Is there a connection between seabirds and reef fish?

Seabirds are essential for maintaining the delicate balance of coastal ecosystems. However, the introduction of invasive species, notably rats, has disrupted this balance, causing a decline in seabird populations globally. This disruption affects not only seabirds but also has cascading effects through trophic levels, altering the nutritional profiles of organisms in both terrestrial and marine environments.

In March 2024, Camilla Labonte, a Masters by Research Student from Lancaster University in the UK, spent several days on Fregate Island collecting samples for her project. Camilla’s study is focused on three inner islands in the Seychelles:

• Félicité, which has always had a rodent presence,
• Fregate, where rats were eradicated in 2000, and
• Cousine, which has never had rats.

By comparing these islands, she aims to understand the impact of restored seabird-mediated nutrient pathways on the nutritional composition of coral reef fish and macroalgae.

Camilla’s research involved a combination of fieldwork and lab analysis. In the field, she used local fish traps baited with seaweed, coconut, or fish, left for 7 hours at depths of 2–5 meters, alongside handline fishing. All caught fish were promptly stored on ice and transported to a temporary lab on Fregate for dissection.

Once in the lab, each fish was meticulously identified, photographed, weighed, and sized. Muscle tissue was carefully extracted, cleaned, dried, and transported to the Seychelles Fishing Authority (SFA) labs on Mahe island to be grounded to a 5mm particle size. Camilla plans to conduct further analysis on these ground samples back at the university lab. Additionally, macroalgae were sampled at depths of approximately 1 to 2 meters and 100 meters from shore by free diving, while guano was collected by hand only on Fregate Island, as close to the shore as possible.

Upon her return to the university, Camilla will conduct a deeper analysis of all collected samples to analyze their mineral composition and stable isotope levels. Camilla hopes to shed light on the importance of rat eradication in restoring nutrient pathways and safeguarding the nutritional value of nearshore artisanal reef fisheries.

Our conservation team actively participated in the fieldwork to assist Camilla, and we cannot wait to see the results of her project.