Abstract
An abnormally high shark attack rate verified off Recife could be related to migratory behavior of tiger sharks. This situation started after the construction of the Suape port to the south of Recife. A previous study suggested that attacking sharks could be following northward currents and that they were being attracted shoreward by approaching vessels. In this scenario, such northward movement pattern could imply a higher probability of sharks accessing the littoral area of Recife after leaving Suape. Pop-up satellite archival tags were deployed on five tiger sharks caught off Recife to assess their movement patterns off northeastern Brazil. All tags transmitted from northward latitudes after 7-74 days of freedom. The shorter, soak distance between deployment and pop-up locations ranged between 33-209 km and implied minimum average speeds of 0.02-0.98 km.h-1. Both pop-up locations and depth data suggest that tiger shark movements were conducted mostly over the continental shelf. The smaller sharks moved to deeper waters within 24 hours after releasing, but they assumed a shallower (< 50 m) vertical distribution for most of the monitoring period. While presenting the first data on tiger shark movements in the South Atlantic, this study also adds new information for the reasoning of the high shark attack rate verified in this region.
Highlights
Understanding the factors that elicit repeated shark attack events on humans in a local scale is essential in every sort of aspects
If tiger sharks off northeastern Brazil are moving northward under the assumption that sharks are being attracted shoreward towards Suape by incoming vessels, one might predict that they would subsequently visit the littoral area of Recife
The Suape port was built in a large, mangrove-bordered estuarine system which used to be relatively pristine until construction activities inflicted intense habitat degradation, including the partial barring of two of the four rivers previously discharging in this system
Summary
Understanding the factors that elicit repeated shark attack events on humans in a local scale is essential in every sort of aspects. Hazin et al (2008) suggested that potentially aggressive sharks occurring off Recife could be moving downstream following northward coastal currents, which would lead them from the coast of Suape directly to the beaches of Recife where most attacks occurred. This would be most applicable in relation to tiger sharks, which have wide home ranges (Meyer et al 2009) and have been reported to perform long-distance movements in a short amount of time (Heithaus et al 2007, Kohler et al 1998). This note investigates the regional movements of tiger sharks caught off Recife and addresses the implications of such movements regarding local attack hazard
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