on special conditions during different life phases. "If these special conditions no longer exist, or if the animals cannot migrate between sub-habitats, then they will have problems," says Dr. Melanie Müller from the Department of Aquatic Systems Biology at the Technical University of Munich and author of the study.

Formerly widespread species are strongly declining today.

A new result of the study is also that species such as the "common dace", which were previously regarded as widespread, are also declining compared to the historical reference status. In contrast, those species known as generalists, which demand very little from their habitat, are now propagating even more. Notable among these species are many non-native fish which were either deliberately imported to Central Europe, such as the rainbow trout or the topmouth gudgeon, or which arrived unintentionally via the ballast water of ships, such as the Pontocaspian goby species.

"In the future, we will have to be prepared to encounter increasing numbers of water bodies with new biological communities consisting of a mixture of species that would never naturally meet," says Prof. Jürgen Geist, professor at the Department of Aquatic Systems Biology and head of the study.

For this reason, systematic long-term analyses of the distribution and abundance of aquatic species are important: "The conservation of species and biodiversity must not stop at the water surface and should be based on scientific results," says Prof. Geist.
-end-
Publication:

Mueller, M., Pander, J., Geist, J.: Comprehensive analysis of > 30 years of data on stream fish population trends and conservation status in Bavaria, Biological Conservation 226; 311-320, 2018. DOI: https://doi.org/10.1016/j.biocon.2018.08.006

Contact:

Prof. Dr. Jürgen Geist
Technical University of Munich (TUM)
Chair of Aquatic Systems Biology
Tel: +49 (8161) 71 - 3767
E-Mail: geist@wzw.tum.de

Technical University of Munich (TUM)

Related Invasive Species Articles from Brightsurf:

The invasive species that Europe needs to erradicate most urgently are identified
An international research team analyzed the risk impact and the effectiveness of possible erradication strategies for invasive species already in the region as well as those that have yet to arrive

Crayfish 'trapping' fails to control invasive species
Despite being championed by a host of celebrity chefs, crayfish 'trapping' is not helping to control invasive American signal crayfish, according to new research by UCL and King's College London.

Climate change is impacting the spread of invasive animal species
What factors influence the spread of invasive animal species in our oceans?

Invasive alien species may soon cause dramatic global biodiversity loss
An increase of 20 to 30 per cent of invasive non-native (alien) species would lead to dramatic future biodiversity loss worldwide.

Protected areas worldwide at risk of invasive species
Protected areas across the globe are effectively keeping invasive animals at bay, but the large majority of them are at risk of invasions, finds a involving UCL and led by the Chinese Academy of Science, in a study published in Nature Communications.

Charismatic invasive species have an easier time settling into new habitats
An international study, in which the University of Cordoba participated, assessed the influence of charisma in the handling of invasive species and concluded that the perception people have of them can hinder our control over these species and condition their spread

Invasive species with charisma have it easier
It's the outside that counts: Their charisma has an impact on the introduction and image of alien species and can even hinder their control.

Invasive species that threaten biodiversity on the Antarctic Peninsula are identified
Mediterranean mussels, seaweed and some species of land plants and invertebrates are among the 13 species that are most likely to damage the ecosystems on the Antarctic Peninsula.

Research networks can help BRICS countries combat invasive species
BRICS countries need more networks of researchers dedicated to invasion science if they wish to curb the spread of invasive species within and outside of their borders.

Look out, invasive species: The robots are coming
Researchers published the first experiments to gauge whether biomimetic robotic fish can induce fear-related changes in mosquitofish, aiming to discover whether the highly invasive species might be controlled without toxicants or trapping methods harmful to wildlife.

Read More: Invasive Species News and Invasive Species Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.