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Shark bites Kanaha Kiter
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U2U2U2



Joined: 06 Jul 2001
Posts: 3077
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Mon Nov 18, 2013 10:53 am    Post subject: Reply with quote

The tiger shark is considered a near threatened species due to finning and fishing by humans. since we are , as humans, intentional or not, trying to make the Tiger shark extinct, they are pissed.

have a keen interest in sharks, and read quite a lot. The really dangerous ones are Great White and Bull, but apparently the others don't read the same books.

the below link is worth a look, as it shows what sharks are there and where they should normally swim



http://www.hawaiisharks.com/incidents.html

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shreddbob



Joined: 31 Mar 1987
Posts: 279
Location: Massachusetts

PostPosted: Mon Nov 18, 2013 10:41 pm    Post subject: Reply with quote

U2^3, I was looking at that site too. Lots of info.

Below are the Maui shark incidents since 2001, plotted on a study map that shows man caused nitrogen levels around Maui.

[The map I borrowed is taken from :Article in Press: Dailer, M.L., et al. Using d15N values in algal tissue to map locations and potential sources of anthropogenic nutrient inputs on the island of Maui, Hawai‘i, USA. Mar. Pollut. Bull. (2010), doi:10.1016/j.marpolbul.2009.12.021]
http://coralreefecology.ucsd.edu/files/2010/09/Dailer_et-al_2010_MPB.pdf

I was curious if the water treatment facility in Kahului, or at other locations, was somehow attracting sharks/attacks. I have manually over-layed the attack locations onto this (below shown) map, I was trying to see if water treatment plant pollution has any correlation. The numbers on the map are related to human caused nitrogen run-off. The higher the nitrogen number the more human related pollution in the water.

Purple arrows are Tigers. Yellow arrows are either reef shark, or "undetermined. Not included are "provoked" attacks where spear fishermen have catch strung up. Recent Tiger attacks DO seem to have been concentrated around higher nitrogen numbers of >5 (going back to 2009). But when I took the attacks back to 2001 the Tiger attacks don't fit this pattern so well. Anyway, I thought it's interesting to see where all the incidents have happened around the island in the past 14 years. It's also illuminating to see the water quality...

To see map larger, right click to open in new window.



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Last edited by shreddbob on Mon Nov 18, 2013 11:49 pm; edited 5 times in total
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shreddbob



Joined: 31 Mar 1987
Posts: 279
Location: Massachusetts

PostPosted: Mon Nov 18, 2013 10:45 pm    Post subject: Reply with quote

Also, I'm surprised to learn that October (Fall wave season!) is prime month for Tiger attacks.

http://hawaiisharks.com/sharkspeople.html

And also:

http://mauinow.com/2012/12/06/analysis-whats-with-all-the-shark-attacks/

In the above link, Marine biologist Carl Meyer is interviewed--the Maui Now article states the following:

The prevailing theory at the moment is that female tiger sharks migrate from the Northwestern Hawaiian Islands region to the main islands at this time of year presumably to pup (give birth), including in shallow waters where people swim. Whether it’s the pupping that leads to more aggressive behavior, or just that an increased presence of sharks lead to a higher likelihood of attacks, is unclear.

That theory’s origins come from a recent study by Carl Meyer, assistant researcher with the Hawaii Institute of Marine Biology. Over 100 tiger sharks have been tagged and tracked over two decades, leading to the findings.

Meyer’s theory seems to coincide with data recorded by the state Division of Aquatic Resources. Historically, there is a clear increase in attacks September through November, while the least amount of attacks occur in the summer (despite more people being in the ocean), according to the DAR’s Maui-based Education Specialist Russell Sparks.
It doesn’t explain the higher number of attacks this year compared to other years though, despite what is being widely reported in other media. Meyer says the statistical link between the migration period and the attacks is hard to determine, due to factors such as the low number of attacks comparatively (e.g. three last year versus nine this year) and that tiger sharks were not positively identified as the attackers in every case.
But the state’s data does beg the question of exactly how much more dangerous it is being in the water now (fall to winter) rather than other times. Of Hawaii’s nine attacks, five of them happened in Maui waters this fall [fall 2012, when this article was written] in a 90-day window.



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beaglebuddy



Joined: 10 Feb 2012
Posts: 710

PostPosted: Tue Nov 19, 2013 1:26 am    Post subject: Reply with quote

Several points, In the summer there are more people in the water but they are mostly very near shore just swimming around in the shallows, there aren't really many people surfing because there are no waves in the summer but come Sept thru Nov that is when the first winter swells roll thru and the surfers flock to the water in great numbers and they aren't just near shore.
Also the sewage treatment plants are in the more populated areas and that is of course also where more people are in the water.
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stevenbard



Joined: 11 Nov 1993
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PostPosted: Tue Nov 19, 2013 2:03 am    Post subject: Reply with quote

There are a lot of very bright guys on this forum! Very interesting data. I can't tell you how many times I've just dropped my sail outside the reef and hung out waiting for a set, or just rested in light winds.

Now I'm getting that "Jaws" feeling I never had.... Embarassed Lowers will never be the same to me...at least in October and November. Confused
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shreddbob



Joined: 31 Mar 1987
Posts: 279
Location: Massachusetts

PostPosted: Tue Nov 19, 2013 8:41 am    Post subject: Reply with quote

Beaglebuddy, good points.


stevenbard wrote:


Now I'm getting that "Jaws" feeling I never had.... Embarassed Lowers will never be the same to me...at least in October and November. Confused


I try not to think about it too much when I'm sailing there, though I try not to blow jibes on the outside. Perspective: Way more likely statistically to get injured in the car on the way to the beach.
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U2U2U2



Joined: 06 Jul 2001
Posts: 3077
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Tue Nov 19, 2013 9:42 am    Post subject: Reply with quote

shredbob

what I find most interesting in your chart shows no reports in the NE sector, and SW I think one. Obvious the area that have lots of activity have the most attacks, do those areas get little activity ?

the water/chemicals being released, or runoff is curious , have the sharks become accustomed to it, and hang around ? Iam thinking your thoughts are that something is an attractant to one the tigers senses.

The Tigers are quite a bit larger than the others there, so easier to ID with the stripes as well, the others would be hard to ID, cept the hammerhead.

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stevenbard



Joined: 11 Nov 1993
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PostPosted: Tue Nov 19, 2013 12:01 pm    Post subject: Reply with quote

Two thoughts:

1: Why are there chemicals (nitrogen) being dispersed? I thought they were discharging clean water. Even though not scientific, it seems you are correct that something is attracting the sharks to the area around the facility. I suppose it just could be that it's a large natural harbor.

2. The fall stats are significant enough to warrant caution when dragging around and swimming while under powered. IOW, I'm not going to jump in and swim outside the reef any more!
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scottwerden



Joined: 11 Jul 1999
Posts: 216

PostPosted: Tue Nov 19, 2013 12:37 pm    Post subject: Reply with quote

U2U2U2 wrote:
shredbob

what I find most interesting in your chart shows no reports in the NE sector, and SW I think one. Obvious the area that have lots of activity have the most attacks, do those areas get little activity ?



The NE part of Maui is very rugged. No beaches, little access to the shore. SW is similar up to the Ahihi-Kinau Reserve where there are tons of snorkelers. In fact it was at Ahihi where the woman died last summer from a shark bite.
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shreddbob



Joined: 31 Mar 1987
Posts: 279
Location: Massachusetts

PostPosted: Tue Nov 19, 2013 10:21 pm    Post subject: Reply with quote

I think the other thing that stands out is the single attack only at Olowalu. That whole area of West Maui, north to Lahaina and south to where the coast takes a bend near "Grandma's" is loaded with sufers. People say Olowalu is overdue. I do see relatively low nitrogen run-off numbers along that coast, certainly no big numbers like around the 3 water treatment facilities elsewhere.
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