Dive Dry with Dr. Bill

#580: "Bombs" ad Basses

It has been over a year since I've written about one of my favorite "denizens of the deep." Two years ago I observed and filmed over 200 of them, but last year I only had four brief sightings. Of course part of the reason was that I did most of my summer and early fall dives at night, but friends tell me I should look up or out more than I do! I'm referring to our incredible giant sea bass, Stereolepis gigas. Yep, the huge fish I refer to as the "gentle giants."

Back in the late 1800s, these fish were referred to as "jewfish" although the name was later changed to "black sea bass" (even though they often aren't) and then to "giant sea bass" (which the adults certainly are). Many felt the name "jewfish" was politically incorrect in view of any possible negative connotations toward members of the Jewish faith. I did some research recently that gives an interesting spin on this older name. Back in 1697 famed explorer William Dampier visited Jamaica and discovered that those of the Jewish faith there favored the "jewfish." According to the Oxford English Dictionary, the name was used because it was the largest kosher fish in the area since "it hath Scales and Fins, therefore a clean Fish, according to the Levitical Law." So much for political correctness.. at least in this case.

The giant sea bass will soon be returning to our local waters to court and mate, so I thought I'd get a head start in providing information about them for my readers. The trigger for this column was an e-mail from Dr. Larry Allen, chairman of the biology department at Cal State Northridge and a noted fish expert. He mentioned he was continuing some studies on this species done by Dr. Michael Domeier when he worked for the Pfleger Institute of Environmental Research (PIER), and was interested in buying my DVDs on the gentle giants. Several of his students have been in contact with me about their focus in these studies.

Years ago Domeier had moved his attention to great white sharks and in 2005 I had the pleasure of going on an expedition to Guadalupe Island funded by PIER to film and tag them. The methods used to dart tag them back then were relatively non-invasive. Domeier went on to work with Chris Fischer and the OCearch team which employ methods I feel are far too invasive and harmful to the great whites. By capturing them using large hooks, hauling them out of the water onto a modified swim step and then bolting a SPOT tag to their dorsal fin; the team formerly referred to as "Shark Men" on the National Geographic channel have caused injury to these fish in their efforts to trace their routes through the world's oceans. But that's another story...

Since I've never been all about making a buck, I suggested Dr. Allen and his students look at my videos for free on my YouTube channel (drbillbushing). Yep... FREE! I may not offer you a free lunch, but you can look at most of my videos there without spending a penny. I told him I also had lots of high definition footage of the giant sea bass from when I filmed with a crew from Japan for a documentary that aired on NHK, that country's public TV station in the fall of 2012. Hopefully the English version of that documentary will eventually be available on the Discovery Channel or BBC.

Larry sent me a paper he had recently published on methods employed to age giant sea bass. This has been a question of interest to me and to many of the divers and non-divers who ask about these behemoths. Fish are usually aged using bones located in the ear called otoliths. These bones exhibit growth rings similar to those found on trees and, if they are available, can give us a good guess about their age. The problem is that when the fish were more plentiful in decades past, the heads were often chopped off and discarded (at least by the commercial fishers). Thus the otoliths were not available to conduct aging studies. In addition, the viscera ("guts") were also discarded so there were few analyses of their stomach contents to understand their ecological role.

Dr. Allen's paper described a new method of aging fish that I was unaware of and thought it was of sufficient interest to share with my readers. It is called bomb radiocarbon dating. Those of you old enough to remember atmospheric testing of atomic weapons during the 1950s and 1960s are probably familiar with the documented increases in radiation levels on land, and specifically in milk. This same atmospheric radiation also fell out onto the world's oceans and created a baseline level of carbon-14 that could be measured in coral, bones and calcified structures. The date of this rise was about 1958-1959.

Fortunately I have a valid birth certificate so I'm painfully aware of my own age. However, fish do not so their birthdates and longevity are mysteries that science wishes to solve. Previous estimates of the longevity of the gentle giants ranged from 75 to over 100 years, but these were based on limited data and poorly documented methods. With the technique of otolith rings and bomb radiocarbon dating, this mystery can now be solved.

Of course giant sea bass are now a protected species in California so capturing them even for scientific purposes is generally forbidden. However incidental catch by commercial fishers does occasionally result in a gentle giant being landed in port. In January of 2010 one such specimen was unintentionally caught off Santa Cruz Island and brought in to Santa Barbara. Its undressed weight (you don't step on the scales fully clothed do you?) was estimated at 500 lbs and it was 7 ft long. Using otolith ring counts the age was estimated at 62 years (just old enough to collect Social Security).

Using the radiocarbon method, age could only be determined at greater than 50 years since the fish's birth pre-dated atmospheric testing. However, this method will be very useful in aging fish in the apparent recovery of this species since most will be younger than the baseline year.

So it is currently difficult to say for sure how long a giant sea bass may live. Based on these well-documented techniques, it will be possible to age future specimens caught incidentally. However, this is still a highly invasive method so it is out of the question for this protected species except on that basis. I asked Dr. Allen about using fin spines, portions of which could be taken without serious injury to the fish, but in older fish they do not have well-defined annual growth rings. Now that I know for sure those 7 ft and 500 lb giants are senior citizens, I'll surely show them respect!

© 2014 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Head of giant sea bass (GSB) and GSB hovering near kelp;
courting pair and mating aggregation at Blue Car Wreck dive site. .

This document maintained by Dr. Bill Bushing.
Material and images © 2014 Star Thrower Educational Multimedia