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Redfish feeding under a student’s microscope

Îles de la Madeleine

A study confirms that the diet of redfish has varied over the decades, more specifically between its near disappearance in the 1990s and its recent comeback in the Gulf of St. Lawrence.

This is the subject of the doctoral thesis of Sarah Brown-Vuillemin, a student in oceanography at the Institut des sciences de la mer de Rimouski (ISMER-UQAR), which has been published in a scientific journal.

She says she examined and compared the stomach contents of nearly 4,000 fish caught during Fisheries and Oceans Canada missions from 1993 to 1999 and from 2015 to 2019.

She notes a change in the diet of juvenile rockfish between the two reference periods.

As they mature, rockfish become piscivorous, feeding on things like capelin or shrimp, with shrimp remaining their prey of choice regardless of the time frame, she notes.

Sarah Brown-Vuillemin has also observed a tendency for cannibalism among larger fish.

She will continue her research on redfish feeding, this time using two techniques to identify what redfish collected in 2017 by the DFO ate: fatty acid analysis and DNA testing of stomach contents.

According to the department’s 2019 data, the biomass of Atlantic and Acadian redfish is at least 4.3 million tons.

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