Guest Post by Willis Eschenbach
Well, after my last post, The Solution To Dissolution, I thought I was done with the Dungeness crab question. And I was happy to be done with those chilly crustaceans. Writing that post brought back memories of how cold the fishery is. I remember leaving out from Eureka harbor at the north end of California and crossing the bar at the mouth of Humboldt Bay well before dawn. The “bar” is where the sand piles up at a harbor entrance and it gets shallow enough for the waves to break … and Humboldt Bay has a bad bar. Lots of people have lost their lives there. Here’s a Coast Guard boat fighting its way out to sea across that bar …
On the way out to the fishing grounds, we had to make up the bait bags for the crab pots. We used frozen anchovies for bait, and I can assure you that breaking up blocks of frozen fish before dawn with my hands in thin rubber gloves in pitching seas in December is not my idea of a good party … I’m a tropical boy whose idea of frozen things relates more to whiskey glasses and drinks with tiny umbrellas and the like. So I’d hoped that my last post would let me return in memory to warmer times and more pleasant fisheries.
In that post, I discussed the manifold problems with the incorrect media claim that “The Pacific Ocean is becoming so acidic it is starting to dissolve the shells of a key species of crab, according to a new US study.”
I pointed out that the ocean was moving a bit toward neutral, a process that alarmist scientists and the media falsely call “ACIDIFICATION!!!” I noted that terminology was chosen to scare people. I said that if we used the correct terminology, the media claim would be:
“The Pacific Ocean is becoming so neutral it is starting to dissolve the shells of a key species of crab, according to a new US study.”
And of course, that is both not alarming and not possible.
So with that post, I figured my crabby memories were in the rear-view mirror.
But noooo … as Michael Corleone said, “Just when I thought I was out, they pull me back in!” Over on Facebook someone mentioned that I hadn’t looked at the most basic data—how many crabs were actually caught, and were the numbers dropping? And they were right, it’s a very valid question.
However, this question is not as simple as it seems. Changes in fishing regulations, changes in season length, changes in the number of boats, things like excess domoic acid making the crabs poisonous and delaying the season openings, all of these kinds of issues can influence the total landings of any marine species.
Plus the information is kind of hard to find. I did find this, from the Monterey Bay Aquarium Research Institute, clearly the most confusingly crabby chart imaginable.
Finally, I thought “The UN Food and Agriculture Organization must have the data”, and they did. So with the above caveats about changes in regulations and seasons and the like, here are the records from the FAO FIGIS Fisheries Statistics regarding Dungeness crab landings for the Northwestern US including Alaska, and for Canada.
Figure 1. Total Dungeness crab landings, US and Canada. The big drop in 2015 was from excess domoic acid in the crabs greatly delaying the opening of the Dungeness crab commercial fishing season. The background shows crab fishing boats leaving out of Newport Harbor in Oregon.
There are several interesting things about Figure 1.
First, CO2 has been rising, and the oceans have been becoming slightly more neutral, during the entire period shown above.
Next, if the Dungeness crabs are getting dissolved by the slight decrease in pH, they didn’t get the memo …
Next, in my previous post I’d described a problem with the study, which used samples collected in 2016, as follows:
They went on a two-month cruise, took some samples, and extrapolated heavily. We don’t even know if they’d have found the exact same “dissolution” a hundred, fifty, or twenty-five years ago. Or perhaps the dissolution was particularly bad during that particular two-month period in that particular small location.
This should not surprise us. One reason that so many marine creatures spawn hundreds of thousands of larvae is that many, perhaps most, of them will drift into inhospitable conditions and die for any one of a host of reasons—problems with salinity, turbidity, pH, predators, temperature, the list is long.
With that in mind, look in Figure 1 at the large jump in US landings in 2012, as well as the equally large drop in the following year. One year currents and temperatures and the rest were favorable. But the next year, bad currents took them into the wrong area, or some other oceanic condition was wrong, and most of them died. This shows the beauty of mass spawnings—although the numbers can drop precipitously in one year, the numbers can also bounce back in the following year. It’s one difference between the land and the sea. On land, most creatures except insects have only a few offspring. But in the sea, almost every kind of life reproduces prodigiously. This allows even a few survivors to quickly repopulate the species.
And finally, overall, I see no evidence of the claimed effect of a slightly lower pH on the Dungeness crabs. Remember that as pointed out in my last post, the pH of the ocean along this coast can vary by a huge amount in a single day.
In closing, let me add a couple of points raised in the comments to my last post.
The first regards what scientists call the “diel vertical migration” of the “deep scattering layer”. (“Diel” means “daily”, but they’re scientists so that’s not impressive enough).
In the open ocean every night, billions of tiny zooplankton swim vertically some 500 metres or so up to near the surface and spend the hours of darkness there. Then before dawn, they swim back down to spend the day in the darkness of the depths. I’ve read that it’s the largest animal migration by weight on the planet, happening invisibly every day. There are so many tiny zooplankton that they can be seen on sonar. Here’s an example:
Figure 2. Sonar record of diel (daily) vertical migration of zooplankton in the open ocean. SOURCE
As a long-time fisherman and ocean aficionado, I knew about that amazing migration. But what I hadn’t thought about is that these creatures were going from a pH in the neighborhood of 8.0 at the surface down to waters with a pH around 7.5 down in the deeps … a change of half a pH point in a couple of hours. Kinda dwarfs the predicted slight ocean neutralization expected by 2100 according to the RCP 6.0 of 0.08 pH units … half a pH unit in two hours versus 0.08 pH units in 80 years? No contest.
The other interesting item that was pointed out is that crabs evolved under much higher levels of CO2. I can’t do better than to quote a comment on this:
Decapods evolved in the late Silurian or early Devonian Period, ie under CO2 levels of 4500 to 2200 ppm. If anything, a paltry 400 ppm is not optimum for them.
The crablike form has evolved at least five times among decapods. Crustaceans with shells evolved in the Cambrian, ie under 7000 ppm. The top predator of that period was the crustacean Anomalocaris.
This is very important, not just for crabs, but for all sea creatures. As another commenter pointed out:
During the Devonian period, CO2 was around 4,500 ppm and the oceans were around 30 degC. This era (some 420 to 350 million years ago) was known as the age of the fish. The oceans teamed with life and the largest fish ever to swim the oceans swam during this era.
I’d never thought seriously about the pH of the ocean when CO2 was much higher in the past. One thing’s for sure—past extremely high CO2 levels didn’t cause the ocean biota of the time to start pining for the fjords …
This is one of the reasons I love writing for the web. If I got all scientificized and wrote up something learnedly crabistical for the journals about this, I’d never get the amazing feedback that I get on this site. I learn as much from reading the comments as I do from my own research.
Meanwhile, here up on our hillside above the ocean, the sun is revealing the moss on the redwood tree stumps in verdant splendor …
… and in any case, this should let me put crabs firmly in my rear-view mirror now …
… or not … WARNING: VIEWER DISCRETION ADVISED. The following tale involves allegations of unbridled pediculosis and rampant hallucinations. It is not scientific at all. Proceed at your own risk. And if you are offended by what I’ve written, please don’t fill Anthony’s email box up with complaints. You are proceeding at your risk, not his.
One lovely warm afternoon in Hawaii, I was enjoying the day when I felt a curious itching sensation in my … well … in the location my old drill instructor used to call the “groan area.” I made an examination of said zone, and for the first and only time in my life, I found I was unwittingly providing a home to Pthiris pubis, commonly known as “having a case of the crabs”.
I grabbed one of those jokers as it was in mid-stride making haste towards the nearest … bush … and held it up in the sunshine to take a close look at it. However, there was a complicating factor. No surprise there, things in my life tend to happen in odd combinations.
At the time, I was working as a trainee psychotherapist in a residential therapy setting where we used LSD as an adjunct to psychotherapy. I’ve described my time there, on my blog in a post called Life In The Psychedelicatessen. And as life turns out sometimes, on that lovely Hawaiian afternoon I was well and truly under the influence of that most curious of hallucinogens.
One of the effects of LSD is that you can focus way, way down on something and it appears huge. So when I looked at that tiny crab, it looked something like this …
… only it was coruscating and sparkling and radiating colored light and changing sizes as I watched it … YIKES!
To say I was stunned is a massive understatement.
Despite my impaired state, I walked to the nearest pharmacy, bought some Quell shampoo, and still under the influence, I went home and dealt summarily with the tiny home invaders … and with the ending of that tale, now, perhaps, I can finally put crabs firmly in the rear-view mirror and move on.
PS: My usual request. When you are commenting, to avoid misunderstandings please quote the exact words you are discussing.