Master's by Research student Rebekah Trehern has been working at the Cape Eleuthera Institute (CEI) for the past 5 months conducting research for her thesis project. Rebekah is a graduate student at the University of Exeter, under the supervision of Dr Lucy Hawkes (UoE) and Dr Travis Van Leeuwen (CEI). The focus of Rebekah’s study is investigating the bioenergetic costs of lowered salinity levels on the invasive red lionfish (Pterois volitans).

Red lionfish are an invasive species in The Bahamas and were first recorded in the area in 2005. Since then, many scientists have conducted research on this species at CEI, monitoring them in captivity and in the wild to track their movement and observe their foraging behaviour (the published studies can be found on the CEI website). In recent years, observations have documented an increasing presence of lionfish in mangrove ecosystems, known to be valuable nursery habitat for many juvenile fish and not previously thought to be an ecosystem likely to be inhabited by lionfish. Rebekah’s captive study aims to determine the invasive potential of lionfish by monitoring growth rate and metabolism in a variety of different salinities.

A captive lionfish is isolated in a white tote to ensure it is fed the correct amount of fish.

A captive lionfish is isolated in a white tote to ensure it is fed the correct amount of fish.

Over the past 3 months, we have reared 66 lionfish in the tanks at the CEI wet lab. At the beginning of the year, Rebekah and several CEI interns collected live lionfish from various patch reefs off the coast of the CEI campus. The lionfish were then divided between different tanks in the wet lab which were kept at three different levels of salinity. Natural seawater was used as a control, a lower salinity of 20 parts per thousand (ppt) simulated the salinity levels of mangrove ecosystems and 10ppt produced conditions at the lowest known salinity that lionfish have been known to survive for significant periods of time. Throughout the duration of these salinity treatments, Rebekah conducted various experiments including maximum growth and metabolic profiling using respirometry equipment. She hopes her results will show how lionfish compensate for the cost of living in low salinity habitats, when considering their metabolic rates, feeding activity, digestion and growth.

Rebekah catches a lionfish to measure it and monitor its growth rate.

Rebekah catches a lionfish to measure it and monitor its growth rate.

During her time at CEI, Rebekah has also being co-advising an Island School research class. Her class has been investigating how the presence of lionfish affects the behaviour of native species in a mangrove habitat. They set up a captive study in the wetlab, using a mangrove root to simulate the natural creek environment. They videoed the interactions between lionfish and schoolmaster snapper (Lutjanus apodusand) and identified any changes in how the snapper sheltered in the mangrove root. Every week, The Island School students helped Becki with her with field work, including setting up the trials in the campus mesocosm and assisting with video analysis. The students also produced an exceptional presentation about their project, explaining the methods they used and the results obtained, which they proudly presented for their parents just a few weekends ago. Rebekah is now expanding her project further and conducting the same experiment as with the students, but fully simulating a mangrove environment by using water with a salinity of 10ppt.

Island School students collect schoolmaster snappers from a local creek.

Island School students collect schoolmaster snappers from a local creek.

Preliminary analysis of the captive lionfish growth data indicates that the fish kept in 10ppt salinity grew significantly less than those in the higher salinity (20ppt) and standard sea water treatments. This could suggest that in a mangrove ecosystem, lionfish will grow at a much slower rate than those individuals who inhabit reefs. The results of the respirometry experiments show that the aerobic scope maximum of lionfish were significantly lowered in 10ppt water, suggesting that the fish are partitioning energy differently to survive in low salinity environments. Finally, the preliminary results of the behavioural studies with The Island School students, suggests that schoolmaster snapper use the shelter of a mangrove root significantly less when in the presence of the lionfish.

Rebekah is excited to return to Exeter to further discuss these findings with her supervisor Dr Lucy Hawkes, where she will use the data collected at CEI to produce a thesis and publish her findings in a high quality peer-reviewed science journal.