As an ex-angler, who used to enjoy sitting on a river bank dangling a maggot into the water to see what I could catch, I take a passing interest in fishy stories.
My friend Pete, who lives in Liverpool, told us about the dead fish that they had found in Walton Hall Park lake. Why the fish had died was a bit of a mystery. The most likely cause was thought to be a change in atmospheric conditions which had lead to a growth in oxygen sapping organisms.
At the time, I told Pete that finding dead fish in the river Segura was a regular occurrence, especially in summer when water levels are low and there is insufficient flow to oxygenate the water. There can also be problems caused by pesticides leaching into the water from nearby agricultural land.
True to form, I now read that over a tonne of dead fish have been discovered floating in the River Segura in Guardamar by members of the Friends of the Wetlands in Southern Alicante (AHSA) who were monitoring birds in the early hours of the morning. Around the same time last year there was a similar occurrence, which was caused by the spillage of pesticides, according to AHSA.
“The CHS (Hydrographic Confederation of Segura) should act more forcefully to prevent a recurrence of events like this that endangers the fragile recovery of the mistreated River Segura,” said Sergio Arroyo, AHSA president. The mullet and carp fish bodies have been removed and research is underway to determine the cause of their deaths.
The CHS are considering two main hypothesis: one is that the high temperatures in recent days “decreased the oxygen in the water causing death by asphyxiation.” The second is that it may be due to the agricultural use of compost or some kind of disinfectant.
What happens is that, due to the drainage of irrigated land, the levels of toxins in the water can become concentrated when there is little flow in the river causing mortality of the fish.