Strange creatures in the bay
Scientists are urging people to stop dumping aquarium and market fish into Hamilton Harbour
HARBOUR
SCIENTISTS say they have been finding some strange new creatures in Hamilton Harbour this summer, suggesting people are dumping aquarium and fish market species into the waters.
“We’ve seen some fish that really should not be there and it’s really a sign of people purposefully and irresponsibly and illegally releasing fish into Hamilton Harbour,” said Becky Cudmore, senior science adviser on aquatic invasive species with Fisheries and Oceans Canada.
Among the findings are four tilapia fish and a type of aquarium catfish. This is on top of an established population of goldfish, the outcome of untold numbers of people emptying their aquarium fish into the bay and Cootes Paradise.
“What we are seeing with goldfish is something we don’t want to see happening with other species,” she said.
She believes the tilapia, a nonnative species originally from the Middle East and Africa, were bought at a fish market and then released into the harbour in a misguided effort to save the fish from being eaten.
“It’s not fair to the fish because they are not meant to be in that water,” said Cudmore. She urged people with unwanted aquarium fish to take the fish to pet rescue centres or back to the store where they bought them.
She expects tilapia in the harbour will die out over the winter because the species prefers tropical environments. But some could survive by using warm water effluent from Hamilton steel mills as an overwintering haven.
Tys Theijsmeijer, the head of natural lands for the Royal Botanical Gardens, says as well as adversely affecting native species, introduced
species can bring new diseases to the ecosystem.
“We tend to find them (aquarium fish) near the easiest places for people to get to, such as Princess Point or Bayfront Park and Lasalle Park,” he said. “They drive up and pitch them in.
“It’s amazing the non-native aquarium things we have found over the years. We’ve had a piranha and plecos that are aquarium fish that are used to pluck the algae off the glass.”
Another distressing finding was an adult Chinese mitten crab that was found at the Cootes Paradise Fishway in 2015.
The live crab was captured at the RBG-operated fishway between Hamilton Harbour and Cootes Paradise, and handed over to Fisheries and Oceans Canada. The fishway is designed to block carp from the ecologically fragile Cootes marsh and allow other native, desirable fish species to pass through.
It’s not clear how the crab got into the harbour, but it is thought that it was bought live at a fish market and released in an attempt to save it. The Canadian Food Inspection Agency does not allow the crab species to be imported out of concern over a parasite it carries that can be harmful to human health.
The fishway — that is also used as a station to monitor fish species populations — has seen a major spike in goldfish populations in recent years. Since 2014, numbers have shot up from in the hundreds to 1,706 that year to a peak of 2,446 the following year. In 2017, the last year numbers are available, workers tracked 1,682 goldfish.
Another non-native species causing concern is the rudd, from Europe and Asia. Fishway found the number of rudd jumped to 44 examples in 2017 compared to only seven the previous year.
“It’s become a discouraging part of the rehabilitation of Cootes. You almost expect to find anything,” said Theijsmeijer.
Cudmore said, “native species are recovering in the harbour from decades of poor water quality and we are doing a great job of cleaning that up and providing nice habitat for them.
“But to add an invasive species to that adds another stressor to an already stressed population that is trying to recover.”
AS WELL AS ADVERSELY AFFECTING NATIVE SPECIES, INTRODUCED SPECIES CAN BRING NEW DISEASES TO THE ECOSYSTEM.