Dr. Lawrence Cahoon on 3 Shark Attacks on NC Coast from June 11 to June 14, 2015

We asked Dr. Lawrence Cahoon, Professor of Biology and Marine Biology at the University of NC Wilmington the below question in regards to the three shark attacks occurring between June 11 and June 14, 2015 at two beaches located in Brunswick County NC.

Based on the recent events outlined below, what is your scientific analysis per the questions presented?

On June 11, 2015: A 13-year-old girl was injured after a shark attacked her and bit her boogie board in Ocean Isle Beach in North Carolina. (IBM Times)
On June 14, 2015: A 13-year-old girl and 16-year-old boy each lost an arm Sunday in separate shark attacks at the same North Carolina beach. Oak Island Mayor Betty Wallace told CNN tat the female swimmer was attacked first, around 4:15 p.m. Less than 90 minutes later, as responders were still tending to her, the boy was attacked. (CNN)

june-2015-nc-shark-attack-map

Question #1:

Do you think this is indeed a shark attack, or do other species come into play such as the Barracuda species (mainly the Great Barracuda) and/or schooling Bluefish?

Dr. Cahoon:

These were definitely shark attacks. The bite marks on the boogie board were clearly shark bites. The more serious attacks at Oak Island, in which limbs were bitten off, had to be sharks. Barracudas are rare in NC inshore waters, although I have seen them offshore. Schooling blues would create laceration injuries at best, not whole limb amputations.

Question #2:

Do you think these three assumed shark attacks are from the SAME SHARK?

Dr. Cahoon:

I think the first incident was a smaller shark mistaking the boogie board for more typical prey, like a skate or ray. Note that it bit the girl once and the boogie board twice. The other attacks were more likely a larger shark, probably a bull shark. It’s possible that the same shark might have been responsible for the two Oak Island attacks, but we will never know.

Question #3:

Given the fact these three incidents occurred along the beaches of Oak Island and Ocean Isle Beach, do you believe outflows of outlet/inlet river systems presented a problematic situation for low visibility conditions, thus providing the possibility of “mistaken identities” per the attacking species natural prey?

Dr. Cahoon:

I think the first attack was mistaken identity. The latter two may have been more deliberate. Bull sharks are considered more dangerous to humans than other surf zone sharks – more aggressive and often large enough to do real damage. Visibility is much less significant than people think. Visibility in ocean water is typically very limited. I used to SCUBA dive offshore, and visibility as high as 50 feet was considered excellent. Nearshore visibility is always poor. Sharks do not use vision as their primary sensory mode, although humans do (and that difference confuses us). Sharks rely primarily on auditory sensing (hearing) to detect prey. Sound travels very well in water. Sharks, like other fishes, hear with a lateral line system of pressure wave sensors running along each side of their bodies. They can hear sounds of very low frequency as a result – much lower frequencies than we can handle – and low frequency sound travels far in water. Sharks can hear swimming noises, consequently they know of our presence at substantial distances. The fact that they are there, we are there, and they know we are there, but attacks are so very rare is strong evidence that they almost always ignore or avoid us.

So, the first attack was a smaller shark likely confused by splashing and the sounds/appearance of a flat, skate-like boogie board. The latter attacks are more troubling, as those were likely more deliberate – the shark(s) followed through.

Question #4:

What is your overall scientific input on these incidences?

Dr. Cahoon:

One risk factor that needs to be considered is fishing activity. Struggling fish, as with one fighting on a hook, are powerful shark attractors. Again, they hear that noise, and the sound of a struggling fish is a dinner bell for sharks. I have had sharks hit fish I had on a line multiple times. I understand that at least one of the attacks at Oak Island was near a fishing pier – maybe not a coincidence. I think that swimmers should be cautioned to avoid areas where folks are catching fish (and that fishers should avoid swimmers as well). Once sharks hear that dinner bell, their behavior can change – they can become more aggressive.

Lawrence B. Cahoon, Professor
Biology and Marine Biology
University of N C Wilmington

http://uncw.edu/bio/faculty_cahoon.html

 

Comments

  1. What I fear the most is this may result in the CONTINUED useless killing of sharks along our waters…..

    As reported: “Shark killings exceed 100 million every year as humans become the predators. Many species may vanish in our lifetime, warn conservationists ahead of a critical meeting”. Per this article: http://www.theguardian.com/environment/2013/mar/02/shark-killings-humans-become-predators

    Sharks have been here for 100’s of millions of years. They are one of the oldest species on earth! They do not come out of the water and hunt us……we are in THEIR ENVIRONMENT when provoked…..please consider this!

    B Green Admin

    • Larry Cahoon says:

      Agreed. The vast majority of sharks (the ones still left) will never harm a human. They are important top carnivores in the sea. Ecological research shows quite clearly that removal of top carnivores has devastating effects on natural ecosystems.

Speak Your Mind

*