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Año Nuevo Island White Shark Study
The Lure as a Tool for Studying White Sharks

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Año Nuevo Island

A white shark is a very alert and visual predator with a well known sense of smell.

Traditionally white sharks have been lured to boats by ‘chumming’ them up while at anchor. Chumming is a rather nebulous term but it’s basically the practice of attracting the shark to an artificial food source and then holding that shark’s attention there after by feeding it. This practice started in S. Australia during the 50’ and 60’s during the dawning of the ‘Cage Age’.

Historically everything from whale meat to horse meat was utilized by cage diving pioneers with the staple evolving into a more restrained present day combination of mostly tuna, shark or other mostly fish based chums along with the odd secret recipe or ingredient added in here and there; nothing beats a dead whale as a baiting station.

Contrary to popular belief, sharks have no aversions to the scent of other dead sharks.

The initial attraction process used by sport divers world-wide is almost always followed with the feeding of the attracted animal in order to hold its attention and/or bring it into contact with the client viewer.

This is a proven and reliable method for attracting and manipulating white sharks by sport divers and is still the principle operating procedure on the southern coasts of Australia and Africa and more recently near Isla Guadalupe of the Californian coast.

More recently beginning in the early 90’s, researchers with UC Davis and the Point Reyes Bird Observatory innovated the use of surfboards as a lure to acquire ID images; other shapes were examined as well and researchers were able to gather significant amount of information and understanding through this effort.

South Africa in the meanwhile has also been innovative with the use of lures, most notably by Chris Fallows and crew; however the traditional chumming methods are still the primary mode of attraction, especially sport-divers.

The Pelagic Shark Research Foundation began studying white sharks at Año Nuevo Island, California in 1992.

Since we weren’t interested in cage diving with these sharks or catering to tourists, we departed from the traditional method and decided to employ a different strategy for strictly research purposes.

We developed a simple system involving a small drifting boat, a small portion of natural bait and prey shaped lures.

Natural bait in this instance refers to a relatively fresh 15-20lb portion of marine mammal blubber; while tuna or fish is not ‘un-natural’, it is not what the sharks are preying upon at our particular site at Año Nuevo Island.

The marine mammal tissue is exactly what the sharks are there to feed upon and that is what we use to attract them. We never feed them; excepting when we fed them two baited transmitters during the 1998-99 seasons.

Rather than use a surfboard as is used at the Farallones, we went a step further and sawed out plywood seal shapes for use as a shark lure.

Most of the shark predations we observe at Año Nuevo Island involve large sub-adult and adult seals so we chose a shape exactly 8’ long in the shape of a young adult female e-seal. At 95 inches long (234 cm) the lure also serves nicely as a length measure for gathering info once a shark has made contact with the lure.

The lure is painted brownish gray on the down-side and yellow on the top-side; the yellow is strictly for the visual benefit of the researchers,making it easier to keep an eye on.

The craft:
It’s a simple process that begins by going to the seal colony and attaching the flat seal lure to a medium-heavy tackle, sportfishing- tuna rod; I like the ‘Ugly Stick’ and Penn 6/0 and 80 lb test combo with Gamgatsu barrel swivel and snap.

We quietly motor in near the rocky haul outs and landing areas used by the seals and set tackle and then line up the lure for deployment.

Position is everything; before we begin a drift we calculate wind, tide and current as well paying close attention to the marine mammals and birds whose behaviors can be discerned to indicate shark presence or activity. During winter, 20’ foot swells are not uncommon and we often have to work further from shore.

Once the lure is deployed off the stern, the boat is motored a short distance away.

Once the lure is in position the boat is put into neutral/full-stop and the engines turned off.

When the boat and lure are in position the bait (15 lb seal blubber) is put into the water and the experiment begins.

The sample itself is typically 4-6 hours per day in duration and we try to cover every single day from October through January with periodic visits into February.

At the starting point of every sample drift, the time, GPS/GIS position, water depth and temperature are recorded on a note pad. As the winter weather kicks in the work becomes more difficult. October is typically best and by December the there are many storms coming through that often only allows us o go out a few day per week. We get out as often as the weather allows, typically a season will account for 40-60 days of the Oct thru Jan.

Once the conditions have been assessed and the boat/lure is positioned and drifting; the research team prepares for contact by getting the camera and tagging equipment ready. There are many variables to factor in as a photographer, water clarity and ambient light being the primary consideration. Both topside and subsurface photo/video documentation is crucial to the study in terms of individual ID and sex categorization as well as behaviors. Callaghan Fritz-Cope assembling an underwater housing for digital video-camera.

For documenting the subsurface action we utilize a housed digital vid-cam (VX2000) mounted on a light-weight alloy boom that is both stable and wieldy; Both top-side and subsurface actions are recorded with digital cameras. SLR cameras are also used on a back-up basis.

It can take anywhere from less than a minute to several hours to detect the presence of a shark and they don’t always stay around for very long; the presence can be as subtle as a point of turbulence in the water or as obvious as a large sharks face at the lure, rarely, they will strike the lure in a breach hit or actually bite the lure into pieces. Typically the contact is cautious and brief.

Once a shark has been detected; the alarm is raised, data noted and the first order of priority is to get an ID image; the lure is carefully reeled in across the surface in hopes of interesting the shark to further investigate, thus allowing clear ID images of the animal to be taken. Motion on a lure will often re-motivate an otherwise reticent shark to take interest in the lure.

As well, by drawing the lure in towards the boat, the shark may be brought within striking range of the tagging and biopsy lances. A tale tell turbulence appears behind the moving lure.

Once the lure is drawn in; the shark will often enough present itself within reach of a tagging lance and the underwater camera.

When drawn in close, the underwater camera can document the sex of each shark encountered.

above: male shark

above: gravid (pregnant) female

Utilizing this system we are able to operate underwater perfectly well without the need of a cage.

Occasionally a shark will take a brief interest in the metallic, zinc and electro properties of the boats out-drive and stern area; the bait is always kept from the shark’s grasp and is never directly presented to the shark. A close watch is made on an approaching shark at all times; if a shark appears to be intending to make contact with the boat; the handle end of the lance is used to fend and guide the sharks from making any direct contact with the boat. Overall the sharks are very manageable although absolute and complete caution should be used at all times as they can be unpredictable, explosive and volatile. In over a decade of operations at Año Nuevo Island the PSRF has maintained a perfect safety record.

In the image below; C. Fritz-Copes tends to ‘Deca’, shark #010.

Whenever possible the sharks are carefully tagged on the dorsal saddle with yellow ID tags, unless already tagged. In addition to the ID tags we are periodically attaching satellite archival transmitters or “smart-tags”.

ID tagged sharks are a priority for attachment of Satellite transmitters because the animals are already logged in to the existing data base.

These tags record data internally and store the information until such time that the device is programmed to automatically detach itself from the shark and float to the surface. Once at the surface the transmitter uploads all the stored data to orbiting satellites which in turn down-load that information to land based computers. It makes the science easy and unlocks mysteries that have puzzled us for long-time. The transmitter records and later reports data on two hour intervals (algorithms) in regards to depth, temperature and position and other information. The satellites transmitters were designed by Paul Howie of Microwave telemetry.

By using this system we are able to mark, count and identify individual sharks and fit them into generational and sex categories; this allows us to gather information on population dynamics and abundances The lures are also interesting in regards to observing how the shark go about handling and investigating the lures.

With the use of cutting edge satellite and acoustic telemetry we are mapping out the white sharks movements and range; so far our sharks have shown a tendency to arrive from the open ocean in Fall and patrol around the Eastern Pacific pinniped colonies and begin to depart offshore during December-February.

Off shore the sharks are traveling over 50 km per day and spend most of their time at depths ranging from 300 to 700 meters deep in surprisingly cool temps- not a lot of nocturnal/diurnal patterns are apparent to us thus far.

We have deployed 11 acoustic transmitters and 7 satellite transmitters thus far in addition to the ID tags.

Similar studies are being conducted at the S.E. Farallon Islands by the PRBO researchers Scott Anderson and Peter Pyle; another team working for Michael L. Domeier of the Pfleger Institute of Environmental Research has been very successful in pioneering a white shark research project at Isla Guadalupe.

Domeier’s team has placed dozens of satellite transmitters and have had numerous re-sights of those animals while working up there.

The next few seasons should be very productive in terms of answering many questions about the mysterious C. carcharias of the Eastern Pacific.

Always bring a pen, or something to write with:

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