Snorkeler Killed by Sharks in the Bahamas

[HalcyonDaze]

If individual sharks are moving randomly and without any pattern over a range that constitutes approximately 1/4 of the Atlantic Ocean (as was described above by Halcyon), then the probability that the same shark would make an appearance at the same wreck for multiple days over multiple years is NOT indicative of random motion. The wreck is too little and the described "random wandering range" is too large for me to accept the explanation of "random wanderings over 1/4 of the Atlantic".

It's sorta like the same (winning) lottery number being selected by one person for 3 years in a row on the same month of the year. Just seems that the assumption of "random wanderings" is contradicted by the frequency of repeated observation of the same shark at a unique location.

Unless of course, you might guess that these sharks DO move randomly, except when they are presented with unique and important feeding opportunities? Would that explanation fit the observations?

Read my clarification in Post 179, as well as the following from the Guy Harvey Research Institute:

The handful of studies that have examined tiger shark movements have revealed what appears to be inconsistent migratory behavior among individuals - with some sharks staying relatively local, others migrating long distances mostly along coastlines, and a few moving huge distances across ocean basins.

In other words, no obvious behavioral patterns have emerged and the picture of tiger shark horizontal and vertical movements remains unclear.

Granted, I sat in on that lecture about two years ago. They may have been able to tease an overall pattern out since then, although the wording of this statement makes me think we're still looking at a lot of individual variation; I bolded and underlined one line to highlight it:

The results from long-term tracking of sharks tagged in Bermuda are showing that in the western North Atlantic, adult tiger sharks display detectable patterns of movements and clear evidence of residency "hot-spots" that appear to be seasonal. The overall patterns detected for adult sharks are that they migrate south along a broad corridor from Bermuda to the Bahamas (mainly) and some sections of the Antilles, where they overwinter. The sharks then embark on northern migrations during spring and summer months, spending 5-6 months in the open ocean, north of Bermuda and in many cases almost in the middle of the Atlantic Ocean!

This makes one wonder what they are doing so far out in the Atlantic Ocean after spending 6-8 months so tightly associated with island habitats in the Bahamas and Caribbean.

Something must be attracting these sharks into the deep open-ocean far offshore. Are they out in nearly the middle of the north Atlantic for mating? For feeding? The causative factors driving this behavior remain unknown. Notably, these tiger sharks are displaying a remarkable ability to drastically switch their habitats comfortably, using shallow, island environments (presumably coral reefs and seagrass habitats) for part of the year and completely open-ocean, deep environments for the other part. Few other shark species show this flexibility.

The study is continuing with tracking more tiger sharks in the western Atlantic. We have also expanded this study into the Indian Ocean.

Source (sadly, the links to the tracking pages appear to be broken): Track Your Tiger Shark Migration! | Guy Harvey Research Institute

 

[johndiver999]

Thanks for the information and detailed explanation. It seems like I took a few of your somewhat causal comments and read more into them than was intended.

So they utilize an incredible diversity of habitats over the course of a year. It is fascinating to try to think of what energetic benefit is derived from these types of long range migrations through so many different habitats.

 

[HalcyonDaze]

White sharks seem to do the same thing; for a long time they were thought to be coastal species tied to seal colonies. Now we know they also range over long distances and at least some spend large chunks of time out in the open ocean. That hasn't been figured out either. It could be for mating, thermal regulation, or it could be for following certain types of prey. During one of my graduate seminars the lecturer was of the opinion that white sharks traveling from California to Hawaii were probably correlated with humpback whale movements; an injured or dead whale will certainly attract a lot of sharks and that kind of meal will last a long time. There's also some indication big sharks like whites and tigers will hunt ahead of a front (the boundary between water masses of different temperatures) as the food chain tends to congregate there. What I was really interested in before going into graduate school was the idea of how they can not only navigate over long distances but find things like eddies and upwellings; are they just winging it, or do they have the sensory and mental capabilities to know where to look?

The takeaway I get from that is that these are animals that don't get stuck in a rut; they can find food in a lot of different environments and generally take their pick of options. As stated previously I think the reason we're seeing fewer tigers in Jupiter is because they've gotten to a size where a few chunks of bonita aren't really that interesting; what we think they're in the area for at that time of year is all the sea turtles that are mating and nesting.

One of the reasons I enjoy shark diving is that it does give you a better understanding of the animal; anyone who thinks they are "sea puppies" is definitely asking for a rude awakening but your threat assessment gets a lot more nuanced than "it'll kill me if I'm in the water with it." Back when I did my first few shark dives in Florida I would get freaked out by a veritable sharknado of lemons; a year later I was popping lionfish in the middle of the pack and getting them up to the surface without too much concern. It does help dispel the gut fear a few people in this thread have expressed; one of my concerns is that following the fatal attack at Rose Island every normal nip and bump is going to get splashed over the headlines as evidence of an outbreak of shark bites. And that can lead to consequences; last year there were reports that a dozen or more big tigers were killed by fishermen out near Abaco while feeding off a whale carcass. I would rather people understand that the ocean is not a sanitized swimming pool; it is every bit the wilderness the Serengeti, Amazon, or Everglades is and that includes being on watch for large predators.

 

[chillyinCanada]

I wonder if the victim was wearing any jewelry? The only reason I brbri this into it is because it was suggested by another poster at the time we discussed this event:

Bahamas shark bites off North Carolina woman's arm

 

[HalcyonDaze]

The family has spoken to the press in California: Family says no one jumped in to help woman killed in Bahamas shark attack

Dr. Chris Lowe having been one of my thesis advisors, I offered my condolences on being quoted along with Erich "If You Keep Your Heart Rate Low (Or if There Isn't a Cameraman Around To Blame), You Won't Be Attacked" Ritter.

 

[Dan]

The family has spoken to the press in California: Family says no one jumped in to help woman killed in Bahamas shark attack

Dr. Chris Lowe having been one of my thesis advisors, I offered my condolences on being quoted along with Erich "If You Keep Your Heart Rate Low (Or if There Isn't a Cameraman Around To Blame), You Won't Be Attacked" Ritter.

“Once both women were out of the water, the family said the staff had no first aid kit or basic supplies for any type of injury — and provided no first aid “whatsoever.”

“It felt like a lifetime as they waited for a boat to arrive. When the small boat arrived, it contained only a bench and a staff member driving. A staff member waiting with Jordan and Kami, helped Kami get Jordan into the boat and the 4 of them drove off to Nassau,” the statement added. “There were no medical or emergency supplies in the boat. The only thing provided were towels which were used to cover Jordan’s legs.”

The family said a waiting ambulance at the dock transported Jordan and her mother to a hospital, where she died.”

 

[AfterDark]

No heroes on the beach that day, evidently.

 

[The Chairman]

Once both women were out of the water, the family said the staff had no first aid kit or basic supplies for any type of injury — and provided no first aid "whatsoever."

I'm finding this to be quite common outside of the USA. The resort where I broke my leg had absolutely no medical supplies, or didn't know where they were. It's going to be a question I start asking from here on out.

 

[AfterDark]

I'm finding this to be quite common outside of the USA. The resort where I broke my leg had absolutely no medical supplies, or didn't know where they were. It's going to be a question I start asking from here on out.

I have a trauma/first aid case I've taken to both the gun range and diving for years. Don't think however it would have done much good that day. The poor girl's injuries were many and massive.

 

[The Chairman]

The poor girl's injuries were many and massive.

A tourniquet might have helped. Problem is, people get trapped in their own little boxes. Adapt, improvise and overcome should always be your mantra in a time like that. The resort didn't have any splints, so they made some. They didn't even have any bandages, but someone in the crew had some ace bandages. Don't let fear or pain paralyze you. They could have made a tourniquet out of many things, and who knows? They might have.