White sharks in Hawaii

Our article Occurrence of white sharks (Carcharodon carcharias) in Hawaiian waters as well as supplementary information appears in the Journal of Marine Biology. Many thanks to the divers, fishermen, tour operators and researchers who provided information.



Locations of white sharks recorded around the Main Hawaiian Islands, 1926-2012


White sharks were known to the Hawaiians before contact with Europeans. There are pre-contact artifacts containing white shark teeth as documented by Leighton Taylor. In modern times white sharks have been sighted occasionally around the Hawaiian Islands, as documented in our paper. Our findings are surprising in that they do not fit the pattern of seasonal migration that we see from the satellite tracking data. However, they fit very well with recently published information about multi-year migratory patterns of sharks tagging off the coast of Mexico. Michael Domeier and Nicole Nasby-Lucas just published findings of mature females spending over a year offshore, presumably during gestation. Such animals could be sighted around Hawaii during any month of the year.


When reporting the occurrence of animals such as white sharks, it is critical that species are identified correctly. Many reports that have appeared in the news and other popular media are incorrect. Scientists use very specific morphological criteria to identify species, such as the shape of teeth or bones, the exact dimensions of various body parts, or the ratio of one body dimension to another.


White sharks are easy to confuse with other closely related species such as shortfin mako sharks and salmon sharks. Shortfin mako sharks occur regularly in Hawaii, and can be distinguished from white sharks by differences in body form, but these measurements can be difficult to make without good quality photographs taken with a side view. Details on these characters are available from guides such as Leonard Compagno’s FAO volume.


In situations where side-view photographs of the animal are not obtained, but good images of the head are taken, it is possible to use the shape to distinguish white and mako sharks.  A large shark video taped near Kaena Point, Oahu in January 2012 was misidentified as a white shark by the news media (http://www.hawaiinewsnow.com/story/16510766/great-white-shark-spotted-off-oahu) and erroneously re-reported as a white shark by many other news outlets. Our morphometric tests show that the individual was a mako shark, and other experts in shark biology who viewed video and still images agreed.



How can you tell a white shark from a mako shark?


It is very easy to confuse related species. Scientists use a variety of morphometric methods to distinguish species, but the information required for these determinations may not be obtained from sightings or photographs. Read a field guide such as


Leonard J.V. Compagno, 2002, SHARKS OF THE WORLD, FAO Species Catalogue for Fishery Purposes No. 1, Vol. 2




Dr. Compagno’s book will reveal a number of key features that might be visible.



The distance between the pectoral fin and the dorsal fin is greater in the shortfin mako shark.




The white shark’s head is blunter, whereas the shortfin mako shark’s head is sharper.




The teeth of the shortfin mako shark are long and slender, without serrations. The teeth of the white shark are triangular and have serrations.


If photographs can be obtained of any of these features, species identification may be possible. For instance, the shark sighted at Kaena Point, Oahu in January 2012 was filmed by Dominic Gaballo, revealing an acute head shape.



The shark sighted near Kaena Point in January 2012 had a long, acute snout. This and other features indicated that the animal was a shortfin mako shark.

 
 
 



oceanography department

pelagic fisheries research program

university of hawaii at manoa

honolulu, hi 96822 usa

808.956.4109





copyright 2013 kevin weng