Why sharks matter: a reply to “sharks are sub-par at best”

Recently, Andrew attempted to correct several commonly-held misconceptions about sharks. He raises some good points, but I disagree with his conclusions. I believe that sharks are incredible animals, but I think it is far more relevant that sharks are important animals.

Most of Andrew’s concerns involve how the media and the general public think of sharks, and it is hard to disagree with the claim that these groups tend to lack an understanding of certain aspects of science. In general, though, I don’t think it’s a good plan to judge the validity of a movement by the depth of understanding of the rank-and-file members. Sharks are significant and interesting for reasons that have little to do with how well some people understand science.

Here some specific points I have issues with from Andrew’s post:

“While technically true that sub-class Elasmobranchii has been around for hundreds of millions of years, modern sharks are, well, modern. They’ve been evolving for exactly as much time as just about everything else currently alive.”

This is completely true, and reflects a fundamental (and alarmingly common) misunderstanding of how evolution works. The reason why shark conservationists bring up that sharks have been around for 400 million years has nothing to do with the mistaken belief that sharks are unchanged evolutionarily, however.

While many shark species have gone extinct throughout time, species of sharks have survived every great mass extinction event that the planet has ever faced. This puts into perspective the magnitude of the destruction wrought by some modern commercial fishing practices.

The fact that there were animals recognizable as sharks long before there were dinosaurs also has ethical significance. Environmentalists have used the argument “they were here first, they have a right to exist” for decades with reference to other animal species. Sharks were here before many of these species were.

This species has indeed been evolving as long as every other modern species

“Yeah, some sharks stayed sharks, but the common ancestor of nearly all vertebrates was some kind of elasmobranch.”

This is also true, but Andrew seems to be saying that the fact that the common ancestor of all vertebrates was an elasmobranch means that elasmobranchs are lame. I think it means they are, for lack of better words, pretty special.

The common ancestor of all vertebrates may have been an elasmobranch like this guy

“sharks are a fairly sub-optimal design. They’re bad at regulating heat, removing waste, they’re very energy inefficient. But much much worse than that, modern sharks are bad at evolution. They are slow reproducers with small brood sizes. There is low genetic variability between generations. All that builds up to the fact that sharks can’t quickly adapt to changes in their environment”

Some sharks, like makos and great whites, are actually very good at regulating heat. The larger point stands, though. Nothing is perfectly adapted to its environment, and the belief that sharks are “perfectly adapted” also reflects common misunderstandings of how evolution works.

It is  true that sharks have few young and reproduce relatively late in life, and this has enormous conservation significance. However, I don’t think its fair to claim that sharks are lame because they aren’t well adapted to conditions that have only been around for a few decades (modern commercial fishing practices). Their strategy has worked pretty well for the last few hundred million years- they’ve survived mass extinction events that led to the extinction of many whole classes (and even a few phyla) of animals. Very few animals are capable of adapting with the speed required to survive human expansion, so by Andrew’s definition of lame, most animals are lame.

While unable to quickly adapt to environmental changes, the bonnethead is still an impressive animal

“if you drop a bucket of chum overboard, they’re not going to immediately know several miles away, you’ll have to wait until the chemical cues reach them. That’s not very impressive. Most animals have a range of chemical cues they can pick up on in incredibly low dilutions”

I would say it’s more true that “many” animals have a range of chemical cues that they can pick up on in low dilutions rather than “most” animals, but sure, having strong senses is far from unique to sharks. I still say that sharks’ senses are impressive- they can see better than we can in clear and in murky water, they can tell the difference between a wounded and a healthy fish by the pheromones that fish gives off and by the vibrations made by that fish moving, and they can even detect bioelectric fields. I’m impressed. Most of the people who hear about it are impressed. The fact that some other animals can do some of these things doesn’t make it less impressive. Just because other people have won a Nobel prize before doesn’t make it less impressive when people get a new one each year.

The cephalofoil (modified head shape) augments the senses of hammerheads and bonnetheads

“There’s a whole mess of different ways to be a predator, and sharks are fairly dull. They don’t have venom, adaptive camouflage, they don’t regularly fight giant squid or snipe insects out of the air. They don’t have sonar, radar, infrared.”

Billionaire  entrepreneur Steve Wynn’s primary philosophy is “doing the basics better” rather than trying to come up with brand new business ideas. Sharks don’t need any fancy newfangled adaptations, they get the job done pretty well with sharp teeth and speed. Many species of sharks are the apex predators of their ecosystem.

A 9 foot tiger shark- "the basics" done pretty darn well.

In summary, Andrew seems to be claiming that since many commonly-held beliefs about sharks are wrong, sharks are lame. I disagree.

It is more relevant, however, that sharks are important than that they are cool. The fact that some people don’t understand evolution or chemosensory systems doesn’t change the fact that the loss of sharks results in serious ecological and economic problems.While sharks are in fact fascinating and not lame, this isn’t why we should care about them and protect them. We should care about sharks because they matter ecologically and economically.


March 13, 2010 • 1:57 pm