For the past few days, images of dead carp floating belly up on the shores of Stanley Park’s Lost Lagoon have surfaced on social media prompting many to wonder what's going on.
Olga Lansdorp, a conservation technician with the Stanley Park Ecology Society (SPES), says the short answer is there is no definitive answer, just a few theories. The theories, Lansdorp posits, revolve around the 51 millimetres of rain that was dumped on the lagoon last week.
“There is a precedent for heavy rain like that in late summer to cause all of the water in the pond to mix,” Lansdorp explains. “At that time of year, there's often a zone, an anoxic or very low oxygen zone, in the lower layers of the body of water. So if those get mixed in with the upper layers, they can cause anoxia, or low oxygen levels to persist throughout the body of water."
Lansdorp adds the rain may have also stirred up heavy metals in the sediment which could also prove deadly to the resident carp.
To get to the bottom of this fishy mystery, the SPES and the Vancouver Park Board are working together on an investigation that will involve conducting necropsies of the deceased carp.
Lansdorp did not mention when the results of said necropsies would be available.
The carp die-off might not be all that bad for the lagoon itself though. In a 2011 report from the SPES, the invasive carp was listed as one of the factors affecting the pond's water quality. At the time it was suggested that fishing for the carp be encouraged while banning their re-release into the lagoon, even going so far as to drain the lake outside of breeding season to avoid eggs remaining in the lake floor.