Horse Chestnut
Horse chestnut and to the right Sweet chestnut
Soapwort
It has been a mystery for years in the town Kolding in East Jutland. The environment technicians of the municipality wondered, why dead fish were found each autumn in a brook near town, but a common citizen drew the attention to that the death of the fish always happens, when the chetnut-fruits fall down. This indicates that it is that simple as that: chestnut trees are the reason, why about 300 fish in Skanderup Brook died in the week-end.
Close to the brook is a chestnut-avenue - it is the horse chestnut, Aesculus hippocastanum, which is related to soapwort. They both contain saponin, which is poisonous to fish.
The sweet chestnut or marron, Castanea sativa is from another family ( fagaceae).
Probably it is caused by that the chestnuts are crushed by cars driving by, and a heavy shower means that the poisonous stuff from the crushed fruits is flushed down into the brook with the rain water, says the environment technician. After having examined the subject, he found out that North American Native tribes have used the saponin to catch fish.
But the trees will probably not be cut down. They still work on how to solve the problem next year in the environment section in Kolding.
North America:
Fish poisoned by saponin become stupefied and float to the surface where they can easily be collected. Indigenous tribes across the Americas used saponin poisons from many plants.
Survival Skills of the North American Indians.
photo horse chestnut & soapwort: grethe bachmann /photo sweet chestnut: vestrehus.dk)
