Neobiota are organisms that have not been living in a certain area before and only got there through human influence. Thea are therefore non-native (or alien) with regard to that area. Neobiota can be animals (neozoa), plants (neophyta) but also micro-organisms such as fungi or bacteria. Some of these non-native species have undesirable effects on native species, habitats or ecosystem functions. In this case, they are called invasive.

Since the beginning, species are spreading from area to area: by migration or passive transport, e.g. with water or wind. Are the environmental conditions in the newfound habitat all right, they are able to colonize and to reproduce. As an example, Europe often was (re-)colonised by new or returning species after the ice ages.

Due to anthropogenic effects, these kind of migrations are strongly accelerated. Some animal or plant species are spread intentionally as ornamental or production species, or unintentionally (e.g. with ships or as seeds). Many species travelled from their area of origin to distant continents this way.

Species that were introduced in ancient times, are referred to as archaeobiota while more recently introduced species are referred to as neobiota. There are different definitions of this so-called “recent times” but in Germany the crucial year to officially differentiate between archaeo- and neobiota is 1492.

Some neobiota are unobtrusive. These species are part of flora and fauna without causing damage, like the freshwater jellyfish Craspedacusta sowerbyii, the mandarin duck (Aix galericulata) or the potato (Solanum tuberosum).

But other neobiota are able to spread really wide and fast, endanger native species, transport new deseases, can change whole ecosystems or cause economic damage. These species are called invasive neobiota. Most of them were introduced more or less recently during industrialization or globalization to new regions, river catchment areas or continents. This process of transportation as well as the establishment of invasive species is called biological invasion.

Examples of invasive species in Germany and the Czech Republic are

Humans use rivers and streams in many different ways – and often quite intensively. Channels between formerly separate river catchment areas, international shipping as well as global trade are promoting the introduction of invasive aquatic species, e.g. fish, mussels and small crustaceans from the Ponto-Caspian region or American crayfish species.

There are various transport pathways:

• as „stowaway” in or on boats and ships (ballast water, biofouling/ growing on ship hulls and screws),
• as fishing bait,
• release of exotic aquarium pets,
• intentionally stocking (in order of economic benefits),
• carrying of eggs, (e.g. by birds),
• upstream by active migration or downstream by drift,
• active migration over land

After the last ice age, biodiversity in Central European rivers was low. The European fish fauna, for example, still bears less species than one of other continents that were not buried under ice (e.g. North Amerika). Most of the waters had to be recolonised – and fish and flying insect were the firsts, while less mobile invertebrates came after. Because of this, the original diversity of crayfish, for example, was never restored (Thienemann 1950).

THIENEMANN, A. (1950): Verbreitungsgeschichte der Süßwassertierwelt Europas. Die Binnengewässer 18, 809 S., Stuttgart.

Additionally, in densely populated Central Europe, most of the aquatic ecosystems are under heavy human influence. Some of the factors complicating the life of many aquatic organisms and therefore reducing biodiversity are:

• Exposure to plant nutrients (fertilizers) and other pollutants (e.g. from wastewater)
• Increasing water temperature through to power plants or the release of industrial cooling water
• Less river continuity trough to hydropower plants or locks
• Structural degradation of water bodies and therefore less different habitats through to modifications for shipping and flood protection.

Extreme events as floods (e.g. 2002 and 2013 in Elbe river) or droughts (e.g. summer 2003 and 2019 in Elbe river) or environmental disasters (e.g. fire at the Sandoz chemical plants in 1986 in Basel at River Rhine), are further reducing the biodiversity in our streams. It takes many years for river ecosystems to recover from such incidents.

Many invasive neobiota are especially robust and therefore they are able to colonize disturbed water systems or extreme habitats. Thus, one could say, all of these newly established mussels, crustaceans etc. are increasing the biodiversity. However, several of these non-native species are causing additional loss of native species due to high competition (e.g. about necessary food resources or already less available habitats). Because invasive species often have high reproduction rates, these species reach a high number in no time and can endanger native species in their newly populated habitat. Often, artificial structures and modifications for shipping and flood protection provide suitable habitats for these newly introduced species while native species are missing suitable habitats as retreats.

But invasive neobiota are not only found in Central Europe. As here, alien species have been or are being introduced intentionally and unintentionally all around the world and sometimes cause great ecological and economic damage. Especially, islands, which often have a particularly large number of endemic species, are severely hit by the introduction of invasive species. This is why some countries have very strict regulations in order to prevent further invasive species (e.g. in New Zealand).

It is practically impossible to eradicate invasive neobiota once they are established. But for a useful management of these species it helps to recognize invasions early and restrict it as far as possible. Furthermore, maintaining or recreating retreat areas for native species can be of help. By river restoration and protection of near-natural river systems, suitable habitats of native species are preserved, which means that invasive neobiota may spread less explosively (because of higher competition) and their negative effects can be limited. Cross-border cooperation is important, as rivers and the species living in them do not know about borders. To do this, new strategies and solutions must be created. With the project MoBI-aqua, we want to contribute to this.

But you can help, too:

• Do not release alien species into the wild: exotic aquarium and pond pets do not belong in local waters!
• Avoid carryover: clean your fishing gear, buckets and boots/ waders before moving to another angling place.
• Clean your boat before relocating to another water body.
• Identify invasive species, distinguish them from native ones and report finds and observations, e.g. using the MoBI-aqua app.
• In some countries there are laws requiring removal of invasive neobiota according to EU-regulation. However, when in doubt, animal welfare and fishing regulations are dominant – catch up on laws and rules!
• Catches or live finds of neozoa must not be taken away or killed without fishing license and … of the respective country or state administration. However, rightfully caught gobies may be used for soup – recipes see Downloads.
• Last not least, everyone can help protecting habitats for the endangered biodiversity and mitigating climate change: Calculate your ecological footprint…