River creeps eat and graves: cows sink through the ground and must be tackled from the water

Alarm in the Westland. The red American crayfish have been torn. “They eat everything,” says ecologist Wilco de Bruijne of the Delfland Water Board. With many millions at the same time, they eat aquatic plants and eggs of fish and amphibians. They dig short courses in mainly steep banks of watercourses, and then they dig up with their scissors. Shifting banks, the biodiversity and quality of the water is falling, even water safety is at stake here and there. “If the grab of the crayfish goes together with muskrats, drought and cattle on a dike, a Veendijk can just shift,” says De Bruijne.

With a weir in a watercourse near the Lier, next to the greenhouses of a paprika farm, a new steel embankment was installed last week, showing that large lobster holes had been created in two places. Through those holes, the water, around the weir, flowed to the lower water. “Then you cannot achieve the desired water level,” says area manager Rob van Zijll.

And to think that the Delfland Water Board has thousands of such weirs. Many threaten to touch the red American crayfish. The exotic aquatic animal causes a lot of damage in particular in the peat meadow in the west of the country. “Where the crayfish appears, no more frogs or toads will be falling within a few years, and the fish stock also falls,” says De Bruijne. Not so strange, for those who consider that every mother lobster carries four hundred to six hundred eggs. “And if you catch a large lobster, the released eggs release and fall into the water bottom, to grow on it.”

In addition, the water quality falls “when the crayfish starts to toss, causing the water to get cloudy and water plants can no longer grow.”

The water in the waterway in the Lier is indeed not clear. “They even dig through the ground cloth,” notes Zijll area manager. The traces of the crayfish are also visible in other places. For example a few kilometers away, in Schipluiden, next to the Van Zijll home. Along a ditch lies a fresh pasture under a completely blue sky, which is crumbling on the edges – the result of lobster battle. The banks of the ditch are full of holes.

Damage is unacceptably large

On Wednesday, the Water Board states in a letter of fire to State Secretary Jean Rummenie (Agriculture, Fisheries and Nature, BBB) that the Cabinet as the responsible government must start with ‘far -reaching measures’ to combat the crayfish. It must reimburse tens of millions of euros that water managers have now made to combat the ‘unacceptable large’ damage, and it must reimburse the costs that water managers will incur in the coming years to prevent further damage.

The Delfland Water Board has been attempting for years to come ‘in conversation’ with the ministry, but without result, the water manager writes. As a ‘only management measure’, the Ministry made lobster prescription by professional fishing with selective catches possible. “This management measure has not been effective in any way.”

State Secretary Rummenie “endorses the urgency that the water boards feel,” his ministry says in a response. “There are far too many crayfish in our waters.”

‘Ministry has no vision’

The population of American crayfish has been in Delfland since 2010 “explosively increased and is only in danger of getting bigger,” writes the board of the Water Board. One of the drivers of the Water Council, Stijn van Boxmeer, says: “In conversations with the Ministry, we are always told that professional fishermen can catch the river crayons. But it is not about who she can catch, but that they are being caught. That doesn’t happen. We have the lobsters, with an exemption from the ministry, catching in places where we have installed water nature and eat everything away. That will cost us thirteen million euros in the coming year alone. While that is the task of the central government. And he has no vision on how we can achieve a balance on what an acceptable number would be. “

The central government has the task of combating the wool crab and crayfish. The water boards must take care of the muskrat and beaver rat, and the provinces have the task of combating the other “invasive exotics” on the European Union list, Van Boxmeer explains. “We are not the only ones who suffer from the crayfish. Also think of municipalities such as The Hague. ” According to the Ministry, “structurally” lobsters will soon be able to blame water boards. And Rummenie is working on an “attack plan invasive exotics” that he hopes to present in a few months.

Steep banks, silly slope

The costs of restoring damaged weirs and flood defenses can be calculated well, says the Delfland Water Board. More difficult to estimate is the “very expensive” recovery of ecological damage, the catching away of the lobsters and the damage for farmers. Van Boxmeer: ​​“Weilanden sinks along waterways. And cows sink through the bank, get into the water and have to be tackled again. “

In addition to the leaving of crayfish, replacing steep banks with a faint slope is a structural solution, according to ecologist Wilco de Bruijne. This concerns sloping slope that is overgrown with reeds and is ‘well rooted’ with aquatic plants such as lilies. De Bruijne: “In silly banks, lobsters cannot dig well. We know from research that around seven times fewer lobsters live in those banks. ” And in the end the lobsters, well hidden today, also get more natural enemies in natural banks. “Like futen. Or the pike. ”

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