It takes more than adding some fish

Ah, the charismatic megafauna, a curse and a solution. I don’t remember when I first learned this term. I can guarantee it was in an ecology course. Charismatic megafauna are animals, almost always mammals that conservationists think people will care about like bears or caribou. Instead of focusing conservation on improving the entire ecosystem, we focus on making life better for these appealing critters. The belief, so I learned in my undergrad, is that the ecosystem will get protected by default when we try to protect the animal on the postcard. I’m not saying that this has never worked but I would guess that the polar bears starving away on the melting ice aren’t holding out a lot of hope that their prolific use when it comes to climate change communication will suddenly take hold and trigger change. And, even if we figure out how to do so, a breeding and reintroduction program for polar bears isn’t going to save us if those introduced polar bears still can’t find appropriate access to food and shelter.

With a little less fanfare than these large mammals, there have been a lot of reintroduction programs. Some have been successful to at least some degree like the swift fox reintroduction in Canada and the US and the Vancouver Island Marmot. But many fail to establish self-sustaining populations, ie, populations that can breed and support themselves and grow until they are no longer at risk. So, what is the alternative?

A new study by Radinger and colleagues (2023) studied whether modifying the ecosystem in different ways or stocking lakes with fish was more effective for increasing fish populations over time. What’s particularly cool about this study is that the researchers used 20 different lakes and monitored them over a period of six years to figure out which approach worked the best. This is something that is a little easier to study in lakes because the lakes are easier to control than many land based ecosystems.

The researchers had three treatments and then controls that were left as is. The three treatments were fish stocking – adding five fish species, creating shallow water zones, or adding course wood bundles. Fish stocking, which is the dominant approach used by fisheries completely failed in every lake. The fish populations did not increase. The wood bundles were effective in some of the lakes they were added to but not all, indicating that there may be other factors at play as well. On the other hand, creating shallow water zones was universally effective. The shallow water zones are typically used by fish for spawning (reproduction) and the lakes with these created zones saw increases in the number of juvenile fish who can then grow up to reproduce themselves.

The challenge is that this type of ecosystem management is expensive, so there’s a lot of risk in doing something that might not work. The authors highlight that to be effective, user groups need to be involved. They need to have responsibility and be supported in their efforts. I think that this likely expands beyond just freshwater ecosystems. If a user doesn’t know why a particular ecosystem change has been done they might actively ignore or even try to change it back.

Going back to the charismatic megafauna, I’m going to go out on a limb and suggest that getting people to donate to preserving grizzly bear habitat would be an easier sell than asking for donations to create a shallow water zone that isn’t for swimming, in a lake. This means that getting support for improving the ecosystem rather than supporting a single animal may be a challenge. As an educator, I see this as evidence for why we need to teach ecosystems at all levels of school. But I also think this is a good reason for why we need to collaborate with Indigenous groups. They have the living history of what ecosystem features bring what animals. They also have amazing knowledge on how to restore those ecosystem features. It isn’t possible to conduct experiments on all available ecosystems to determine what will be successful. Respecting the knowledge of those who have lived with nature for generations might give us the way forward on this front.