Thousands of small fish in a large detention pond in Willband Creek Park in Abbotsford have been found dead, for the second consecutive year, and the cause is proving to be a mystery for fisheries officials.
The three-spined stickleback – about the size of a sardine – washed up along the shoreline of the pond in the park located at Highway 11 and Bateman Road.
The deaths occurred at the same time – mid-May to early June – that they did in 2013.
Following last year’s reports of the dead fish, ministry of environment officials ruled out obvious possibilities such as contamination.
Further testing of the water temperature, pH levels, conductivity and dissolved oxygen determined that none of those issues was connected to the deaths.
The incident was declared a mystery and chalked up to a one-time incident.
But this year’s reoccurrence has re-ignited the mystery.
Doug Gosling, a member of the Stoney Creek Salmon Stalkers who was involved in pushing for answers in last year’s incident, was initially concerned that a contaminant was responsible for the deaths.
But an advisor with Fisheries and Oceans Canada tested the fish and the water and ruled out any toxic sources, saying the only species dying in the pond are the stickleback, while other fish and wildlife are unaffected.
As in 2013, further testing did not reveal any other sources for the large kill.
However, officials might be getting closer to an answer. Similar stickleback deaths occurred in Washington State in June 2013, when the fish were washing up on Mercer Island beaches.
Fisheries experts there believed the deaths were part of a natural cycle in which the sticklebacks spawn annually and then die off, leaving a mass of dead fish that wash up on the shore.
But fisheries officials doing research on this year’s stickleback deaths in Abbotsford have not been able to find any information that a mass natural die-off is part of their cycle. They are continuing to look into the issue.