Indian Ocean – 11 Day Cruise
Completed
A two week cruise was conducted in the Indian Ocean to study the behavior of sharks and other fish species swimming around fish aggregating devices despite piracy threats. The vessel visited eight different FADs in the Indian Ocean near the Seychelles islands and conducted several scientific experiments.
Scientists dived into the water to document the composition of different species around FADs and also observed the behavior of sharks around these floating objects. Some were captured and equipped with electronic tags, which allows the team to remotely observe the behavior of each tagged specimen for several weeks. The cruise addressed 4 of the 13 research activities identified in the project (labeled 2b, 2e, 3b and 4b), which are detailed below.
Research activities for the 2011 IO cruise (in no specific order)
Research activity 2b: Natural behavior of fish at FADs
Objective: To observe whether or not tunas and sharks regularly leave the immediate vicinity of the FAD during a 24-h cycle. This information could be used to target schools with less bycatch (see point 2c). Some of these FADs could be abandoned for long term observations of behavior (which will also allow the study of the ecological trap hypothesis), while others could be fished.
Research activity 2e: Attraction of sharks away from FADs
Objective: To test different stimuli (chum) to attract sharks away from the FAD shortly before the net is set.
Research activity 3b: Behavioral manipulations (e.g. attraction of sharks, small BET, other finfish)
Objective: To test different stimuli (chum) to attract sharks out of the net (when towing the FAD away), or others (e.g. light) to attract fish (e.g. small BET or other finsfish) towards an area in the net.
Research activity 4b: Survival of released sharks
Objective: To tag only the liveliest sharks (with pop-up archial tags – PATs) and release them as soon as possible to study their survival. The idea is to use MiniPATs from Wildlife Computers (WC) as most of sharks will be small.
Blood samples will be taken to establish baseline data on stress levels at the time of release.
