The Dorsal Fin

The Gulf of the Farallones National Marine Sanctuary has recently posted a draft environmental assessment to analyze the impacts of issuing a permit to Dr. Michael Domeier of the Marine Conservation Science Institute, which would allow the tagging of 11 additional great white sharks (3 males, and 8 females) within the marine sanctuary, using the catch and release method that has been featured on National Georgraphic’s Expedition Great White.

Dr. Domeier was issued a 1-year permit in September of 2009. During the 2009 white shark season, he and his team used the catch and release method to tag 2 male white sharks at the Farallones. However, a bit of controversy stirred up when one the tagged sharks was hooked in the esophagus, and the circle hook had to be cut and left in the shark. According to the draft environmental assessment, “the public and members of the other research teams studying white sharks in the region were concerned that the shark had died and that the tagging was being conducted primarily for a National Geographic television program.”

It should be noted that the hooked shark made its normal migration pattern after the incident, according to data supplied from the tag, and that the tag was still reporting normal data 8 months after it was hooked. (see Southern Fried Science’s interview with Dr. Domeier)

Supporters of Dr. Domeier’s SPOT tagging methods argue that this research provides invaluable data, which cannot be gathered using other methods, and that the data could be beneficial to the species. Those who oppose these tagging methods argue that the potential gains simply do not outweigh the risks.

Regardless of which side of the fence you might be on, if you have genuine interest in this topic and are willing to read the environmental assessment draft, the GFMNS is open to your comments. Comments should be submitted to Carliane.Johnson@noaa.gov until October 12, 2010.

The video above from NatGeoTV.com presents a theory that a killer whale from the L.A. Pod of orcas might have used tonic immobility during a 1997 attack on a great white shark at the Farallones. The theory suggests that the orca (identified as “CA2″) potentially rammed the unsuspecting white shark, stunning it. While the shark was still disoriented the orca could have either grabbed the great white while it was on its back or flipped it over. The orca could have then held the shark upside down in its jaws, keeping it in a state of tonic immobility until the shark drowned.

While there is no hard evidence or clear-cut video footage of orcas inducing tonic on sharks in the NatGeo feature, the video does include video evidence of killer whales attacking stingrays in New Zealand using a similar technique. As seen in the footage, the killer whales approach the rays upside and grab them with their mouths, then right themselves, so that the rays are upside-down and effectively immobilized. Researchers hypothesize that if orcas have learned to use this technique on rays, then it’s not far-fetched to assume they could use a similar technique on sharks.

On a side note, some of the underwater footage of the “great white shark” in this clip features a shark that is clearly not a white shark. While I admittedly am not great at identifying certain species of sharks, I’m guessing the footage features either a lemon shark or a bull shark. Anybody care to enlighten me on the species seen at around 3 minutes in?

Thanks to DeepSeaNews.com for the video find.

An incident which occurred at the Farallon Islands, on October 4, 1997, involving an orca attack on a white shark has somehow become “news” this weekend, at least on the ABC News website. The incident which was documented on video (and has been available on YouTube for years) is currently being featured on National Geographic Channel’s Wild series in an episode titled “The Whale That Ate Jaws.”

I have no idea why this story is back in the news this weekend (except for the fact that there’s a NatGeo show about it), although it is an interesting story, nonetheless. Also of interest was the resultant observed behavior of white sharks around the Farallon Islands after the predation occurred. According to a National Wildlife Magazine article the white sharks typically found around the Farallon Islands from September to December simply “vanished” after the orca attack on the white shark. The sharks did not return until the next fall. For a more in-depth discussion of the October 1997 event, as well as information about the “L.A. pod” of orcas and a possible second orca attack in 2000, check out the Showdown at Sea from National Wildlife Magazine.