In many freshwater lakes around the world, carp of all kinds are a common sight. These bottom-feeding fish can grow anywhere between two to three feet in length. They’re also an incredibly invasive species, and they appear to be having a negative impact on the bodies of water where they’re introduced.
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In particular, researchers based out of the University of Barcelona have noticed a significant decline in both diving ducks and waterbirds that hang out around the world’s freshwater lakes as a result of these carps’ presence.
Some of these, such as the white-headed duck (Oxyura leucocephala) and the common pochard (Aythya ferina) are listed by the International Union for the Conservation of Nature (IUCN) as endangered and vulnerable species respectively.
In the journal Biological Conservation, the researchers lay out the details for their case, which studied the effects of carp on diving ducks and waterbirds in lakes found in the Mediterranean region; namely, in the Medina and Zoñar lakes that are found in South-Western Spain
By tracking the ecosystem where common carp were introduced from 2001 to 2013, the researchers could establish a baseline and keep track of the effects of carp introduction on both waterbird populations and macrophyte cover; the latter was observed via satellite imagery.
What they had noticed were declines in as many as 69 waterbird species and/or diving ducks, while populations of fish-eating creatures, like herons, steadily increased in comparison.
In conclusion of the results that were observed, the researchers note that the introduction of invasive alien carp to non-native habitats poses a risk to countless existing waterbird and diving duck species and could be both dangerous and anti-productive in their conservation.
"The shallow lakes such as the ones in Medina and Zoñar are important lacustrine systems for the preservation of aquatic biodiversity in semi-arid regions such as the Mediterranean. Our scientific study concludes that there would be a severe impact on many water bird populations if all lakes were invaded by this exotic species," said Alberto Maceda Veiga, the study’s lead author.
To help resolve the problem, one of the only things we can do is try to control carp populations so that more waterbirds and diving ducks can thrive in their presence. Obviously, this also means preventing them from spreading to areas where they aren’t native.
An unrelated fact, carp are commonly eaten in countries around the world, but typically avoided as a food source in North America.