Lakes resist the introduction of new fish

November 9, 2015 by Ingrid Söderbergh, Umea University
Lakes resist the introduction of new fish
Credit: Anna Henriksson

In her dissertation, Anna Henriksson presents a new method of establishing how freshwater fish can defend themselves against an invasion of a new fish species. The method takes into account that resident species in a lake contribute at a varying degree to the resistance of the new species. The dissertation defence takes place on 12 November at Umeå University.

The introduction of new in an ecologic community can change ecosystems for instance through loss of native species and functions of the ecosystem. Biotic resistance is a concept describing how well the ecologic community can resist invading species and prevent the establishment of new ones. This is achieved either by strong competition between resident species and new species or by residing species predating on the new species.

In her dissertation, Anna Henriksson uses a large dataset from more than 1,000 failed and successful introductions of in Swedish lakes to test hypotheses surrounding biotic resistance. A general hypothesis in biotic resistance is the one of . It predicts that species rich communities are more resistant to invaders than species poor communities as more species can use up a larger proportion of the resources. The hypothesis has not been supported in empirical studies and one important reason is that it assumes that all species contribute to an equal level of resistance and that all have a on the new species' ability to establish.

Anna Henriksson presents a new method in estimating species richness which better reflects the ecological community's resistance. The method, which she calls weighted species richness, takes into consideration that resident species contribute in different strength to resistance, but also that residing species do not necessarily have a negative impact on the establishment of the new species, but can also have a positive impact.

"My results show that this method of estimating the resistance predicts the success of the introduction better than the classical hypothesis. This means that the specific interactions the established fish species have with other fish species determine the outcome of the introduction," says Anna Henriksson.

Furthermore, Anna Henriksson has explored how the resistance in a lake has developed over time through analysis of ' achievement in its part as both invading and residing species.

She was able to see how species' ability to establish and their resistance correlated positively. Resistance will be built up over time through the species that most easily establish, such as pike and perch, also contribute the most to resistance to other species.

Arctic char and brown trout are two of the weakest species with low ability to establish and low . Anna Henriksson found that such species are also most sensitive to extinction when establish. This is of great importance to nature conservation, she continues.

"This means that Scandinavian mountain lakes that to a great extent are composed of weak species such as Arctic char and brown trout are sensitive to introductions of species such as pike and perch. If the char and trout populations are lost, they are also more difficult to reintroduce," says Anna Henriksson.

Explore further: 'Common' animal species are not that common and rare species are rare

More information: Biotic resistance in freshwater fish communities: … 3A861777&dswid=-8091

Related Stories

All species, great and small, must be preserved

October 27, 2015

Researchers warn all species are important, and conservation efforts should be based on the need for biological diversity and not on how useful individual species are to people.

North American freshwater fishes race to extinction

August 10, 2012

North American freshwater fishes are going extinct at an alarming rate compared with other species, according to an article in the September issue of BioScience. The rate of extinctions increased noticeably after 1950, although ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

EPA adviser is promoting harmful ideas, scientists say

March 22, 2019

The Trump administration's reliance on industry-funded environmental specialists is again coming under fire, this time by researchers who say that Louis Anthony "Tony" Cox Jr., who leads a key Environmental Protection Agency ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.