Sevengill shark sightings are on the rise off San Diego, and citizen-science divers who have been logging their close encounters are now looking for a biologist to help explain why the sharks have become more common off the coast since 2009.
In particular, they hope to find a scientist who will be able to help them ID individual sharks in their photographic and video database. That database currently has more than 130 photos and about 50 videos of the shark in local waters, and these, along with other information, have been uploaded to a global citizen-science Shark Observation Network.
“We are looking for any shark researcher who is willing to donate some free time outside their normal research to assist us with the ‘hard science’ part of the project, namely, running our photographic database through a pattern-recognition algorithm, which we can provide, and analyze the data,” said Michael Bear, a shark enthusiast and AAUS (American Academy of Underwater Sciences) Science Diver with more than 1,000 cold-water dives in California.
Bear, also a columnist for California Diver Magazine, is the brains, heart and legs for the sevengill sightings citizen-science project. He recently contacted California Sea Grant about potential collaborations with our statewide network of researchers and coastal specialists, hence this blog. We hope to help him find a generous soul who knows how to use spot-recognition software and can apply it to sharks.
The idea is to use the freckled markings on the sharks (see panel below) to ID and track animals, who might be returning to an area year after year, or who may be new residents to local waters, Bear explained. The approach is based on the ECOCEAN whale shark photo-ID library, which is being used to study and protect “the world’s largest fish.”
“There are no deadlines or pressure to publish results any time soon,” Bear said. (There is also no recompense.) “If a researcher is willing, down the road, to assist in applying for a grant, that would be welcome, but not mandatory.”
The sevengill shark is among the last living members of a group of sharks distinguished by their seven gill slits. Most sharks have five, or less frequently, six.
The large, slow-swimming species feeds on seals, dolphins, skates, fishes and carrion and can reach lengths of 3 meters. Its lifespan is estimated at about 50 years.
Sevengill sharks were overfished off California in the 1930s and 1940s and, up until recently, their core haunts (their pupping and nursery grounds) were believed to be in Humboldt and San Francisco bays.
The species, known in scientific circles as Notorynchus cepedianus, is found in temperate coastal waters around the world and is listed as “lower risk/near threatened” in the eastern Pacific on the IUCN Red List of Threatened Species.
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