Tag Archives: dam

Using eDNA to Monitor Fish Dispersal

Environmental DNA is a hot topic in biomonitoring. But what is it exactly, and how can it be used to monitor the dispersal of a reintroduced fish species? (Image credit: Gunnar Jacobs, CC BY-SA 2.0, Image Cropped).

Guest post by Christopher Hempel

Using environmental DNA to monitor the reintroduction success of the Rhine sculpin (Cottus rhenanus) in a restored stream (2019) Hempel et al., PeerJ, https://peerj.com/preprints/27574/

The Crux

The term “environmental DNA (eDNA)” is currently booming in molecular ecology. But what exactly is this technological marvel? Essentially, eDNA comprises all DNA released by organisms into their environment, and originates from mucus, scales, faeces, epidermal cells, saliva, urine, hair, feathers – basically anything an organism might get rid of during its life. The eDNA can be collected from the environment, extracted, and analyzed to detect species using molecular approaches. As this is a very sensitive and non-invasive approach, it is a very hot topic for biomonitoring.

eDNA can be collected from any animal (in theory), but aquatic organisms in particular have been shown to be good target individuals (as eDNA is easiest to handle in water samples). Consequently, there are many studies using eDNA to monitor the activity of fish, reaching from the presence of invasive species to the effects of aquaculture. Here, we applied eDNA analysis to monitor a reintroduced fish species, the Rhine sculpin. The sculpin’s poor swimming ability make it useful as a bioindicator of the passability of streams and rivers. We wanted to investigate the potential of using eDNA to monitor the dispersal of the species in a remediated stream on a fine spatial and temporal scale.

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Resuscitating Australia’s Floodplains: Environmental Water

On the left, a thriving wetland. The right, an arid forest.

On the left, a thriving wetland. The right, an arid forest. (Image Credit: Sam Perrin, CC BY-SA 4.0)

I’m standing on the dry side of the Murrumbidgee floodplain in country Australia. I say dry side, because whilst I’m standing on the harsh, dusty platform of soil and desiccated leaves that is pretty standard for this area, 15 metres away there’s a thriving wetland environment. It boasts waterbirds, a flock of emus, thirsty kangaroos, and fish. All that’s separating the wetland and dry land on which I stand is a road, only about half a metre above water level.

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Trout Restoration in the Great Lakes: A Success Story

A Lake Trout, the species which was almost driven to extinction by overfishing and Sea Lamprey invasion, has now been restored in the Great Lakes

The Lake Trout, the species which was almost driven to extinction by overfishing and Sea Lamprey invasion, has now been restored in the Great Lakes (Image Credit: Cory Goldsworthy, MDNR)

Back in June this year, I was fortunate enough to attend the 9th International Charr Symposium, a conference which takes place every three to four years focusing on fish in the genus Salvelinus. The conference took place on Lake Superior, a site where the local Lake Trout population had previously been greatly reduced by overfishing and the invasion of the Sea Lamprey in the first half of the 20th century.

Yet the concerted efforts of the State, Provincial and Federal governments’ Fisheries Departments from the U.S. and Canada worked to successfully control the invasive Sea Lamprey species, and the native Lake Trout population was restored. I spoke with Don Pereira, Don Schreiner and Cory Goldsworthy of the Minnesota Department of Natural Resources (MNDNR) and Minnesota Sea Grant (MNSG) about one of the rare success stories of invasion ecology.

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Between a Dam and a Hard Place

Dams like this change the flow regimes of rivers, and prevent some species from accessing their spawning grounds, lowering population viability. But is removing them completely danger-free? (

Dams like this change the flow regimes of rivers, and prevent some species from accessing their spawning grounds, lowering population viability. But is removing them completely danger-free? (Image Credit: pxhere, CC0)

Anybody who has ever studied freshwater ecosystems will end up having to study dams at some point. And they’ll no doubt learn that dams are the enemy. They fragment ecosystems. They cut fish off from their spawning grounds. They change flow regimes. So it makes sense that the recent trend of dam removal across Europe and the world in general would please ecologists. But there’s a problem with dam removal, and it comes in the form of invasive species.

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