Fish Productivity – explaining environmental issues through the lens of fish
Posted on: March 22, 2021
Haley MacLeod out in the field

Haley is a Ph.D. student from Echo Bay, ON who is working under Dr. Michael Rennie at Lakehead University. She did her undergrad and masters at Trent University where she worked on cancer research. But Haley realized that she wanted to prevent people from getting sick by studying contaminants in the environment. Her interest in environmental toxicology sparked a conversation with Dr. Rennie which led her to where she is now. Haley’s doctoral research focuses on understanding the impact of microplastics of fish productivity and using long-term fish and ecosystem data at the IISD-Experimental Lakes Area (IISD-ELA) to develop new time- and cost- effective methods to monitor freshwater fish health.

Microplastics are a common household name. They’re the tiny pieces of plastics that break down from larger pieces that can be found nearly anywhere on earth. Haley is looking to see how microplastics impact fish productivity. The experiment runs in the fish lab at Lakehead University where Haley has 24 tanks. Fish eggs from the Dorion fish hatchery are exposed to various levels of microplastics that represent current concentrations and concentrations that are expected to be found 50 years from now. The fish will be exposed to three different types of microplastics that mimic the different types of microplastics in the environment to represent how different plastics accumulate within the water column. Each of the plastics have different buoyancies. One of the plastics floats on the surface, one is suspended within the water column and the other plastic sinks to the bottom. She is also exposing the fish to a wide range of sizes to mimic the way plastics accumulate in the environment.

Fertilized fish eggs

People understand the physical ingestion of microplastics and how that can harm fish, but there is a lack of understanding of how the chemicals that are added to plastics influence freshwater ecosystems. Haley is looking at both the physical and chemical impacts that microplastics have on fish productivity. Chemicals such as UV stabilizers, antioxidants, and others such as BPA, but her research focuses on UV stabilizers and antioxidants which are additives that prevent the breakdown and colour leaching in plastics. These chemicals have been deemed as a chemical of emerging concern from Environment Canada. They are finding them in high concentrations in sediments and also aquatic ecosystems. There is a lack of understanding of how these chemicals interact with the environment, but research has shown that these chemicals have the ability to bioaccumulate and have the potential for endocrine-disrupting effects which is concerning. The fish eggs in the tanks are being exposed to microplastics which are leaching chemicals into the water. Haley wants to understand what will happen to the developing eggs as they are exposed to these known endocrine-disrupting compounds that bioaccumulate. The eggs will eventually hatch and start feeding and this will allow her to look at how the chemicals impact development. Once the fish start feeding, Haley will look at how the physical ingestion of microplastics impacts the growth, development, and mortality of the fish. From there she will use recruitment models, which is the number of individuals which successfully make it into a population to see how microplastics will impact productivity over time

Larval fish in the microplastics experiment

Haley expects to see that once the larval fish start to eat, they will interact and ingest plastics that are positively buoyant, and this affects their growth rate. Her study is part of a mesocosm study at the IISD-ELA. Mesocosms are a way to study lakes without exposing the entire lake to see how these mini ecosystems respond to the same plastics in Haley’s tank study. Through her research, she will be able to answer some fundamental questions about microplastic toxicity which is lacking in freshwater ecosystems.

The remainder of Haley’s research is working with long-term data at the IISD-ELA. ELA is a world-renowned research facility located in northwestern Ontario that’s close to Dryden that’s comprised of 58 lakes with long-term data on fish populations, and various metrics within the lakes themselves. It’s one of the only places in the world with such comprehensive long-term freshwater data where you can properly calculate estimates of fish production. At ELA, you can also experimentally manipulate, which offers unique research opportunities.

Haley is using long-term data to study fish productivity which is defined as the amount of tissue elaborated per unit time per unit area. It is a comprehensive metric that incorporates the best fisheries metrics which makes it a sensitive estimate of how fish populations and aquatic ecosystems are doing. It is a metric that has been held on a pedestal in fisheries literature, but there is a lack of information on fish productivity due to time and monetary costs to calculate these estimates. ELA is unique because the datasets are there to calculate estimates to start looking at what environmental variables are driving fish productivity and what variables are correlated with fish production so we can develop new indicators for fish productivity for management and conservation use. The ideal situation will be to have a few different environmental variables that we could go in and easily sample and know that the variables are indicative of fish productivity to say that the fish population is happy or isn’t healthy. Haley is hoping to create a suite of indicators that can determine the health of a fish population and the ecosystem.

Studying freshwater ecosystems and fish is a unique opportunity because it allows researchers to tell the story of climate change or contaminant burden through the lens of fish. Using fish productivity as a metric contextualizes how climate change and pollution are going to impact fishing experiences and food resources for a lot of Canadians. As Canadians we are passionate and culturally linked to fishing and freshwater, so Canadians want to engage in conversations around how trophy size fish are being lost due to climate change, or how microplastics are impacting the survival and growth of their favourite fish. These impacts on fish affect an important cultural pastime and access to food resources, and can spark a change and increased awareness on some of the most pressing issues society is facing.

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