Tag Archives: Sharks

Who cares about sharks?

This is shark week. So, I have some thoughts about sharks.

If they were lions, I’d have some good stories about the times I was nearly eaten by this or that lion. But my engagement with super predators has been mainly terrestrial. As a kid, fishing in swimming in the ocean, I’ve had a few encounters with sharks, like when fishing for mid size predators, like striped bass, among shimmering schools of mackerels. Now and then all the mackerel would give up on their shifting, roiling, herd strategy which allowed them to feed on smaller fish while at the same time avoid the bass, and switch to plan B, vamoose. One moment there are mackerel everywhere with the occasional bass flashing by. Next minute, there is nothing. And for that moment the only food in the sea is whatever is on your hook (probably a fragment of a mackerel). A certain proportion of the time, the shark that chased away the mackerel takes your bait.

I remember the first time that happened to me. I was probably around eight years old. There are usually a few old salts around any fishing pier, and there were that time. They came running over. “Eyup, you’ve hooked a dogfish, laddie. Reel it in as fast ‘you can, with luck the line will break.” But then the line doesn’t break and you pull a shark up out of the sea. “Careful, laddie, a dogfish has a spine on it, it can give you a bad gash.”

Squalus acanthias lacks anal fins and instead has spines. (Coincidence? I think not.) When cornered or beached, they arch their back and flop backwards, and in so doing, can slash up attackers. These fish have been around for several million years, being small (big ones barely get to a meter long), spiny ans slashy. In those days, if you caught one, it would be shared among the other fisherfolk as bait. Maybe chopped up for chum. I don’t think anybody ate them. These days, with the idiom “there are plenty of fish in the sea” turning rapidly in to an archaic phrase our the next generation will wonder about, spiny dogfish are probably a delicacy on some menus.

Squalus acanthias has another interesting property besides the menacing spines: they are canaries. This is one of most common species of shark in the world, but are threatened or vulnerable globally, and critically endangered in the Northeast Atlantic. Their population levels are down to less than 5% of natural in some areas. This is because the main food for Squalus acanthias in some areas are highly desired commercial fish such as salmon. We humans are directly competing with Squalus acanthias for food, and at the same time, hunting them.

We should all avoid using shark products. You can usually find out if shark material is used in the products you buy (it is not all food) by paying close attention to the labels. Obviously, you should not eat shark meat.

There are a gazillion organizations that support sharks. I have no idea which ones are good, which ones are shady. Also, at this moment of political crisis in the United States, I suspect that donations for shark supporting organizations are going to take it in the gills, as most of us donate to candidates or other causes.

If you have opinions or information about shark conservation groups that are worthy, please post that info in the comments.

Great White Sharks in Captivity

There aren’t any. But, aquaria have many times tried to make it so, and it always goes bad for the shark. The basic problem is that great white sharks are pelagic, and it is very hard to keep pelagic creatures in a confined space, and the largest aquaria are very confined from the point of view of a large pelagic animal.

greatwhitefeedingonsealAnother problem would eventually become important in the event that an aquarium managed to keep a great white shark alive long enough. When they are young, great white sharks dine on fish. When they are adults, they seem to prefer mammals. So, imagine feeding time at the zoo with an adult great white shark ….

Anyway, VOX has put together a really excellent video on the history of great white sharks in aquaria. Wildlife biology or marine biology high school teachers take note, this video has a lot of learning in it about stuff you probably teach!

For example, you learn what “pelagic” means.

Here’s the video:

I’ve seen great white sharks in the wild several times. You can to. You just need to know where to look. I suggest the southern coast of South Africa. Oh, and if you are going to go around spotting sharks, you’ll need a good shark spotting guide.

Guide to the Sharks of the World

I love field guides. One should own a lot of field guides, not just to things you might go out in the field to see and identified, but just to browse through.

David Ebert, Sarah Fowler and Marc Dando have produced A Pocket Guide to Sharks of the World It is put out by Princeton, which does excellent guides (this is part of their Pocket Guide series).

From the Princeton site, about the authors:

David A. Ebert is the program director for the Pacific Shark Research Center and a research faculty member at Moss Landing Marine Laboratories. Sarah Fowler cofounded the UK Shark Trust and the European Elasmobranch Association. She has been a member of the IUCN Shark Specialist Group since 1992 and is currently vice-chair of international treaties. Marc Dando is a freelance artist specializing in marine ecology and wildlife.

Don’t go to sea without this book, just in case you come across a shark.

This is a standard Petrides/Peterson style guide, with plates showing various sharks, and associated ID text. The front matter includes guides to fins and teeth, some basic information on biology and reproduction, the usual overview of external anatomy so you know what the terms are (so you know what a caudal keel is, and such). There is an extensive guide to teeth. There is a species checklist, an excellent glossary, and a list of species. Here’s a PDF of the book’s Introduction.

There are 501 species of shark known today, and all of them are in the book.

Screen Shot 2015-07-01 at 6.29.10 PMOne of the coolest things about the book is how they show relative size. Sharks vary a great deal in size across the diverse species. To show the size of the sharks on a given page, the authors use an image of a human next to the shark.

There really aren’t any other field guides out there like this, as far as I know. In my experience, if you come across a shark in most waters, it is highly likely to be one of a small number of common species and you don’t really need a guide to determine what it is. You just need the old salt down on the pier to tell you. But beyond the first couple of common species, the next shark or two down the line in commonness may be any of a large number of sharks, and for that you need a guide.

Sadly, but out of necessity, the guide includes information on identifying sharks from the fragments that are cut off and sold by shark hunters and poachers.

Sharks are cool, and this is a cool book.