A novel molecular genetic analysis evaluates the impact of river restoration activities on brown trout populations in Estonia, demonstrating that one of the most highly priced fish species among fisherman readily benefits from the restoration of spawning grounds by volunteers.
An analysis on applying techniques that have never been used in researching fish before assures that the efforts of Estonian volunteers trying to restore the trout’s spawning grounds to guarantee successful reproduction have not been in vain.
“We combined molecular genetic analysis with a novel statistical analysis to answer the practical question of how well are the newly restored brown trout spawning grounds functioning compared to areas where natural reproduction occurs,” says Anti Vasemägi, researcher at the Estonian University of Life Sciences. “To our surprise, very little research has been conducted on how the restoration of the spawning grounds and nursery habitats affects trout populations. In fact, this study is one of the first to convincingly demonstrate the added value of DNA analysis in monitoring the abundance and status of wild fish populations.”
To gather the necessary material for analysing the fish’s DNA, Vasemägi and his colleagues monitored the abundance of juvenile trout in sixteen rivers and streams over two years, spending days on local rivers in Estonia, catching small fish and cutting off tiny pieces of their fins for DNA analysis before releasing them back into the rivers.
“We used a molecular technique similar to that which is widely used to identify paternity in humans. DNA can be used as a fingerprint, and it allowed us to estimate how many of the fish within a stream were siblings and how many were half-brothers and half-sisters,” Vasemägi explains. “This information enabled us to estimate how many adult fish have successfully reproduced in restored and natural spawning grounds.”
The motivation to apply cutting-edge molecular methods to analyse trout populations came from practical life. First of all, fishermen are always keen to know how much fish there is in a certain river. Secondly, ever since 1999, volunteers have been actively restoring and building new artificial spawning grounds for trout because of the shortage of high quality spawning grounds in Estonian rivers. Over the years, volunteers have made a considerable effort, and a significant amount of resources has been spent on these projects, but, until today, it was not known how efficient these habitat restoration actions actually were and how much the restored spawning grounds increase the production of juvenile trout in our rivers and streams.
“The similar juvenile density and estimated number of breeders in restored and undisturbed natural spawning and nursery grounds indicate that brown trout quickly take advantage of recently restored spawning habitats,” says Vasemägi. He added that this is good news for river restoration projects, as the restored spawning grounds are expected to increase population abundance and the carrying capacity of trout rivers.
“Combined with ecological work, our approach can be used to further pinpoint the biotic and abiotic factors that negatively affect the abundance of trout in our rivers and streams,” Vasemägi explained.
This article was first published on Research in Estonia website.
Editor: M. Oll