Ava Sergio

Ava Sergio is a master’s student at Dalhousie University, investigating the critically endangered Atlantic whitefish. In this interview, we discuss her research into the species’ behaviour, potential spawning sites, and interactions with invasive predators.

What research questions are you trying to answer with this project?

Atlantic whitefish are genetically, culturally, and ecologically unique. They’re endemic to Nova Scotia, meaning that they’re found nowhere else in the world. They’re also an ancient species that lived here since before the last Ice Age—outliving both the dodo bird and the woolly mammoth. Atlantic whitefish are listed as critically endangered on the IUCN Red List and have been listed as endangered under Canada’s Species at Risk Act (SARA) since it came into force in 2003. The species is so rare and poorly understood that fundamental questions about the ecology of Atlantic whitefish are limiting the effective implementation of the SARA recovery plan.

Our research questions were created to target the current knowledge gaps:

• What are the fine scale seasonal movements of Atlantic whitefish in their critical habitat?
• Where are potential spawning sites for Atlantic whitefish within Milipsigate Lake, N.S.?
• Do Atlantic whitefish exhibit anadromy—born in fresh water, mature in the ocean, and return to fresh water to spawn?
• What is the seasonal movement ecology of invasive predators—chain pickerel and smallmouth bass—in Milipsigate Lake and how might it impact Atlantic whitefish recovery?

What were the main causes of decline of the Atlantic whitefish?

There are two main factors that contributed to the decline of Atlantic whitefish. The first was the construction of numerous dams throughout the freshwater systems of Nova Scotia in the late 1800s and early 1900s, particularly near Bridgewater. Atlantic whitefish are migratory, moving between freshwater and saltwater during different stages of their life cycle. The dams blocked these migration routes, preventing the fish from traveling between their spawning grounds in freshwater and their feeding grounds at sea. This disruption significantly contributed to their population decline, as they could no longer complete their natural life cycle.

The second major factor was the introduction of invasive smallmouth bass and chain pickerel to Nova Scotia. Both species prey on Atlantic whitefish, with chain pickerel being particularly aggressive. In addition to predation, these invasive species outcompete Atlantic whitefish for vital resources, further threatening their survival.

Describe your research methods:

To address our research questions, we used a combination of acoustic telemetry equipment to create an expansive array in the Petite Rivière watershed. The array starts in Milipsigate Lake, N.S., and continues through other interconnected lakes that feed into the Petite Rivière before leading to Green Bay—an estuary connecting the freshwater habitats to the Northwest Atlantic Ocean. All the Atlantic whitefish that were tagged for this project were captively bred in Dalhousie University’s Aquatron facilities, as there are so few left in the wild. So far, we’ve tagged over 150 individuals and plan to do a final round of tagging and releases this summer. The movements of tagged fish are being recorded by receivers—which we will later offload for data analysis.

What are the future applications of this study?

We are working in conjunction with Fisheries and Oceans Canada to build on their long history of Atlantic whitefish research, and our findings will help fill critical gaps in the current recovery plan for the species. By identifying important spawning sites and understanding the impact of invasive smallmouth bass and chain pickerel, our research will allow conservation managers to make more informed decisions and assist in the effective implementation of the Atlantic whitefish SARA Recovery Strategy. Additionally, the study will provide the most comprehensive opportunity to evaluate release strategies for captively-reared individuals, hopefully aiding the ongoing stocking efforts as well. Ultimately, our goal is to provide the scientific data needed to implement effective conservation strategies so that Atlantic whitefish have a higher chance of surviving in the wild.

How is the surrounding community involved in the project?

The community within the Petite Rivière watershed is highly aware and supportive of Atlantic whitefish conservation efforts. Over the years, initiatives have been undertaken to raise awareness, and it’s clear that without the community’s involvement, this work would be much harder to achieve. The people living in the area have a strong connection to the whitefish, and many are proud that they share their backyard with this critically endangered species. Everyone we talk to seems to know about the whitefish and is supportive of the work we’re doing, which isn’t always the case with conservation projects. It’s really encouraging to have such a welcoming and engaged community that respects the rules—whether it’s avoiding fishing in protected areas or releasing any whitefish they might accidentally catch.

How does OTN support your project?

I am conducting this research as part of my master’s degree at Dalhousie University and my supervisor is Dr. Robert Lennox, OTN’s scientific director. Rob played a crucial role in acquiring grant funding for this project from the Canada Nature Fund for Aquatic Species at Risk. OTN loaned numerous VR2AR acoustic release receivers that are currently deployed and collecting data about Atlantic whitefish in the Green Bay estuary. OTN also supports my project by providing data services such as quality control for my metadata and analysis support in study hall. They also gave me a platform to present my research during the poster session at the 2024 OTN Symposium in Halifax, Nova Scotia.