the ones that got away: science through cross-disciplinary eyes

There's a song by Bruce Cockburn called "The Trouble With Normal" that has stuck with me for years since I first heard it in graduate school. The line in its entirety goes "The trouble with normal is it only gets worse," an observation that applies to so many facets of life: political leaders, repressive regimes, pollution, war, gas prices, age—you name it. It seems to take humans a surprisingly short time to adjust to new conditions, no matter how bad they are. Worse, it seems to take us an equally short time to forget what things used to be like. We dismiss the reminiscing of old folks as just that: dreams of a golden age edited by memory.

This is one reason why studying history is so important. You know: those who forget history are doomed to repeat it, and all that. But history, the kind practiced by historians rather than paleontologists, can also give us a glimpse of what's wrong with our environment, or at least how drastically it's changed in some cases. This is the basis of at least part of the newish discipline of climate study, and some branches of archaeology. Turns out it's also providing a picture of what human predation has done to the size and quantity of ocean fauna.

The History of Marine Animal Populations (HMAP) and its ongoing Census of Marine Life (CoML) project is using records as diverse as old ship logs, literary texts (literary texts! Yay!), tax accounts, newly translated legal documents and even mounted trophies, to track historical sizes, abundance and distribution. Some of the images that are coming to light are, in a word, boggling, but it delights me to no end to see this kind of cross-disciplinary approach. Specialization is a necessity in science, but for big pictures, it always helps to stand back and switch your filters. Dusty stuff like old whaling ships' logs and other documents, for instance, are usually the domain of historians, but they've offered a resource to calculate the pre-whaling whale population with 95% statistical certainty. The decline in population in the very short time that whaling was practiced world-wide is appalling. For example, researchers calculate that southern right whales alone numbered between 22,000 and 32,000 in the early 1800s, declining rapidly once whaling began. By 1925, perhaps as few as 25 reproductive females survived. That's not just predation. It's slaughter on the scale of the buffalo.

We're not used to thinking about whale populations in terms of tens of thousands. As Jennifer pointed out when I first posted the link to this particular study on Facebook, that phenomenon is something that biologist-turned filmmaker Randy Olson calls "shifting baselines," and those shifting baselines can be deeply deceiving. Andy Rosenberg, of the University of New Hampshire, points out that appraising modern marine life through the narrow window of observations during recent decades "skews perceptions" of "natural" marine life sizes, abundance, habitats and vulnerability. Put another way, we're pleased when whale populations climb back to a few thousand or so, but the real baseline to measure their progress against is much larger. When you know that, you realize the poor whales still have a long way to go and their population gains seem far more fragile and worthy of further protections. Having the correct baseline, this one provided by historical documents not current scientific census data, can help form the correct international policy to protect them.

Then there's that size issue.

Fishermen, God love 'em, always talk about the one that got away, and it's inevitably a huge beauty that no one believes actually existed. Fish just don't get that big, unless you're fishing for the big guys like marlin or grouper, right? The photo at right (courtesy of HMAP/CoML) illustrates the decline in size, species diversity and abundance of gamefish in the Florida Keys between 1956 and 2007. There are some real beauties any fisherman would brag about in the top, earliest photo that make the recent catches in the bottom photo look puny-ass by comparison. The study found that from 1956 to 1960, large groupers and other large predatory fish dominated the catches, including sharks that averaged nearly two meters long. By contrast, small snappers with an average length of 34.4 cm dominated catches in 2007. Just today, in one of my cooking magazines touting the wonders of summer trout, was a photo of a guy holding a wee little fishie that barely spanned both palms, something I would have been told to throw back as a kid. Overfishing makes the catch amounts and individual sizes smaller simply because fish aren't allowed to fully mature before they're caught and eaten. You don't grow a 500 lb. grouper overnight. It takes, in fact, about 30 years. An 800 lb. grouper may be as much as 50 years old. I'm glad my middle age spread isn't that drastic. Freshwater fish grow more rapidly, but they still take time to mature into the three-foot-long pike my uncle pulled from the lake 40 years ago.

This drop in average fish weight isn't a modern phenomenon. Once humans started fishing with nets or weirs, the fish were in trouble. The Romans apparently were fishing with nets quite early on, but it wasn't until the middle ages that evidence of reduced sizes in the fish themselves begin to be recorded. That's when improvements in boat design and equipment allowed fishermen to start dragging those nets farther from shore, rather than just casting them and hauling them up, as in the picture above, from an 11th century Byzantine manuscript (International Journal of Nautical Archaeology/CoML). But in the course of this study, researchers determined that the human impact on the oceans began much earlier than previously thought, as early as the Middle Stone Age: 300,000 to 30,000 years ago, which is 10 times earlier than previously believed.

This is where I get really tickled about this kind of study. Where does the evidence come from? Not just archaeology. That can only find physical evidence of the fishing methods and tools, and if you're lucky, fish bones in the midden heaps. Nope, the evidence about how small the fish have gotten comes from literary texts. Latin and Greek verse written in the 2nd century CE was used to determine that the Romans were even then learning to trawl in a limited way and finding that, over time, it reduced the size of the fish they caught. Old logbooks and collections of sea lore were also studied for comparison purposes. Even old restaurant menus were scrutinized. Researchers also cited a text written in Sicily in 1153 that describes the seas of the North Atlantic as having "animals of such great size that the inhabitants of the islands use their bones and vertebrae in place of wood to build houses. They make hammers, arrows, spears, knives, seats, steps, and in general every sort of thing elsewhere made of wood."

Our biggest problem with this kind of literary evidence is that we find it hard to believe, in view of our own experiences. It's like the hillbilly who, when a giraffe was shown to him, declared, "There ain't no sich animal!" Krakens? Yeah, right. But we know that deep sea (and polar ocean) critters often exhibit an inordinate gigantism we didn't expect and can't fully explain, like the giant isopods found on the deep sea floor (imagine a foot-long pill bug). And there really are giant squids, though one big enough to pull down a ship hasn't yet been found. And to be fair, there's a great deal of exaggeration and sheer make-believe in the early histories. Look at Isidore of Seville's Etymologies, which describes the Blemmyes, who were an actual African tribe, as having their faces on their chests because they had no heads. To be fair, he stole it from Pliny the Elder, whose Naturalis Historia was the first encyclopedia and model for those that followed, at least in format if not veracity.

So how do you tell the fact from fiction in old sources? Statistical analysis and confirmation from other sources. In addition to the literary sources, researchers used photographs of previous catches, legal documents, tax accounts, whalebone buttons, paintings, old pavements, isotopes, and ice cores to develop backcasts. This cross-disciplinary approach gives a much broader picture than just observations of what's currently in existence. It's studies like this that help us inot just magine but undertstand, for instance, what Manhattan might have looked like when Henry Hudson sailed into the harbor or what the world might look like without us.

Apparently, a lot bigger, with a lot more in it. At any rate, it's good to remember that our "normal" isn't necessarily the norm.

Comments

[Captain Skellett]

I love that line in Othello - "men whose heads do grow beneath their shoulders", and also I love that you referenced the Beast - man, that was my favourite movie for ages (after the Labyrinth), and I can't find it anywhere anymore (especially not in Australia). I remember it being really good but, as you pointed out, memory being what it is it was probably not that great.

[arby]

"...Middle Stone Age: 300,000 to 30,000 years ago..."?

[arby]

Ah, okay.

[Danna Staaf]

Great post! Fisheries science is so fascinating yet so depressing. "Overfishing makes the catch amounts and individual sizes smaller simply because fish aren't allowed to fully mature before they're caught and eaten." Of course, if this were the whole story, extinctions would be even more rampant than they are. The species as a whole survives fishing pressure because of genetic variability in size at maturity--those few fish who mature at smaller sizes get to reproduce before they're caught, passing on genes for early maturity, which come to dominate the population as a whole. Artificial selection at its finest, but also its most unintentional!

Incidentally, last year I saw a very cool seminar by one of the major researchers on this project, Heike Lotze. I just noticed she has a link to the Science paper on her website, for the very interested:
http://myweb.dal.ca/hlotze/