Skip to content

SANParks.org Forums

View unanswered posts | View active topics






Post new topic Reply to topic  Page 1 of 1
 [ 4 posts ] 
Author Message
 Post subject: Shark: Ragged Tooth Shark
Unread postPosted: Wed Dec 14, 2005 2:21 pm 
Offline
Distinguished Virtual Ranger
Distinguished Virtual Ranger
User avatar

Joined: Thu May 26, 2005 12:00 pm
Posts: 530
Location: At work longing for the outdoors!
Since i was once 1m away from a big raggie during a dive, something i will never ever forget, i think it is appropriate to give some info on them :lol:

This large coastal species of shark occur in most subtropical and temperate oceans.
They are also known as the Sandtiger shark and the Grey Nurse although the different populations never meet up due to geographical distribution.
They are generally coastal, usually found from the surf zone down to depths of around 25m.
However, they may also occasionally be found in shallow bays, around coral reefs and, very rarely, to depths of around 200m on the continental shelf.
They usually live near the bottom, but may also be found throughout the water column.

They swim slowly with their mouths open, exposing a permanent toothy grin that reveals dagger-like, narrow double-edged teeth making it appear ferocious ( :shock: trust me it does!!!)
In most sharks the teeth are only exposed when the shark opens its mouth.
Despite their menacing looks raggies, as they are affectionately known in South Africa, are considered docile.
8) No human remains have ever been found in a ragged tooth shark and there is also no scientific evidence that they will attack humans unless provoked.
Instead they feed on a wide range of fish, smaller sharks, squids, rays and lobster.

They have a number of characteristics and behavioural patterns which make them markedly different to other sharks.
In particular, schools of ragged tooth sharks (which can number up to 80 off the South African coast) have been observed to feed cooperatively, marine scientists report rare sightings of watching raggies work together to bunch up food and then eat it collectively.
The teeth of the ragged tooth shark are very different to those of the white shark.
Raggies' teeth are sharp, round and curved and are designed to hold their prey while they swallow it whole. The white shark, on the other hand, has sharp, heavy, triangular teeth for cutting their prey, such as seals, firstly to kill them and then to reduce the carcass to manageable pieces.

Raggies cannot swallow whole fish tail first as the fish's dorsal fins catch in the shark's throat.
Therefore, when a raggie catches a fish from the tail end it must work it around in its mouth until it can safely be swallowed head first.
This is done using a series of quick snapping movements as the raggie dare not drop its prize for fear of it being grabbed by another prowling raggie.
While doing this, the raggie's jaws are extended forward with their teeth protruding, a very scary sight when you are only centimetres from the action.

Most large sharks are committed to a life of perpetual motion so that oxygenated water passes over the gills.
The raggie is one of the few large sharks capable of remaining stationary and actively pumping water over the gills.
This is how come 40% survive the shark nets.
If left too long however they too drown.
The ability they have to pump water over their gills reduces the energy spent in swimming and enables the shark to remain motionless in the water column.
This in itself gives rise to another problem: sharks are negatively buoyant and lack the swim bladder found in bony fish that helps to maintain position.
The raggie has a neat answer to the problem; it ventures to the surface to swallow air that is then retained in the stomach thereby simulating a swim bladder.

_________________
Be more concerned with your character than your reputation. Your character is what you really are while your reputation is merely what others think you are.
Please help save Mapungubwe NP - Facebook page


Top
 Profile  
 
 Post subject:
Unread postPosted: Wed Dec 14, 2005 2:25 pm 
Offline
Distinguished Virtual Ranger
Distinguished Virtual Ranger
User avatar

Joined: Thu May 26, 2005 12:00 pm
Posts: 530
Location: At work longing for the outdoors!
One of the most fascinating aspects of the life history of the ragged tooth shark is its mode of reproduction.
Unlike many other solitary sharks, raggies swim in packs and each receptive female will be exposed to several males.
The scarring, which inflicts little damage to their thick skins, is often extensive, suggesting that several males may have attempted to mate. After mating in the colder waters of the KwaZulu Natal in South Africa the females journey north into the warm, azure blue waters of Maputaland. Packs of pregnant females may be found on the shallow reefs off Sodwana and as far as Mozambique. The warmth of the water accelerates embryonic development.
They then begin the return journey to the Eastern Cape of South Africa where they give birth to two pups measuring approximately one metre.
The most unusual part of this process is the fact that as many as 10 embryos may be present in each of the two uteri, but few of them survive for more than a few days.
Thousands of pea-sized eggs are produced in a single functional ovary that enters the uterus. The first one in each uterus to reach a suitable size begins to feed on its siblings over a gestation period of nine to twelve months. This intra-uterine cannibalism is unique to the ragged tooth shark and is a rather bizarre example of the survival of the fittest – a phenomenon found throughout the animal kingdom.

_________________
Be more concerned with your character than your reputation. Your character is what you really are while your reputation is merely what others think you are.
Please help save Mapungubwe NP - Facebook page


Top
 Profile  
 
 Post subject:
Unread postPosted: Wed Dec 14, 2005 2:37 pm 
Offline
Distinguished Virtual Ranger
Distinguished Virtual Ranger
User avatar

Joined: Thu May 26, 2005 12:00 pm
Posts: 530
Location: At work longing for the outdoors!
The Status of Ragged Tooth Sharks

Ragged tooth sharks are under threat in many parts of the world and the species is listed as Vulnerable by the World Conservation Union (IUCN 2000) Red List of Threatened Animals.
The Red List rationale is based on the fact that ragged tooth sharks have one of the lowest reproductive rates known among sharks (one to two pups every other year), and that it is late in maturing (6-12 years) resulting in it’s inability to sustain heavy fishing pressures.
In 1984 ragged tooth sharks became the world’s first protected shark species, following their targeted hunting by fishers and spearfishers in Australia and their subsequent decimation in the 1960’s.
Despite the implementation of a comprehensive recovery plan in Australian waters, they are showing no signs of recovery and are listed as Critically Endangered.
:shock: A recent report has found that they could be extinct within six years unless drastic measures are implemented to protect them in this area.

Internationally they have come under mounting pressure; off the coast of the United States ragged tooth sharks are rare (80-90% decline) and are presently protected.
The decline has stopped but recovery is not apparent. They are now absent from the Eastern Pacific, and in the Mediterranean and East Asia they are rare.
Although ragged tooth sharks are commercially protected in South Africa, there has been little research into the biology of these animals and their population status is largely unknown.

_________________
Be more concerned with your character than your reputation. Your character is what you really are while your reputation is merely what others think you are.
Please help save Mapungubwe NP - Facebook page


Top
 Profile  
 
 Post subject: Re: Shark: Ragged Tooth Shark
Unread postPosted: Wed Jun 27, 2012 1:57 pm 
Offline
User avatar

Joined: Sun Mar 04, 2007 7:06 pm
Posts: 46
Location: Australia
Hi,

During a Sharks of Southern Africa expedition during March 2011, we were lucky enough to see a Raggie (Grey Nurse over here in Oz - by the way I prefer Raggie) air gulping. We were off the De Hoop reserve, and at first we thought it was a small Great White breaching! But it was a Raggie, and I think we were very lucky to see it do that.

I read the other day that their not protected in South African waters, does anyone know why that is? It's such a critically endangered shark everywhere it's found, and needs all the help it can get. Despite their aggressive appearance they really are a calm shark to dive with, and very unique.

I'm a big shark lover, and it's so sad to see whats happening to the worlds shark populations. Asian demand for shark fin just keeps increasing, thank god for Sea Shepherd and their like out there fighting for what the governments of the world see simply as dollar signs.

To finish on a positive, I'm heading to South Africa next month to help study Great Whites in Gansbaai and can't wait to those incredible animals again. If anyone over there hasn't done it yet, I highly recommend it as seeing such a majestic predator in the ocean will be guaranteed a highlight of your life!

_________________
Take nothing but pictures, leave nothing but footprints

19/11 Skukuza
20/11 Berg en Dal
21-22/11 Satara
23-26/11 Olifants wilderness trail
26/11 Letaba
27/11 Olifants
28/11 Skukuza


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 



Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group

Webcams Highlights

Addo Nossob Orpen Satara
Addo Nossob Orpen Satara
Submitted by kyknetta at 19:07:34 Submitted by kyknetta at 08:52:58 Submitted by stu at 12:27:23 Submitted by ritad at 10:34:02