Morgan Piczak

Morgan Piczak is a Liber Ero and NSERC postdoctoral fellow at Dalhousie University. In this interview, we explore the use of acoustic tracking to study the spawning and migration routes of Atlantic mackerel. 

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

Atlantic mackerel were once considered abundant, but they experienced an unexpected collapse due to overfishing, leading to the closure of the commercial fishery in 2022. This was alarming because Atlantic mackerel play a crucial role in marine ecosystems, linking zooplankton at the base of the food web with top predators like marine mammals, birds and larger fish. Our study seeks to address several key questions:

• What are the migration routes and spawning sites of Atlantic mackerel?
• How do temperature fluctuations influence their location and depth?
• How can we use this information to refine management strategies, such as implementing seasonal closures?

Additionally, we aim to estimate mortality rates by tracking the survival of tagged individuals to provide a more accurate assessment of the spawning stock biomass—defined as the total weight of spawning individuals. 

What was the biggest challenge you faced during this project?  

The most significant challenge was developing a new tagging method suited to the nature of Atlantic mackerel. These fish have sensitive scales and need to continuously swim to breathe. Traditional chemical anesthesia, which slows recovery, was not ideal. Instead, we used electro anesthesia, allowing fish to recover almost immediately after the procedure. This rapid recovery is critical in minimizing predation risk. I had previously used this method during my PhD and believed that it would be perfect for this study. We began by testing this method on mackerel in captivity in Dalhousie’s Aquatron facilities. Once we transitioned to fieldwork, we had to adapt our techniques for the different conditions on a boat. Our team, consisting of five members, made sure to prioritize animal welfare. We focused on minimizing handling time and used wet nitrile gloves to protect the fish’s sensitive scales. We successfully tagged about 200 fish within three days, and while we are still assessing survival rates, the fish appeared to recover well and swim away.

Morgan (right) tagging an Atlantic mackerel using the new tagging method of electro anesthesia gloves (left).

What are the future applications of this study?  

We are currently working with a Fisheries and Oceans Canada (DFO) scientist who is responsible for estimating the spawning stock biomass of Atlantic mackerel. We wanted to work with decision makers and environmental managers to make sure that the research we are doing is actionable. Historically, it was believed that Atlantic mackerel spawn primarily in the southern Gulf of St. Lawrence, though other spawning sites might exist. Identifying additional spawning areas could lead to more accurate estimates of egg production and spawning stock biomass, informing sustainable catch limits and the future management of this fishery. Atlantic mackerel studies have also been complicated by a lack of tracking infrastructure in the United States. There are two populations of Atlantic mackerel, the northern contingent which we tagged, and the southern contingent—which spawn in the United States. Both groups come together in the winter, but we do not understand their interactions. It would be great to get even more coverage in this area, with more receivers and tags to help understand the mixing of these contingents. 

How does OTN support your project? 

This project would not have been possible without the infrastructure that is maintained by OTN. Their support enabled us to test new tagging methods in Dalhousie’s Aquatron facilities and provided essential receiver lines for tracking mackerel in the wild. OTN’s receiver arrays have been crucial in determining how many tagged fish pass through key points, such as the Halifax Line, and for identifying their migration routes. Their contributions to data collection and collaborative research have been instrumental in our efforts to understand and manage Atlantic mackerel populations effectively.