Sharks like to keep clean

Practical fish Keeping - 

Maintaining good hygiene is rendering sharks more vulnerable to humans, according a study published in a recent issue of the online journal PLoS ONE.

The study by Simon Oliver and coauthors investigated the interactions between the pelagic thresher sharks (Alopias pelagicus) and cleaner wrasses (the cleaner fish Labroides dimidiatus and the moon wrasse Thalassoma lunare) at a seamount (underwater mountain) in the Philippines.

Using remote underwater cameras at one of five cleaning stations in Monad Shoal in the Visayan Sea for 232 days over 16 months (between July 2005 and December 2009), the authors recorded more than 1200 hours of footage for analysis.

As the site is well known to tourists for observing thresher sharks, the authors also recorded the frequency and duration of recreational SCUBA divers visiting the cleaning station.

The authors recorded 97 instances of cleaning wrasses interacting with sharks during the period of their study. Nineteen of these interactions were interrupted, of which about one third were caused by the arrival of SCUBA divers (the other two-thirds were caused by the arrival of a second shark or ray).

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