A number of dead fish have been discovered in Lost Lagoon in Vancouver’s Stanley Park over the past few days, prompting an investigation by the Stanley Park Ecology Society.
Conservation technician Olga Lansdorp told CTV News that they first heard about the fish on Saturday.
“As far as I know, it is the common carp that is affected by this death,” she said, guessing that the number affected would probably be in the dozens. “My first impression is that they look like dull fish. Looks like they do not really have much fight left in them. ”
Photos and video sent to CTV News by people in the park showed fish floating on the surface of the water in various areas. The community also shared video showing fish gathered together just below the surface of the lagoon.
Lansdorp said while there is still mystery about what exactly happened, some possible theories may involve last Friday’s heavy rain.
“There was about 51 millimeters of rain on Friday last week, which is a significant rainfall for September in one day,” she said.
Lansdorp said in late summer, waste decomposed at the bottom of ponds leads to a drop in oxygen content.
“With heavy rain, everything is mixed, and then water with low oxygen content is mixed into the rest of the body of water, and what you find is that there is a certain tolerance that fish have for oxygen levels,” she said. “There are also known to be heavy metals in the sediment at the bottom of Lost Lagoon, so the heavy rain may have stirred the heavy metals up.”
The heavy metals would be a concern, for it could end up traveling up the food chain.
“It’s not just the fish that use the water mass, it’s also lots of invertebrates that are then eaten by birds, which are eaten by birds of prey,” she said. “I’ve seen otters eating carp, and I’ve also heard of eagles catching carp.”
Lansdorp said the community is testing the water quality and will investigate whether there are other cases like this in the lagoon’s history or elsewhere.
She also pointed out that the carp are actually an invasive fish and are not native to the area.
“The lost lagoon actually used to be a tidal mud surface, and with the construction of the highway in the early 1900s, around 1916, that part was blocked off and it turned into a freshwater water,” she said. “Ecologically, it’s a kind of new ecosystem.”