Jena Edwards

PhD student, Jena Edwards, has been studying the movement ecology of marine fishes at the Royal Netherlands Institute for Sea Research in North Holland since 2020. Originally from Canada, she developed an interest in aquatic animal tracking while interning with OTN during her marine biology program at Dalhousie University. In this interview, we discuss the use of acoustic and archival tags to track migratory fish in the shallow waters of the Dutch Wadden Sea, as well as the benefits of collaborative telemetry networks.

What questions are you trying to answer with your current research? 

The Dutch Wadden Sea, a UNESCO World Heritage Site, is facing local declines in fish populations due to unknown causes. The current lack of knowledge about fish behaviour, migration patterns and habitat use are hindering the development of targeted management efforts. My research aims to use movement ecology to address these knowledge gaps and determine the importance of the Wadden Sea in the life cycles of large migratory fishes. Through acoustic and archival telemetry, I hope to understand migratory connections and the environmental factors driving seasonality and habitat use in this important intertidal region.

Why is this research important? 

In the Wadden Sea, thicklip grey mullet—previously targeted by commercial fishers—have experienced significant decline and little is known about their seasonal occurrence, movement patterns and destinations outside coastal waters. In contrast, European seabass, a warm-water species once considered a seasonal resident, now thrives in the Wadden Sea, presumably due to local water temperatures increasing, but there is limited knowledge about their migration patterns and behaviour. By tracking individuals from both species over multiple years, we can improve our understanding of the role of the Wadden Sea in individual life histories and clarify the importance of local management actions for broader population stability.   

Describe the research methods for your project.

We use acoustic telemetry to monitor the timing of fish arrival and departure in the western Dutch Wadden Sea. Since the Wadden Sea is used seasonally by many migratory fishes, it is important to determine where fish go when they leave our array area. To do this, we rely on collaborations with international members of the European Tracking Network (ETN) that allow us to continue collecting acoustic detections of fish that pass by arrays in the southern North Sea and English Channel. Another method—archival telemetry—is used to monitor fish beyond the research of acoustic receivers. By recording ambient temperature and pressure experienced by the tagged fish, these devices allow us to model their probable movement trajectories.  

What is the most significant finding to date?

Preliminary data analysis and field observations have provided valuable insights into the behaviours of the study species. Surprisingly, large adult seabass were found not only in the deeper gullies between mudflats, but in shallow waters above mudflats, suggesting opportunistic movement during high tides to expand their foraging habitat. Stomach content analysis of seabass revealed a diverse diet, with a notable abundance of brown shrimp. This finding has prompted further investigation into whether the distribution and abundance of brown shrimp influence the movement and habitat use of tagged individuals.  

How does OTN support your project?

Organizations such as OTN and ETN play a vital role in fostering collaboration, openness, and data sharing among marine researchers. In the field of aquatic telemetry, individual research groups typically establish their own acoustic receiver arrays for studying specific target species. By joining a shared detection data community, however, researchers can link these arrays into a larger acoustic receiver network, enabling the monitoring of individual fish across regional and international scales. This collaborative approach improves data collection and facilitates the exchange of ideas for a more comprehensive understanding of migratory species’ behaviour.