It was 1974 when the late Peter Benchley’s novel Jaws was published. It became an immediate best seller; its success spun off a hit film that was followed by three sequels. The first Jaws movie was a bona fide blockbuster (at the time the highest-grossing film to date), and four decades later it remains a durable classic.
The sensationalism of a primitive sea creature, capable of evil thoughts and acting on them, attracted a considerable following. Soon an aggregation of Jaws-related merchandise was in the stores, and the Universal Studios theme parks in Florida and Japan built elaborate attractions based on the book and movies.
In the real world of sharks versus man, the actual situation is far from sinister. What sustains part of the mythology is that shark attacks on humans make great news stories. Actually, only four species of sharks are guilty: great white, white tip, tiger, and bull.
Globally, Australia, South Africa, and the United States have the greatest number of attacks per year. The United States is highest with an average of 16 annually and a fatality every two years. Of the millions of Americans who go to the beach each year, about 3,400 swimmers will drown while a shark will kill only 1. Clearly, the most dangerous part of the family outing is the drive to and from the beach!
Fossil records show that sharks are some of the oldest living creatures on our planet. First evolving more than 400 million years ago, before terrestrial vertebrates existed, they are at least 200 million years older than the dinosaurs. Today there are nearly 500 species, widely diverse in form and function.
With such diversity it is difficult to describe the average shark, but there are some useful generalities. They are cartilaginous fishes; that is, they do not have bony skeletons like other fish species. Therefore, their skeletal structures are much lighter, and that combined with their supple skins means they are fast and maneuverable. Most can swim prolonged distances at a speed of 5 knots and some have “burst” speeds of more that 10 knots. Several species are able to feed at depths greater than 7,000 feet.
They come in many sizes, from about 7 inches to over 40 feet in length for the whale shark, the largest fish in the ocean. Essentially toothless, the whale shark is a filter-feeder. In order to get the food it needs, it ingests huge quantities of plankton.
The biggest toothed shark is the great white, which can grow up to 26 feet long and weigh in at three tons. They are capable of burst speeds up to 30 knots. With a life span averaging 70 years, the great whites’ only predators are the orca (“killer”) whale and man.
As a top predator, sharks play a major role in the balance of the World Ocean ecosystem. Remove them from the prey-predator chain and the rest of the ecosystem suffers. And that is what is happening today.
Some species of larger sharks are now listed as “threatened” or “endangered.” In the past three decades their numbers have declined by up to 90 percent. This means eventual extinction, and the trend will accelerate.
Causes for species loss are diverse, but the major one by far is the commercial and recreational harvesting of more than 100 million sharks per year. Much of this is to meet an increasing demand for shark fins. It is estimated that between 26 and 73 million sharks supply Asian (mostly Chinese) markets with fins for shark fin soup. The practice of “finning” cuts the fins from living sharks, then returning them to the sea where they die. It is the huge unreported impact of illegal fishing activities that cause such wide variances in the numbers of sharks taken.
The financial rewards for the trade are so high that moves to regulate this market have been futile. A major part of the solution must be to reduce or eliminate culture-driven demand for shark products.
A major problem in estimating the interactions of sharks with mankind is the difficulty of getting good data from all the oceans. From the developed nations, the data is generally excellent. From developing nations, the data is poor if it exists.
Without good numbers it is extremely difficult to develop conservation schemes to protect the most vulnerable of these top predators. Fortunately, there are many active international organizations concerned with shark populations. They have sounded the alarm that these key elements in the ocean-life system are at risk. If the oceans lose these top predators, we will all lose.
Dr. Walsh, a marine consultant, is a retired naval officer and oceanographer. During his naval career he served at sea in submarines and ashore in ocean-related research-and-development assignments. In 2010 he received the Peter Benchley Award for Ocean Exploration.