How to save an endangered fish

Green transition 21 November 2017 Peter Bønløkke Adamsen

Until a few years ago the production at a lot of Danish fish farms was damaging the populations of wild fish in the creeks. A large-scale, EU-financed rescue plan has improved the conditions but there are still complex challenges to solve.

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The calculation was unusual and quite difficult too: hydraulic experts had to find the optimal meandering for the creek – but with a minimum amount of soil. 

“Soil is very expensive to move, so we basically had to use what was already here,” explains Ebbe Høy, the project manager from Vejen Municipality. 

Vejen is one of the Danish municipalities obliged to protect the houting, a small, red-listed salmonid. The houting is the rarest freshwater fish in Denmark and, in fact, among the rarest in Northern Europe. The fish once thrived in most of southern Jutland and northern Germany, but fish farms and other industries put weirs and dams in the creeks as part of optimising their production. 

This practice was far from environmentally responsible – and did particular harm to the houting, which does not swim as well as salmon or trout. 

“The houting had no chance of ascending the creek and spawning on a stretch like this,” says Ebbe Høy, pointing to the small creek, part of the Sneum River system in Glejbjerg, a village west of the town of Vejen. 

The local fish farmer had changed the once meandering creek into a straight canal and, even more importantly, installed a weir that was impassable for fish and other aquatic fauna. As a result, houting and other salmonid species could not reach their spawning grounds upstream from the weir. 

Precise calculations

The fish farm here in Glejbjerg is now closed, as are the vast majority of fish farms in this and other creeks in southern Jutland. In 1980 there were 29 in the Sneum River system; now there are only three. This is chiefly due to a large-scale rescue plan for the houting, a plan running for almost 20 years and financed in great part by the EU, because the houting is a high-priority species. 

The plan has been a success. Houting have been breeding further downstream for a couple of years, and this spring anglers have already reported seeing salmon and trout spawns upstream from Glejbjerg. 

However, living conditions are not yet good enough for the houting, which is why Vejen Municipality needed experts to optimise the meandering of the creek. 

“Ramboll did the calculations and determined that we could manage the meandering with the soil we already have here,” Ebbe Høy says, pointing to the muddy banks of the creek. “This way the meandering makes both environmental and economic sense.” 

Water from pumps 

The challenges in the Sneum River system are not over, though. Another tributary at Holsted still has an active fish farm, and Vejen Municipality and Ramboll are working on a solution that allows the fish farm to continue production – although with due consideration for the natural environment. 

The fish farm requires a large amount of water, but the stream must also be more stable and houtingfriendly. One of the solutions being considered is the use of groundwater pumps. 

Ramboll is also in the process of removing obstacles in Ansager, a side creek of the Varde River system and the northernmost habitat of the houting. 

“There are still essential projects that have to be completed before the houting can enjoy good living conditions again in all of its habitats,” says Peter Bønløkke, Market Manager at Ramboll.

Written by Michael Rothenborg.