River EstuaryTiger sharks have habitats that are usually very unpredictable (Fitzpatrick et al., 2012). They have been spotted as far north as Iceland as as far south as Uruguay (Marinebio, 2013). But, wherever they are in the world, they are mainly found in murky water or found in river estuaries, coral reefs, and lagoons, but can also be found at depths of 350 meters at times (Marinbio, 2013).

                                                    Courtesy of: Florida Museum of Natural History                                                             

Distribution MapWith such a large range of habitat, the migration pattern of tiger sharks is not fully understood, but the temperature of the water seems to have a large impact on the sharks as they are frequently found in warmer locations (Edmunds, 2008). Although it is still unknown whether they move strictly because of temperature, or because of the amount of food available (Edmunds, 2008). It is known that the tiger shark has adopted the same type of habitat as large sea turtles, which is one of the main food sources for the tiger shark (Witzell, 1987).  Whatever the reason is for these migrations, once one of these sharks leaves a particular site for another one, the time for return is very irregular, ranging from 2 weeks- 10 months (Edmunds, 2008).
    An experiment that further showed the unpredictability of tiger shark migration was conducted in 2012 on an island off the coast of Australia where a large population of sea turtles lay their eggs (Raine island). The researchers wanted to see if there would be an increase in tiger shark numbers while the turtles are laying there eggs (Fitzpatrick et al., 2012). While some sharks seemed to stay around the island for a longer period of time during this event, there wasn't enough evidence to say that the tiger sharks migration patterns were due to the sea turtle movement (Fitzpatrick et al., 2012).
    Another experiment suggested that tiger sharks use cognitive mapping when they move from site to site (Meyer et al., 2010). This could explain why the migration patterns of tiger sharks is so unpredictable. The cognitive mapping may arise from the exploration patterns of an indivual shark and can also possibly explain why Researcher found that some would stay at one site all year, while others would travel thousands of kilometers (Meyer et al., 2010).

Since the tiger shark is frequently found in shallow waters, human encounters happen frequently when compared to other sharks. Part of the reason for these attacks could be explained by man's expansion of civilization. This is very noticeable in Recife, Brazil, which has reported some of the highest rates of shark attacks in the world (Hazin et al., 2013). This happens for a couple of reasons, the first being from the destruction of the tiger shark's habitat (and many other organisms such as the Atlantic spotted dolphin and hammerhead sharks) from man made shipstructures such as ports, forcing the tiger shark to migrate to the beach areas (Hazin et al., 2013). Another reason is because of ship traffic in certain areas. Tiger sharks have been known to follow large vessels around and if these ships are going past beaches, there will be an increase of shark populations in those areas. There are a few hypotheses why sharks do this, one being that ships often times throw garbage overboard, giving the sharks an easy meal (Hazin et al., 2013).
    Even with the high attack rate in Brazil, the number of attacks worldwide are still relatively low. From 1580-2012, there have been 100 reported tiger shark attack, 71 of which were not fatal (Knickle, 2013). These attacks still unfortunately give sharks of all kinds a bad reputation. This bad reputation has consequently caused shark populations to drop from the over fishing of them (Marinebio, 2013).
    But we must change the publics opinion for the health of the ocean because sharks are responsible for keeping the ocean running properly. Being an apex predator, they remove the weak or sick fish, feed on dead carcasses, keep populations healthy by stopping the spread of disease, and ultimately keep the ocean populations in line (Sharksavers, 2013). Removing these creatures from the ocean would lead to devastating consequences on species as small as an ostracod to even animals that only spend part of their time in water such as a harbor seal (Sharksavers, 2013).

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December 2013