WWF-Canada Blog:
Freshwater


Reflecting on the Health of Canada’s Waters: Fish

At WWF-Canada, we’re one quarter of the way to reaching our goal of assessing the health of all water in Canada by 2017. We’re taking the temperature of Canada’s watersheds based on the condition of their water flow, water quality, fish and bugs. July has been Water and People Month at WWF, and we’ve shared blogs about the overall trends we’ve been seeing in water health, and water flow. Today we look at how we can determine river health through its fish.

A Sockeye salmon (Oncorhynchus nerka), part of the annual migration, in the Adams River, British Columbia, Canada. © Garth Lenz / WWF-Canada

A Sockeye salmon (Oncorhynchus nerka), part of the annual migration, in the Adams River, British Columbia, Canada. © Garth Lenz / WWF-Canada

It’s hard to picture healthy water without fish. As top level predators, they’re integral to the well-being of the entire food web in freshwater ecosystems. So what can fish tell us about water health?  Across Canada, the most consistently available information we have about fish are lists indicating if specific fish species are present or absent. We look at these lists over time to determine if there has been a decline in native fish species. If the number of native fish in a river are declining, that’s a clear sign of the declines in the overall health of the fish community.

It’s good news that in the 25 per cent of Canadian freshwater we’ve assessed, native fish are still present. While some watersheds lacked sufficient data, most of the watersheds we examined received a good score, meaning we have not experienced a loss in native fish species.

FHA_Fish_Scores_basins_06052014There are some caveats to this good news though. First of all, we only look at whether a species like salmon, for example, are present or absent from the river; not whether the number of salmon in the river has declined.  Secondly, the monitoring data available tends to target recreational or commercial species, rather than species that are important to the ecosystem. Finally, many recreational and commercial species are stocked in the river so we can’t know whether these populations are naturally healthy or if they are present because people have put them there.  We’re hoping to address some of these challenges in the future but in the meantime, we’re happy to see that the number of native fish populations is not declining.

A methodology is only as good as the data available. That’s why open-access data like the British Columbia, Alberta, and Ontario fish observation databases are so important to us and other water organizations. By sharing data, together we can paint a picture of the health of fish populations across Canada.

Stay tuned for more information about fish metrics as we work towards evaluating all water in Canada by our country’s 150th birthday in 2017!