Study Needs Divers, Snorkelers to Count Giant Sea Bass

Giant sea bass in a tank at the California Academy of Sciences in San Francisco | Photo: Caitlin Childs/Flickr/Creative Commons License

Are you a diver who explores the depths off the California coast? A team of researchers from UC Santa Barbara need your help to gauge the health of one of the state's most dramatic wildlife species.

Giant sea bass (Stereolepis gigas) were overfished so badly off the California coast over the 20th Century that the state's Department of Fish and Wildlife (then called "Fish and Game") banned all recreational and commercial fishing of the species in 1982. Since then, there's been some evidence that the long-lived, slow-reproducing species has been recovering, but no hard data.

That's where you come in. If you can get your swim fins in the water the week of August 1-7, the scientists behind that week's Great Giant Sea Bass Count want you to let them know how many giant sea bass you see while you're down -- even if that answer is "none at all."

The Count, being organized by UCSB biologists Milton Love and Douglas McCauley, is open to everyone from experienced divers to first-time snorkelers. "What's nice about this is that people can dive or snorkel anywhere -- reefs, wrecks, shallow water, harbors -- and for any duration, five minutes or an hour," said Love, an associate research biologist with UCSB's Marine Science Institute.

Before the bass' population took a serious nosedive in the 1980s, adult male fish in excess of six feet long and weighing more than 500 pounds weren't unheard of. Fish that size are a rarity now, which makes sense considering most of the giant sea bass population was probably born after 1982. Though they reach adulthood at 11 or 12 years of age when they weigh about 50 pounds, the truly gargantuan fish tend to be considerably older than that -- with estimated potential lifespans exceeding 75 years.

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Like many long-lived marine fish, the giant sea bass reproduces very slowly, with generations estimated at between seven and 10 years. That means it takes a long time to repair damage done to its population by overfishing. Once ranging from Humboldt Bay to the tip of Baja with a sizable population in the Sea of Cortez, the bass was pretty much wiped out in much of its range due to overfishing. The species is still essentially unprotected in the Sea of Cortez, and predictably, that means it's very rare there. The same is true of the historic northern populations: it's exceedingly rare to find giant sea bass north of Santa Barbara County.

But according to the International Union for the Conservation of Nature, which listed the bass as Critically Endangered in 1996, there has been sketchy evidence since 2004 or so that the fish may be recovering in Southern California waters. Which makes the Count a potentially important citizen science project, one that might help to fill in the gaps in our knowledge of what's happened to the bass since the 1990s.

In August, the adult giant sea bass that usually hang out in the depths come to shallower waters to spawn, often in the vicinity of the kelp beds where the juveniles hang out. That makes the week of the Great Giant Sea Bass Count an ideal time to spot the bass.

"We are hoping that this will act like an underwater version of the famous Audubon Society Christmas Bird Count, where reporting by citizen naturalists has helped scientists learn a great deal about the abundance and distribution of bird species," said McCauley, an assistant professor in UCSB's Department of Ecology, Evolution and Marine Biology. "So little is known about this rare but ecologically important fish species that we stand to learn a great deal from reporting efforts like this."

If you plan to dive or snorkel between August 1 and 7, you can get more information on how to report your sightings (or lack thereof) on the Count's Facebook page. When all the reports are collected, Love and McCauley will work with researchers from Cal State Northridge to compile the data and attempt to make some sense out of it.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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