Shark encounters in Hawaii – look out October

9Oct2015, another shark attack, non-fatal but with a violent and painful outcome, an encounter between surfer and niuhi, the man-eater who hunts, kills, and eats in the deeps and shallows around Hawaii’s islands.

The State of Hawaii DLNR has an excellent, maybe the definitive Hawaii Shark website with statistics,  Lots of information here and a must read if you are serious about learning about the man in the brown suit.  All information here is courtesy of Division of Aquatic Resources, Hawaii Department of Land and Natural Resources.

The graphics on this site are interesting … http://dlnr.hawaii.gov/sharks/shark-incidents/incident-graphs/  .  When you remove the spikes there is a periodicity of about 10 years … hmmm.  We’re a couple of years past the peak.  Also eyeball smoothing will show an upward trend over a 30+ year period.  Is there a sunspot correlation ? Well I dunno.

sharkincidentbyyear

There’s no correlation between incidents and people in the water in the DLNR graph (below).  This graph addresses often quoted speculation that the more people in the water, the greater the incidence of attack, This implies that people expose themselves to a constant and natural risk and the incident is a function of the number of people in the water.  The graph below does not support this notion,  but the may not be valid anyway if the number of people in the water  is biased towards non-sharky waters (e.g. in Waikiki or Hanauma Bay).  In other words, scads of tourists sitting in the water in Waikiki may indeed have zero correlation with shark attacks , because sharks don’t frequent protected inner reefs of Waikiki.

The presence of surfers, swimmers or water sportspersons on the other hand and the location … also known as the shark habitat – may radically increase the odds of attack since the human activity intersects the danger zone of shark predation.  What is that zone?  Good question.

incidents bypeople

sharkincidentbymonth

Monthly trend … maybe an Oct Nov peak …  There may be tighter correlation between short term weather events and shark attack (e.g. murky water) that is masked in the crude stat here.  The web commentary– ” The relationship between number of people in the water and number of shark bites is not always as expected. There appears to be an increased risk of being bitten by a shark during certain months, in particular October through December. Early Hawaiians recognized this, and cautioned against going in the water at that time. Although fewer people are in the water from Nov-Dec, some of Hawaii’s most serious shark attacks took place during those months. Analysis of weather/ocean conditions and tiger shark life history is beginning to shed some light on the patterns shown in this graph.”

It would be interesting to see a long monthly time series of incident vrs monthly regional rainfall , or a rainfall index that would contain that information …  to paraphrase, there may be specific weather/ocean  condition / shark life history data that are more tightly correlated with shark encounters of the violent kind.  In particular there is speculation of the linkage between high stream runoff and shark attack that warrants study.  Maybe there’s no correlation but data and analysis may tease this out.

What does not come out in the graphics on the website is information about the common elements of shark attacks.   Locational clusters, shark habitat characteristic may still remain to be derived from the data on the DLNR website.

In summary, the DLNR has a fine product here which is a great foundation for becoming informed about this interesting and scary area for Hawaii and our ocean oriented life-styles.

Oh yes, the recent news  which prompted this entry: 2015/10/9  1025   Oahu, Shark attack at Leftovers between Laniakea and Waimea, 10-12 foot shark – unknown or unreported type, loss of left leg. depth unknown or unreported, but in the surf zone.  I wish a speedy recovery to surfer Colin Cook and heartfelt condolences for his radical injury.  Good job fellow surfers and folks who helped, for doing what you did to help this man survive!

Data from DLNR…

Notes:

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