Migrations of Great White Sharks

**PanamaJack** · 19-05-2006, 16:11

Each year our Club - Sportfishing Club of the British Isles - publishes a magazine, and I'd been toying with the idea of putting together a brief note about research into their long range migrations for inclusion in it. Well it's done and, given all the speculation and general interest in Sharks in the General forum - well over 5000 'reads', I thought I'd also publish it here. Hope you find it of interest.
Dave

Great Whites are usually found in temperate offshore waters ranging from places like California, South Australia, Southern Africa & the East coast of the ‘States, and have most frequently been tracked around seal and sea lion colonies – these, together with tuna, appear to form the basis of their diet. And scientists have, for a long time, perceived them as creatures that hunt in a narrow band of coastal waters, rarely venturing far from shore.

But those theories have, over the last several years, been turned completely on their head given latest research using pop up, archival satellite tags. It appears they can be true ocean wanderers, swimming thousands of miles into the open ocean on mysterious migrations.

Firstly there’s the research conducted in 1999/2000 by scientists from the University of California in conjunction with those from Stamford University. They tagged six adult sharks as they fed near seal rookeries in California.

Initial data on the sharks' movements confirmed that they remained close to shore during the North American autumn, arriving at California seal habitats just as young elephant seals gather -- making them easy prey. And during this period, the tagged sharks rarely dove more than 90 feet below the surface and remained in temperate waters ranging between 50 and 57 degrees Fahrenheit.

However the surprise came in the winter, when four of the tagged sharks headed away from the coast.

One male shark migrated all the way from the Farrallones off San Francisco to near the Hawaiian island of Maui - where great whites have been rarely sighted - traveling at least 43 miles per day and remaining in the warm Hawaiian waters until the Spring. It then swam all the way back.

Three other tagged sharks migrated to subtropical waters in the eastern Pacific hundreds of miles west of Baja California, and then remained in the open ocean for months.

However there was more recent and extensive research undertaken in South Africa starting in 2003. Wildlife Conservation Society scientists, coupled with colleagues from the Marine and Coastal Management Department of South Africa & the White Shark Trust, as part of a major research project, tagged thirty two Great Whites. Interestingly they followed at least three different migration patterns, including wide-ranging coastal trips up and down the eastern side of South Africa. But the one of greatest interest was that of a female that the scientists nick-named Nicole, after Australian actress and white shark lover Nicole Kidman.

Any rate the epic saga started with Nicole being tagged on 7th November 2003. She then, after initially tracking south, turned purposely eastwards. And, during her journey, although she took frequent plunges to depths as great as 3,215 feet - a record for white sharks - while crossing the Indian Ocean, she spent most of her time swimming along the surface. Her course has led researchers to suspect that Great White sharks may use celestial cues for trans-oceanic navigation.

Then ninety-nine days after being tagged, as Nicole cruised a mile from the shore just south of the Exmouth Gulf in Western Australia, her tag detached and floated to the surface with all of her secrets. This leg of the journey alone - some 6,897 miles - was one for the record book. But when Nicole's distinctively notched dorsal fin was sighted again on August 20, 2004 back in Gansbaai, South Africa, this intrepid Great White had completed, in just less than nine months, a migration route covering more than 12,400 miles.

Latterly though Australian scientists having been tagging sharks in South Australia and identifying seasonal migrations that take them as far as southern Queensland and North-West Western Australia. North-Western Australia? The graphic on this web site - http://www.cmar.csiro.au/research/sh...movements.html - clearly shows them in the same area as Nicole. I know the sample sizes are minute but, I wonder, are they exploiting the same food source, or aggregating as part of their breeding cycle?

**PanamaJack** · 09-04-2009, 17:09

Whilst attempting to find some information on tagging programs for Porbeagle Sharks I came across this fascinating article - http://www.oar.noaa.gov/spotlite/arc...hiteshark.html - which describes two probable encounters between a manned research submersible at depths of 350 and 450 metres and a Great White Shark off the Hawaiian Islands. Certainly one of the Sharks appears to be heavily pregnant.

What particularly fascinates me though, and this was raised in my initial post on this subject, is what a mature fish that normally feeds on Seals, Porpoises and Whale carcasses what doing at those depths. Um ....

**Roddy Hays** · 10-06-2009, 08:58

What particularly fascinates me though, and this was raised in my initial post on this subject, is what a mature fish that normally feeds on Seals, Porpoises and Whale carcasses

Who says that's its "normal" diet, Dave ? I suspect it's the prey that is most often seen being eaten, but I think the vast majority if a GW's feed when not "on location" is primarily piscatorial. They eat tuna in quantity, bottom fish (especially rays and demersal species of shark), swordfish (just like mako), reef species of all sorts, and any other large prey items they can get their hands on - loggerhead turtles, for example.

A GW at depth (and I read that same article too some time ago) could be there for all sorts of reasons - look at the depths Nicole went to. Maybe it's something to do with some specific requirement for a heavily gravid female, some prey item in quantity, a need for specific temperature of water ? How about a factor related to mineral quantities in water at that depth, around those volcanic islands ?

I wonder if we will never know...............