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wednesday night hammerhead


francomas777

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Terry H wrote:

Nice Scalloped Hammerhead.

They are ceratinly not deep sea sharks. The two most common hammerheads are Scalloped. We have caught them at Moreton Island (inside) and Inskip Point. You will find them in around river mouths, inlets, beaches, bays etc.

Yep, there spread right up the coast line,not a regular catch ,but not rare either.

In quieter, shallower areas they can sometimes be seen in groups of 5-6.

cheers Gad

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Fact Sheet: Scalloped Hammerhead Shark

The Scalloped Hammerhead Shark (Sphyrna lewini).

© K. Amsler

Biology of the Scalloped Hammerhead Shark (Sphyrna lewini)

Scalloped Hammerhead Sharks (Sphyrna lewini) are probably the most commonly found species of hammerheads located in coastal regions, appearing in very shallow waters such as estuaries and inlets. Their distribution in the water reaches from the surface down to a depth of approx. 275 m. The young, however, remain mostly in shallow waters along the shore to avoid the danger of falling into the mouths of predators. At certain times of the year and places, and during certain phases of their lives, scalloped hammerheads form very large schools, sometimes counting hundreds of individuals, but they also swim the oceans alone. Some populations remain stationary, others clearly wander, migrating in the direction of the poles in summer. Some sexually-related migrations have also been observed, e.g. females who undertake migrations during particular periods of their sexual development.

Appearance

The scalloped hammerhead shark belongs to the large hammerhead species, and like all representatives of this family, has the typically formed "hammer" consisting of a central dent and an arched front edge (hence the name). Another typical characteristic is the free end tip of the second dorsal fin which almost reaches the tail fin. Their coloring is mainly olive, bronze or light brown with a white belly. The edges of the fins are usually darker on young animals but becomes lighter as they grow older.

Size

Mature females can reach a length of more than 4 meters, the average length is, however, less. Males reach sexual maturity at a length of about 160 cm, females when they reach approx. 210 cm. The pups measure approx. 50 cm at birth.

Feeding

This hammerhead species feeds mostly on fish such as sardines, herring and mackerels, occasionally also on invertebrates such as octopuses. Large scalloped hammerhead sharks also eat small-sized shark species such as the Atlantic sharpnose shark (Rhizoprionodon terraenovae) or the blacktip reef shark (Carcharhinus melanopterus).

Reproduction

Scalloped hammerheads bear their young alive and have an egg yolk placenta. Pregnancy lasts between 9 and 10 months. Depending on their size, the females give birth to between 15 and 30 pups. The "hammer" is made of cartilage and is very soft when the young are born so as to easen the birth process. Young scalloped hammerheads grow relatively slowly when compared to other shark species.

Distribution

Scalloped hammerhead sharks are found practically around the world in the coastal regions of tropical, subtropical and moderate climate zones.

Behavior

As already mentioned, this shark species tends to form huge schools whose function is presumed to be manifold and may, among other things, concern feeding habits and reproduction. Although many studies also consider this behavior to be a group protective function, this is somewhat questionable since the animals have practically no natural enemies after reaching full maturity. Groups of scalloped hammerheads prefer staying in regions which have pinnacles or sea mounts which reach from great depths practically to the water's surface. Latest research also shows that these sharks can make use of the earth's magnetic field during their migrations.

Encounters with Humans

Although these sharks have definitely been involved in accidents, they are not really considered dangerous in the sense of being aggressive. Since they often appear in estuaries where visibility is very limited and where the influence of fresh water does not allow an optimal reaction of their electrical sensors (ampullae of Lorenzini), any accidents with humans are more likely a defensive reaction when surprised or frightened.

Similar Species

When it comes to size and appearance three additional species resemble the scalloped hammerhead and are commonly found in the latter's area of distribution. These include the great hammerhead (Sphyrna mokarran), the smooth hammerhead (Sphyrna zygaena) and the whitefin hammerhead (Sphyrna couardi). They can be differentiated by the form of their "hammers", the first dorsal fins and by color. Identification problems with the whitefin hammerhead are only possible in the latter's area of distribution which is limited to the Ivory Coast.

May be published only by indicating the source: Shark Info / Dr. Erich K. Ritter

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Rocket75 wrote:

making me think twice about taking the yak out now

rocket

hahaha,

in my younger,no responsibilities, have wheels will travel days,during parts of the 70`s early 80`s I did a bit of hand/gun spearfishing along the coast between Bundaberg and Townsville,the occasional, accidental encounters with noahs was ok,but when an encounter became,a skidmark leaving meeting, for me,probably just an over curious meeting for the noah,line fishing became my 1 and only fishing method.:lol:

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They are awesome critters although I think that about a lot of sharks :cheer:

Have caught them from Russell Island, waterloo bay, the eastern bay and outside. They are incredible to watch if you can see them free swimming during the day. Had a 5 to 6 footer chase a fish for ages and it was great watching him swivel his head trying to watch it as he got close then spin and do a 180 on the spot.

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that's cool...

last time i saw a hammerhead/s in the flesh i was down at around 50m and a school of about 20 of them was passing over me at about 20-25m. They were in the 6foot category mostly, a few smaller ones.

This was off Great Keppel island, there is a volcanic fault line out there, theory on hammers is that they tend to follow the fault lines alot, use them to navigate and stuff like that.... also the warmer water at breakthru points does cause an aggregation of marine life as well = dinner...

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Cool catch Franco. Would have been a nice surprise :woohoo:

Gad wrote:

Fact Sheet: Scalloped Hammerhead Shark

The Scalloped Hammerhead Shark (Sphyrna lewini).

© K. Amsler

Biology of the Scalloped Hammerhead Shark (Sphyrna lewini)

Scalloped Hammerhead Sharks (Sphyrna lewini) are probably the most commonly found species of hammerheads located in coastal regions, appearing in very shallow waters such as estuaries and inlets. ...

Encounters with Humans

Although these sharks have definitely been involved in accidents, they are not really considered dangerous in the sense of being aggressive. Since they often appear in estuaries where visibility is very limited and where the influence of fresh water does not allow an optimal reaction of their electrical sensors (ampullae of Lorenzini), any accidents with humans are more likely a defensive reaction when surprised or frightened.

....

May be published only by indicating the source: Shark Info / Dr. Erich K. Ritter

--------------------------------------------------------------------------------

Yeah right :whistle: 1018512.jpg

post-564-144598510716_thumb.jpg

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straddiebrad wrote:

WOW ellicat. I know the photos aren't yours but do you know the people in the yaks. Did they keep their cool or were they petrified. I know i'd be petrified, but I guess if you go out all the time in your yaks and encounter sharks often, maybe you get a little bit used to it, or know how to handle them a bit better.

Above quote was wriiten by myself (lel) not stradiebrad. sorry I posted this on my husbands log in accidently - he was logged in - I have just logged him off and logged myself on :blush:

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Angus wrote:

Nice one dude :)

There was actually a hammer head weighed in at one of the first BRC's caught from the new farm reach. However it was only about 70cm :P

Angus

Seen one getting caught at newstead park last week around 2 foot, the guy had no wire or anything and it was the middle of the day!

The river never ceases to amaze me!

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