Master's student Naomi handling a puffed up pufferfish!How do fish handle stress? With the rise of human and climate related stressors, researchers are actively exploring how fish react to these conditions. Naomi Pleizier, a MSc. student from the Cooke Lab at Carleton University, Ottawa, Canada, ventured to CEI to discover how short-term stress affects the long-term fitness of one of the mangrove ecosystem’s most charming residents, the checkered puffer fish (Sphoeroides testudineus).

A pufferfish receiving a cortisol treatment

Adapted to the dynamic mangrove habitat, checkered puffers are well equipped to handle the fluctuating environment and the threat of predators. This species has an amazing tolerance of a range of salinities and temperatures. Predators must beware of these harmless looking little fish; not only do they puff to an incredible size in response to threats; they are also rendered toxic by the plankton living in their tissues. Not only that, but they have a mean bite, as study volunteers can attest to!

The puffers’ active responses to predators make them an excellent candidate for the study of stress. The research team collected puffers from Paige Creek and transported them to the CEI lab for treatment. One group of fish was injected with a stress hormone, cortisol, and all fish were tagged before returning them to the creek. In six months, the team will return to the creek to recapture the tagged fish. In the lab, the puffers will be given a series of tests to see how the stress hormone affected their health. The researchers will measure how chubby or thin the fish are, examine the health of their immune system, and challenge the fish  to a range of tests, such as bite force, puffing amplitude and duration, boldness vs. hiding, and more. For now, the team must wait and look forward to meeting their feisty little subjects again soon!