The identification, behaviour and natural history of
SHARKS
of Florida, the Bahamas, the Caribbean and the Gulf of Mexico
EXTRACTS FROM THE BOOK


IDENTIFICATION
Its two dorsal fins and their placement make this species superficially similar to the lemon shark (page 80). Unlike the lemon shark, the sand tiger is more pointed than that of the lemon shark and the large teeth bristle noticeably from the mouth. The body can be marked with dull spots.

DISTRIBUTION
Irregularly distributed in temperate and tropical waters worldwide. In the northwestern Atlantic it occurs from the Gulf of Maine south to Florida and the northern Gulf of Mexico. It is also recorded from Bermuda and the Bahamas. In Australia it is called the grey nurse shark, in South Africa it is called the ragged-tooth shark.

SIZE
Probably reaches over 3 metres.

HABITAT
From shallow to fairly deep water. The sand tiger shark is occasionally seen by divers hovering in small groups in the immediate vacinity of wrecks.

DIET
This shark feeds, often in co-ordinated groups, on a wide variety of bony fishes. It also eats small sharks and rays, cephalopods and crustaceans.

COMMENTS
This is a relatively inoffensive shark whose ferocious appearance has led to its being blamed for attacks it has not committed. This species' tendency to form aggregations off deep-water wreaks has facilitated overfishing by sports fishermen

Doug Perrine
Shark Identification

This section describes basic identification features that should allow a diver with a good view of a shark to identify it. The sharks listed here are the species a diver is more likely to encounter in our region. They are grouped according to the following distinctive features for a preliminary assessment.



The diagrams give accurate taxonomic information about the various species. The small red sharks underneath a shark's name identify how dangerous this species is considered to ve a variety of contexts - to swimmers, surfers, spearfishermen and so on, rather than specifically to divers. The greater the number of small sharks, the higher the general threat - to a maximum of five.
 Warning signs

It has been known for some decades that certain species of shark will, under certain circumstances, alter their body posture as a warning sign that they might launch a pre-emptive attack against an animal that they perceive to be a threat or a compeditor. The Indo-Pacific grey reef shark was the first systematically investigated species. There are several features which combine to produce the classic so-called agonistic display:
the lowering of the pectoral fins
the raising of the snout
the stiffening or even cessation of the swimming motion
the contortion of the body into an unnatural curve.

As a shark will often lower it's pectoral fins to increase it's manouverablility, there is discussion as to whether this alone is sufficient signal of agonistic intent. Nevertheless, any shark that appears to be swimming erratically should be neither followed nor photographed (the firing of an underwater flash gun has been known to trigger an attack by the photographed shark). Agonistic warning signs by sharks appear to be considerably more widespread than was originally supposed.

I recently saw a remarkable piece of video footage, filmed by a diver in the Bahamas who got in the water with a large tiger shark that was attemting to feed on a leatherback turtle. As the diver swam towards the tiger shark, it lowered it's pectoral fins and began to swim in a slow, stiffened arc. When the woman ignored this, it turned, charged, and rammed her. It is not only of interest that shark displayed to her, but that it rammed, rather than bit her. This suggests that the tiger shark saw her as a competitor trying to help itself to the turtle the shark was assiduously hunting.....