We finished our field course with even more fantastic hands-on experiences, here are our final few days in the Bahamas:
We had the pleasure of being led by Brad Weiler and Drew Hitchner on a Coral reef fish survey, which turned out to be the perfect preparation for our fish identification test towards the end of the field course. All groups were taken to two reefs named “Something to see” and “Bamboo” and were told to swim a transect line of 50m (in fin kick cycles). We identified and tallied up the number of fish species we spotted along the transect. By knowing our distance travelled and the number of individuals of each fish species we saw, we had appropriate metrics to estimate fish abundance. Several fish species were identified including the likes of Sergeant Majors (pictured below), juvenile Beaugregorys and Yellowtail Damselfish. Team Starfish were also treated to a fantastic sighting of a juvenile nurse shark resting underneath a rocky overhang. Upon return to the Island School, we calculated values for species richness (number of different species) and species evenness (number of individuals within each species) for the two reefs surveyed, as well as obtaining a value for Simpsons Diversity Index.
Dr Owen O’Shea lead the groups out for the second time in 10 days, however this time we weren’t looking for Owens’ “Stingray beasts”, we were looking for their close cousins – Sharks. Estimating shark abundance can be challenging and one method of doing this is known as ‘longlining’. This method features a longline with baited hooks attached at regular intervals along the main line (called Ganjions). These Ganjions hang in the water column and are left to soak for at least an hour before being pulled back on board for inspection. The Bahamian government banned commercial longlining in 1993 to help protect shark species in the Bahamas, however it is still permitted for research purposes. Whilst the longlines were set to soak, we all got the chance to swim in an area where sharks are regularly seen. Sure enough, all groups were treated to fantastic sightings of Caribbean Reef Sharks (Carcharinus perezi) and Blacktip Sharks (Carcharinus limbatus). Two out of the three groups managed to catch sharks on the longlines. The sharks were brought alongside the boat and were consequently measured, tagged and released back into open water.
We were also lucky enough to get some amazing hands on experience with Green sea turtles with the help of Annabelle Brooks. Team Conch and Team Seagrass undertook the “Rodeo” technique of capturing the turtles, which involved jumping off the side of the boat and attempting to swim after the turtles to catch them. Team Starfish on the other hand, performed a different technique known as seine netting. We waded out into the water with the large (and heavy) seine net, forming a semi-circle between the beach and the bay. The net was then slowly pulled in and any turtles swimming within the semi-circle were caught and brought onto land. We all had the opportunity to help record measurements such as head size and carapace width, as well as tagging the turtles with flipper tags to help identify them in the future. After all the data was collected, the turtles were released back into the bay. At least 20 green turtles were captured across all 3 groups!
If you’d like to learn more about Brad, Owen and Annabelle’s research, check out the CEI website here: http://www.ceibahamas.org/research/
Or follow them on twitter:
@BradWeilerOn – Brad Weiler
@BarefootBrooks – Annabelle Brooks
@Shark_OOS – Owen O’Shea