What can fish tell us about our changing world?

If you’re like most people, you don’t spend a lot of time wondering what goes on in the mind of a fish. But these four researchers in Concordia’s Department of Biology are passionately engaged with the topic and its broader implications for the planet.

Dylan Fraser: ‘How do fish adapt to human-induced environmental change?’

As a teenager, fishing gave me a focus. I became passionate about fish and aquatic environments. As I got older, I saw how human activities were impacting the wild spaces I cherished so much, and wanted to do something for the fish that had given so much to me.

My students and I study fish in Newfoundland, northern Quebec, the northeastern US and several national parks in western Canada. We have learned that fish are incredibly resilient animals in terms of the kinds of environmental change they can handle, how plastic they are to dealing with change and how much genetic diversity they can retain even when their populations are small.

But fish are still declining or disappearing in many places. My doctoral student, Elizabeth Lawrence, and I are currently mapping the extent of population diversity in fish across the Americas to assist with improved conservation strategies for them. 

Canada is truly blessed to have so many lakes and rivers full of freshwater fish. We need to find ways to take better care of many of them, though. Fish teach us that life can be resilient and find a way to carry on, provided the rate of environmental change humans impose is not too great.

Grant Brown: how do prey fish learn to survive?

I have always been intrigued by the complexity of behavioural decisions animals are forced to make in order to avoid detection and capture by predators while still finding enough time and energy to find food, court mates and defend resources. Balancing these behavioural decisions assumes honest and reliable information about local conditions. However, variability in local habitats makes it increasingly difficult for animals to have this type of information.

Uncertainty regarding, for example, local foraging opportunity and predation risks are expected to dramatically increase the costs of “making a bad decision.” My graduate students and I use a combination of laboratory and field experiments to test the role of ecological uncertainty on the behavioural decision-making processes of prey populations.

Recently, we have shown that prey exposed to high and variable (uncertain) predation risks, even for a few days, will exhibit an increased avoidance (neophobia) of all novel stimuli. This allows prey time to fine-tune their behavioural decision-making through direct experience. I think the most surprising thing that we’ve shown is the prey fish’s highly sophisticated ability to learn.  

We are currently exploring the possibility of inducing neophobia in hatchery-reared Atlantic salmon prior to their release into natural waterways as a tool to enhance post-stocking survival. We have shown that relatively short periods of elevated predation risk results in dramatic changes in how fish brains grow. The next step is to link these changes to the behaviour of prey.

James Grant: How can we restore fish populations in the Anthropocene?

I have been interested in observing fish behaviour in the wild ever since my Dad took me to see the white sucker spawning run in our local stream — it was spectacular. Later I had a fantastic mentor who supervised my undergraduate Honours thesis and started me on the more formal path of fish research.

My students and I are embarking on exciting new field experiments on brook trout population dynamics at Cape Race, Newfoundland and on the restoration of Atlantic salmon in Lake Champlain tributaries. My personal research will attempt to synthesize data in the literature to answer broad questions about fish ecology and conservation.

Our most recent synthesis showed that most dams in Canada do not have fish passage facilities and those that do are only about 50 per cent effective at passing fish upstream. Consequently, dams divide fish populations into smaller units, making them more isolated and susceptible to local extinction.

If you are lucky enough to study vertebrates in the wild, you observe sad declines in these populations over your career. Atlantic salmon are extinct in Lakes Ontario and Champlain and are threatened in the Maritimes. Because of these declines, vertebrate ecologists always end up doing conservation work at some point in their career. 

Pedro Peres-Neto: ‘Why are fish species where they are?’

Most of my research has been dedicated to stream fishes and how lakes and streams differ as habitats for fish. Streams are highly dynamic, and temporal changes in fish environments can take place within hours, days or years. This generates important spatial and temporal variation in stream habitat for fish, and creates challenges for their growth, reproduction and movement. In contrast, lakes provide more stable habitats for fish.  

For my research team, the big question is, “Why are fish species where they are?” To answer this, our research mixes theoretical, laboratory and field approaches.  Our ultimate goal is to understand how species characteristics (e.g., morphology, dispersal capacity, life history, behaviour, physiology), habitat structure and connectivity as well as species interactions influence the types of fish that are found in different stream and lake habitats.

Our research determined for the first time that the different microhabitats in streams (riffles, pools and runs) can induce fish to have very different shapes across many species. This is despite the fact that the dynamic and often unpredictable nature of stream systems would predict that fish should actually be able to occupy any habitat type.

The next step is to understand how different factors at different spatial scales affect fish growth and how they interact within and across habitats via movement at small and large distances. These scales range from small streams and lakes to provinces and continents and across the globe.

Find out more about Concordia's Department of Biology.