Visitors to Sardis Park were shocked Thursday morning to see hundreds of dead fish on the banks of the pond.
City of Chilliwack staff were dispatched to the park after the phones started ringing at city hall.
Early findings from the investigation showed that low levels of dissolved oxygen were to blame for the die-off of between 500 and 700 fish, which were identified as large-scale suckers and sculpin.
The water-testing and cleanup were conducted with the assistance of the City of Chilliwack’s senior environmental watercourse specialist.
“The testing revealed that the dissolved oxygen levels were not sufficient to support fish life,” according to the city press release. There were no trout or salmonids amidst the suckers and sculpin.
It turns out that a minimum of two milligrams per liter is required to sustain the fish, and the dissolved oxygen levels in the middle of the pond were an average of 1.6 mg per litre.
“In order to increase dissolved oxygen levels in the pond, operations staff filled the pond with dechlorinated water and monitored the inflow at the pond to confirm that no chlorine residual was present.”
The remaining fish quickly congregated around the inflow stream and appeared to rally.
“Staff will continue flushing until the dissolved oxygen levels improve.”
The long dry summer and fall conditions may have played a significant role in the decreased oxygen levels, say officials.
With the water level in the pond so low, and with little to no outflow movement, the water may have become stagnant, causing the deterioration in the dissolved oxygen levels.
“The City of Chilliwack has never experienced fish mortality like this at Sardis Pond and will continue to monitor the situation in the days to come,” said the release.
Officials expect the fish to repopulate themselves, and will not be replacing them.