Some fishes are famous because of their reputation as fierce,
fear-inspiring predators. Others are known for their bizarre looks.
Yet still others' claim to fame lies in their large size or their
popularity among sportfishermen. And among the diving community there
are certain fishes that are especially sought because of their
sure-fire, crowd-pleasing photographic appeal.
Certainly then, any fishes that would have all of these qualities should be real hits. And hammerhead sharks exemplify all of these&emdash;and more.
As a rule of thumb, hammerheads are denizens of the tropics. Divers are often mesmerized by tales&emdash;and pictures&emdash;of the large build-ups of hammerhead sharks off the Galapagos and Costa Rica. Scores of these fearsome (albeit also rather silly-looking) gigantic fishes knock around such places, making for such real bang-up opportunities for adventurous divers and underwater photographers.
But these are not the only spots to spot hammerheads. Worldwide, there are nine species, in all tropical, subtropical and temperate seas. They all have some sort of what is properly termed "flatted lateral extensions of the head," or in practical terms, what looks like they put their face under a steamroller!
The reason for this odd-shaped head is not really clear. It may help them to detect their prey (which are typically fishes, including rays and skates, but also with some other species, and other hammerheads). Or it may increase their maneuverability. In any case, it certainly gives them all a very distinctive and easily identifiable look.
Getting a handle on which hammerhead is which is largely based on the shape of these flattened faces&emdash;how many lobes, how long they are in relation to the body, and the like. Of course, overall size, relative size of their gill slits, and range can also help nail down the correct identity.
California doesn't have the large numbers of hammerheads stalled around like the more southern areas. In fact, even a single hammerhead shark sighting is an uncommon occurrence. But when warm waters push their way north, hammerhead sharks often come along. The three species to look for are the bonnethead (Sphyrna tiburo), the runt of the group at only 4 1/2 feet in length; the smooth hammerhead (Sphyrna zygaena), which can reach 11 feet; and the much rarer scalloped hammerhead (Sphyrna lewini) which averages 5 to 9 feet in length, but has been known to achieve a whopping 14 feet!
For the most part, all hammerheads are open ocean dwellers, although they do occasionally meander into shallower water. This is when they can be best seen by divers and recreational swimmers&emdash;usually scaring the daylights out of the latter group.
For hammerheads are among the feared sharks that can attack people. This reputation is not entirely unwarranted. For the most part, however, they are not exceptionally aggressive. But if a diver teases and pokes one, or a spearfisherman tempts one with a freshly caught fish&emdash;well, a hammerhead may just comply and deliver a nasty bite. The same is true of anglers who seek hammerhead sharks for sport. If someone brings one on board a boat and puts his hand too close to the shark's mouth, what do you expect?
Hammerheads do not lay eggs, but their young develop within the females. The number of pups in a litter and their size at birth varies according to species. The scalloped hammerhead, for example, has litters of 15 to 31 pups that are 6 to 12 inches long.
Like so many types of sharks throughout the world, their fear-inspiring reputation and the pressure of human activities, such as sportfishing and finning has chiseled away at their overall numbers. The Shark Specialist Group of the International Union for the Conservation of Nature considers all Sphyrna species of hammerhead sharks as ones to watch as being potentially threatened with extinction. The precise status is hard to really establish, because it is challenging to get a handle on the actual numbers of wide-ranging, open ocean species, such as the hammerheads.
For now, though, it seems that hammerheads are fishes that just about have it all. With their bizarre looks, they are easy to recognize, are fear-inspiring and fearsome, are large and popular among sportfishermen to catch, and divers to observe and photograph. And now they are receiving special attention in conservation circles. These truly are fishes that people should not want to knock!