Thresher Shark Encounter

[SharkDiverMag]

Did anyone take pics of any of these interactions?

Malpelo is the hot spot for threshers thats for sure. There are some cool stories on this thread. I've tried the bottle thing with white sharks...It didn't work very well. But I tried. I am going to try it on my next dive trip. It's pointless with sandtiger sharks though. They are around regardless. But I 've got a bull shark dive coming up, I'll try it then. I'll keep you posted!

cheers,

Eli

 

[murphdivers286]

Interesting technique. I wonder how many divers will be found dead with plastic bottles in their hands.....:lol:

 

[iainwilliams]

Hi:

Playing with bottles and white sharks is not exactly the most sensible thing to do. However, let me explain briefly why you did not get a reaction from the large predatory fish in comparison to a grey whaler - which at maturity is much smaller in size and statue.

But first, realise that biologists no little regarding white shark interactions, social behaviour, mating and other life processes.

It is highly probable that the white shark “heard” your bottle rubbing via the lateral line system, however, the shark choose to ignore the stimulus. Why? Because the white shark (WS) is probably the largest apex predator in the ocean. The WS is not exactly worried about anything other than a gang of killer whales, or a larger WS. Furthermore, WS are very cautious and usually approach slowly and methodically checking out there prey before they bite! In contrast to this, grey whalers are very flighty, territorial and exhibit a strong rivalry between themselves for prey. As a result, any stimuli in the water (from the bottle) will quickly attract them to the scene if they are unfamiliar with the stimuli.

Also note, that the bottle trick wears off quickly. After a few days rubbing bottles you will find the sharks grow tired of this routine.

To answer your question about photographs. Well, I have tried to unsuccessfully get good images. I have a poor resolution video I shot of a silvertip going through its paces, but as the resolution is quite low. The camera was a digital still camera that also has video.

Now onto something more serious and do not take this the wrong way. Sharks are dangerous marine animals that are unpredictable. Rubbing bottles with white sharks in the area is not a good idea……Iain

 

[Shiprekd]

Most "deep" water sharks are still unknown in terms of instinct signal reaction. A ton of theories abound but there is a definite difference between shallow water sharks and deep water sharks in terms of reaction to both lateral and electromagnetic receptor signals.

There is no "pissin' off" a shark. The animal is reacting to instinctive feeding signals and the amount thereof, that it's receiving. Rubbing a bottle is adding one more signal that triggers that feeding habit. You're puting off sounds and smells as it is. We think of ourselves as different and confusing to a shark. On the contrary, sharks don't have the capacity to think, only react. It's determined that new or unknown signals are deemed "food" and the shark will investigate further. Whether it's just a hit, or an all out assault.

Rub that bottle with an open cut somewhere and you're really askin to be given the ole bump test...

 

[archman]

Most "deep" water sharks are still unknown in terms of instinct signal reaction. A ton of theories abound but there is a definite difference between shallow water sharks and deep water sharks in terms of reaction to both lateral and electromagnetic receptor signals.

The benthic sharks tend to have better developed ampullae, to sniff out food in the muck. Dogfishes have superb senses of smell. Pelagics primarily cue in to auditory and olfactory cues to zero in on distant prey (the open ocean's a desert, remember). Vision's well developed in makos and their pals, which do high speed pursuits.

True "deep" sharks (living below 300m) have reduced nervous systems, as do most other deepwater critters. Nervous system's are energetically expensive to maintain, and the deep-sea is a VERY low energy environment. Vision is very poor, but likely cued to either red or blue wavelengths. Smell is outstanding. The acouticolateral line is usually highly reduced. I don't know about hearing or electroreception, sorry.

 

[Shiprekd]

LOL.. I knew someone would take a technical route over layman's terms. I just figured we would lose people if we got into it here, so I'll keep with the KISS method (Keep It Simple Stupid)

Electro-reception: A shark's electroreceptors (which are are multimodal, secondary sensory systems) can detect an electrical current and or change in their intensity as small as thirteen-billionths of a volt per inch. Deep water sharks rely heavily on their receptor, smell and vibration capabilitities due to the very point of poor sight/visibility as you pointed out. Which contradicts a "VERY low energy environment" statement or theory. Thirteen billionths of a volt is pretty low! if you look at it from the other side of the fence.

Hearing is a broad term. Most natural underwater sounds are produced in a very low 1,000 hz range. They definately don't have elmer fudd ears but through the use of their lateral system, they obvious can detect sounds and vibrations. Which are again, recognized as "cues" for instinctive feeding. This is just simple generalization.

Remember, I'm talkin about rubbing a bottle and a simplified reaction or chain of signals or "cues". If it took only one cue or signal to fire off a feeding instinct in a shark, I wouldn't be in the water with them every other day.

So, simply put, getting into the water alone is going to trigger a response in one form or another. How many in this class know the amount of electromagnetic current the human brain emits? heart? muscles? spinal system? - Now let's start factoring in vibrations from exhalation thru the regulator, an Octo or gauge console ticking against the BCD, How about that stubbed toe or oozing scrape on your foot, and now hey, let's just take a bottle and start rubbing it, causing low frequency sounds natural to underwater.

Sounds like all the ingredients for a bump or even a charge, no matter what type of shark.

I'll be more than happy to go into discussions about the temporal pattern of afferent impulse discharges of the Ampullae in dogfish with you, but this isn't the thread to do it in - I'm sure we would lose or bore quite a few people. No offense ladies and gents :O]

 

[isurus]

Eli
best I could do with the threshers in Malapascua, difficult conditions to take pics in. Not sure it would amke your magazine!

 

[iainwilliams]

Ah yes - all good information. I'm actually a rock doctor (geologist) - not a fish doctor (biologist), but I just love to be interdisiplinary and migrate between earth and life sciences - all good fun even if you do it as a job.............Iain

 

[SharkDiverMag]

I just want to see sharks. the bottle is one theory. And to answer Ian's question, I was not in open water with the whites when I tried it. I am not totally out of it. It was in a cage at Guadalupe Island. The sharks dissappeared for a couple of hours and I was trying to see if it would bring em back up. It didn't work. But hey I tried.

You all have some interesting perspectives. I'm stoked at the chat. The image is a bit rough, but hey you got to dive with a thresher! Not many people can say that. I can't. But we are trying our first attempt this year, we will see how it goes.

cheers,
Eli
www.sharkdivermag.com

 

[isurus]

You all have some interesting perspectives. I'm stoked at the chat. The image is a bit rough, but hey you got to dive with a thresher! Not many people can say that. I can't. But we are trying our first attempt this year, we will see how it goes.

cheers,
Eli
www.sharkdivermag.com

Actually I got to dive with (I think) 7 threshers on that dive. definitely 6 individuals. the macro on monad shoal is amazing too. I had 18 different sightings over the week of varying size/closeness inc. a huge gravid female. Also mantas!

heres a coupla' pics of other interesting species to demonstrate that I'm not completely useless with that camera and sharks (I like the weird little sedentary species)....

Heterdontus portjacksoni

Chiloscyllium griseum

Orectolobus maculatus