New paper - tracking fish in low-oxygen waters

In a new review paper lead by Dr. Steven J. Cooke at Carleton University, we explore how electronic tags and tracking technologies are changing our understanding of how fish respond to hypoxia (low oxygen conditions) in the wild.

Low oxygen is becoming an increasing challenge in many aquatic ecosystems, such as Norwegian fjords, due to nutrient runoff, climate change, and changing environmental conditions. While laboratory studies have revealed a great deal about how fish respond physiologically to hypoxia, it has been much harder to understand what individual fish actually do when they encounter low-oxygen water in nature.

By using electronic tags equipped with sensors, researchers can now follow fish movements, behavior, depth use, activity, and even aspects of physiology in real time. These tools are revealing that fish responses to hypoxia are often far more complex than previously thought.

Illustration from Cooke et al. 2026. Illustration by Rush Dhillon.

Tracking studies have shown that low oxygen can compress available habitat, forcing fish into smaller areas with suitable conditions. Tags have also uncovered hidden mortality, unexpected movement patterns, and trade-offs between avoiding hypoxia and accessing food, shelter, or optimal temperatures.

The review highlights how electronic tagging has helped researchers understand decades-old hypoxia challenges in systems such as Lake Erie, while also demonstrating the value of combining field tracking with laboratory studies.

As tagging technologies continue to improve, we expect even more discoveries about how fish cope with environmental stressors in a rapidly changing world. These insights will be critical for managing and mitigating the impacts of hypoxia on fish populations and aquatic ecosystems.

You can read the paper here!