White Shark (Carcharodon carcharias) photo: Howard Hall
The two main focus areas of PRBO's White Shark Research at the Farallon Islands in the past included Individual Shark Identification and Shark Watch and Population Monitoring. Currently, PRBO is only continuing the Shark Watch and Population Monitoring Project.
More on this issue as published in PRBO's Observer 131, page 8
Notes of interest:
Shark Watch and Population Monitoring
photo by P. Pyle
In 1987 PRBO biologists began documenting and observing shark attacks from atop the island at the Farallon lighthouse. Here is a paragraph from an article that appeared in PRBO's Observer in 1992.
Successful biological inquiry requires a healthy combination of both focused technical research and ample field observation of a subject species. Turning our attention to the latter, we standardized and expanded our observation program in 1987 by stationing one to two observers at the lighthouse during all daylight hours in fall, specifically to search for shark activity. Initiated by Scot Anderson, the shark watch has now produced five years of fall surveillance. During this time we have witnessed 40-60 predatory events per year, an increase from a previous maximum of twelve in 1986. By standardizing our observations, we can determine whether this perceived increase in shark activity is real or simply the artifact of enhanced observer awareness at Southeast Farallon Island It will also enable us to compare the occurrence of attacks with oceanic conditions, such as temperature, salinity, and clarity, which show wide inter-annual variation in the vicinity of the Farallones. Preliminary analyses suggest, for example, that attack frequency increases with colder sea surface temperatures in fall, disputing a widely believed theory that warmer waters (such as those associated with El Nino) bring more sharks into our region. Our findings also suggest that white shark attacks are positively correlated with water turbidity: perhaps the lack of visibility impairs the ability of pinnipeds to detect and escape the sharks. As both colder water and higher turbidity result from coastal upwelling, though, one or both of these correlations may be coincidental. We will soon perform multivariate analyses to see which oceanic conditions have the greatest effect on shark behavior.
Using a standardized method, biologists continue to monitor shark attacks, recording frequency and location. This provides us with information on environmental effects, population trends, and behavior patterns of prey and predator.
One of the goals of our research is to minimize shark/human attacks. Here are some suggestions that may help to prevent shark attacks on humans. (these are speculations based on our research and observations of shark/human encounters):
|TIPS FOR SURFERS TO AVOID BEING CHOMPED|
1. Avoid rocky drop-offs beyond break. (e.g. Davenport, Salmon Creek)
2. Stay in water < 20’ deep (sharks prefer hunting in 20-90' depths)
3. Avoid areas near pinniped haul-outs (Año Nuevo, Jenner)
4. Look for large boils (not wave/rock related) caused by the sharks powerful
5. Pay attention to spooked feelings (we may have a 6th sense about sharks)
6. Wear a pin-striped wetsuit (i.e., look as little like a seal as possible)
7. Surf with a buddy
Environmental Factors Affecting the Occurrence and Behavior of White Sharks at the Farallon Islands, California (Adobe.pdf)
Trends in White Shark Predation at the South Farallon Islands, 1968-1993 (Adobe.pdf)
(These two papers are from the book Great White Shark, written by Klimley and Ainley, 1996, Academic Press).
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