The Historic Project shark team has begun to examine and compare the preliminary results from the November 2012 expedition with the previous two expeditions. The data from both November expeditions seems to show similar patterns of a higher Caribbean reef shark species abundance compared to tiger sharks; the two dominate total species captured for this project. This is the opposite of the historic data, as tiger sharks historically had a higher abundance.
The total catch for November 2011 was 52 sharks over 5 scientific longline sets. The catch per unit effort (CPUE; number of sharks caught per unit of time) from November 2011 was 0.12 Caribbean reef sharks per hour, dominating catch rates at 79% of the total catch. The CPUE for tiger sharks was 0.02 sharks per hour and 17% of the total catch, with the rest of the catch consisting of silky sharks. November 2012 total catch was 36 sharks over 4 research sets. CPUE for Caribbean reef sharks was 0.07 sharks per hour, comprising of 86% of the total catch. The remainder of the catch consisted of tiger sharks, with a CPUE of 0.01 sharks per hour. Due to rough weather the crew was only able to set 4 research lines, resulting in a fewer number of sharks in November 2012 than 2011, although the numbers are still comparable. Interestingly, the March 2012 expedition showed a more equivalent species catch rate. Thirty-two sharks were caught over 6 sets, with Caribbean reef sharks’ CPUE at 0.039 sharks per hour and 47% of the total catch, and tiger sharks’ CPUE at 0.044 sharks per hour and the rest of the total catch. Continue reading
After visiting the Blue Ocean Film Festival as finalists in September, Ian Rossiter (Flats Team intern) and Brendan Talwar (Shark Team intern) submitted their film to the Festival Mondial de l’Image Sous Marine (World Festival of Underwater Images) in Marseilles, France. After a few weeks, they received an email announcing their first award, granted by the French Federation of Film and Video. With this exciting announcement came the news that winning films would be shown across the world at small film festivals everywhere.The first venue to showcase the winning films was the Miami Underwater Festival from November 30 to December 2, 2012, where the Story of Sharks was shown to young audiences at the Miami Science Museum. On the same weekend, the video was shown to the Bahamian Minister of the Environment at the Cape Eleuthera Institute/Island School Research Symposium. The next step is submission to a few more festivals around the Bahamas and United States before distribution online. (Photo of Brendan (L), Ian (R), and their mentor, Didier Noirot).
Brendan Talwar, research assistant for the Shark Conservation and Education Program, has been working on a research project during his time at CEI. Here he describes his research:
My research focuses on the use of unbaited video cameras placed in the mouth of tidal creek
systems. I’m using this method to investigate the behavioral ecology of elasmobranchs, focusing on the lemon shark (Negaprion brevirostris). These sharks enter mangrove creek systems during incoming tide to seek refuge from predators, as well as to forage among the mangrove prop roots.Given the plight of shark populations worldwide, and the lack of non-invasive methods of population assessment, the use of unbaited video in coastal ecosystems will lay the groundwork for completely hands off research techniques in the future.
The Historic Project shark team went out to “the bridge” November 21st and 25-28th and camped out at Half Moon Cay for their third exciting expedition. The data analysis is currently ongoing, but there were several highlights from the trip. While hauling the gear after a scientific longline set, the shark team witnessed an estimated 2.5 m (8 ft) blue shark free swimming alongside the boat! It was a first for everyone on board to see a blue shark, and came as quite a surprise as blue sharks typically prefer deeper, cooler waters. On a different set the team witnessed another new species – this time up close and personal as a 1.8 m (6 ft) shortfin mako shark was hooked on the line! And as if those species weren’t enough, the shark team caught their biggest shark of the three expeditions, a 4.1 m (13.5 ft) long tiger shark! It was a successful final November expedition, with the data starting to show some interesting trends. A big thank you goes out to everyone at Half Moon Cay for providing food and a warm shower at the end of the day.
November marks the beginning of CEI’s Shark Research and Conservation Program’s third field expedition for the Historic Bahamian Shark Abundance Project. Led by Shark Research and Conservation Program Director, Edd Brooks, and Jeff Stein, Senior Research Scientist from the University of Illinois, the project is replicating a series of fisheries-independent longline surveys, which took place over 30 years ago, from 1975-1982.The original dataset was collected by Captain Stephen Connett of the vessel R/V Geronimo, which conducted the initial surveys on the shallow bank known as “the bridge,” that connects the southern tip of Eleuthera to the northern tip of Cat Island. The initial surveys documented a total of six species, however the majority of the catch was dominated by tiger sharks (Galeocerdo cuvier) at 54% of the catch, and Caribbean reef sharks (Carcharhinus perezi) at 33%.
Funding for four expeditions to the bridge was obtained in 2011 and to date two have been completed. Preliminary analysis of data from the previous expeditions (November 2011, March 2012) is already providing us with some valuable results. After 12 scientific longline sets the crew has caught 84 sharks from three species and has documented a shift in the assemblage compared to the historical dataset. Now, Caribbean reef sharks represent 67% of the catch and tiger sharks only 31%. Continue reading