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Merit McCrea – WHEELHOUSE SCOOP

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Thursday, June 13, 2019
Big bluefin bite!
Wednesday, July 10, 2019
Excalibur


500 giant seabass
So... it turns out, if one snoops around much trying to find out how many giant, or black seabass there are you'll find out "scientists have discovered there are only about 500 of the critically endangered giant sea bass, total." Now, if you've been out much at all fishing in SoCal, or diving much, this claim is absolutely unbelievable. In fact, it seems it simply adds evidence to the theory marine scientists are simply out of touch. Or worse yet, they're pursuing agendas, saying what gets them funding and fame and "peer reviewed science" is a bunch of bull. But the truth almost always turns out to be, some advocacy group has misrepresented real results and the scientific community is above taking issue with it.

I was mildly curious about the ridiculous 500 fish thing and so did some snooping. I found that was exactly what was being claimed. L.A. Times reporter Louis Sahagun wrote, "The breeding population of the giant sea bass — which is listed as critically endangered by the International Union for Conservation of Nature — is believed to be only about 500 individuals."


The Long Beach Post quoted Dr. Douglas McCauley (UCSB, MSI) as having said, "One study using genetics estimated the effective population size (number of mature breeding adults) of giant sea bass in the wild at 500, according to McCauley, although that number is very imprecise."


McCauley said it right while the Post author interpreted it wrong. It's not the "number of mature breeding adults." It can be close, or way under it.


Futurity.org said, "A recent genetic study suggests that fewer than 500 breeding giant sea bass may exist in California." The Wikipedia article on GSBs says, "The total breeding population in 2018 is estimated to be around 500 individuals, of which 40 to 50 return to spawn around Catalina Island each year."


Animaldiversity.org was right down the line following the actual science, without bias. In fact it turned out most online sources of population info tended to follow a realistic "We don't know, but it seems like there are more of them finally," perspective.


As for the DFW, they say "Anecdotal information suggests there has been a gradual increase in giant sea bass numbers over the past few years... No scientific research has been conducted on giant sea bass population trends. To date there is still relatively little known of this apex predatory fish."


The Channel Islands National Marine Sanctuary also refrained from claiming the GSB population as just 500 reproductive fish, instead following the obvious trend for increasing observations.


Most said the population had reached a very low but unknown level by the 1960s and '70s. Although they've been off limits for sport anglers and from directed commercial take since 1982, it wasn't until the banning of gill nets from coastal state waters and within 1 mile of offshore islands in 1994 via the 1990 passage of proposition 132, that their population began to show an apparent, slow but increasing recovery.


Current regulations still allow gill netters to retain and sell one per trip. Sport angers fishing Mexican waters are allowed to bring up to 2 per trip into California. Mexico has no restriction other than regular limits.


So, what prompted certain, mostly non-scientific sources to cite a population of just 500 fish, total, while a majority of sources spanning agencies, fishing and diving sources and marine science seemed to maintain a more believable perspective?


The source of this bad info seems to stem from a deliberate misinterpretation of the results of a genetic diversity study published in the journal Fisheries Research, December 2015: "Low contemporary effective population size detected in the critically endangered giant sea bass, Stereolepis gigas, due to fisheries overexploitation" (Chris L. Chabot et al.).


The paper's finding is the "effective population" of GSBs is about 500. However, effective population is a genetics term relating to genetic diversity, not population size. And its primary implication is that at one time in the past hundred generations or so, there were very few of the species.


When a population size stays the same for thousands of generations is when the effective population size comes nearest to the actual population number. Examples seem to point to it being, at most, about 70 percent of the true population size, and averaging just 34 percent of it. This, incidentally, not only varies by which part of the genome is used for analysis, but can be in the context of only one sex.


If a population has recently been very small, then rebounds to huge numbers, the resulting population can be so closely related to one another it retains the genetic effective population of whatever it was during the low population time.


Within the DNA's code is lots of stuff that rarely comes out — gathered over eons of evolution and saved for a rainy day when a species needs it. Changes to genes happen very, very slowly, but changes in their expression or use can happen in just a few generations.


Rarely used code can be selected for use by a change in the environment or deliberate breeding. The few individuals born that happen to employ it become the survivors and breeders.


Think of it as all dog breeds having all the genes required to be any breed. But from breed to breed the difference is which plan is used — short legs or long, big or small, grumpy or sweet, mean or caring.


But the big eco-worry is when a population hits a bottleneck or becomes really small, some of the code that was present in the species becomes lost. The species isn't able to adapt as well as it once was. That's why "effective population" size is a concern worthy of doing the genetic analyses required to estimate it.


Ecologically it says, recovering a species is great, but it's not the same as avoiding such bottlenecks in the first place. Some damage has been done. This study points to GSBs having come close enough in the '60s and '70s for conjecture.


Bottom line? It's mostly biased non scientists who omit important details, take science and deliberately misinterpret it — in this case lying to the public by implying only 500 black sea bass remain in the wild. And they do it to create evidence supporting an agenda, e.g. "fishermen are not conservationists." The fishing public's resulting distrust of marine science is collateral damage. "Scientists estimate there are just 500 black sea bass total including Mexico and SoCal! Really?! Ha!"


* * *


Merit McCrea is saltwater editor for Western Outdoor News. A veteran Southern California partyboat captain, he is a marine research scientist with the Love Lab at the University of California at Santa Barbara’s Marine Science Institute. He can be reached at: merit@wonews.com.


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