Pollution | Protect the Ocean

The Leading Cause of Fish Decline

September 20th, 2011

Just a few hundred years ago, the world’s rivers and lakes teemed with gigantic fish. Freshwater fish were so plentiful that they were used to feed farm animals and fishermen found it hard not to make a catch, according to a new review of historical accounts.

Oceans get most of the attention when it comes to aquatic conservation. But the new study suggests that freshwater species have declined precipitously, too, and that conservation efforts aren’t aiming big enough when it comes to rivers, lakes and streams. Bodies of freshwater, they found, have changed dramatically over the years.

A group of scientists used simple mathematics last month to argue for sensible use of the oceans: A live swordfish is at least a thousand times the value of a dead one at the fish market. When a shark fin is worth 50 times more than the rest of the carcass, fish workers often slice off the fins and toss the shark back into the water to die a slow death. Sharks are also killed for meat, leather, and teeth and for their cartilage, which is used as a treatment for anything from cancer to the common cold.

Fish species are being taken from the seas faster than they can regenerate.
In addition to overfishing, pollution from the discharge of oil and chemical contaminants has taken a huge toll on global marine fish populations. Coastal regions are particularly affected by pollution. Some 90 percent of the world’s fish catch comes from the third of the oceans near the coasts.

A quarter to a third of the world’s catch is also discarded by fish workers as “by kill,” endangering some species. Non-traditional fishing methods, including the use of satellites, sonar, high-intensity lights and cyanide, which is used to temporarily stun fish, are also endangering species. Nylon fishing nets, weighed down by chains and dragged along the seabed also kill sea urchins, crustaceans, and starfish.

People rarely appreciate the major impact that even a fairly moderate amount of fishing has on certain freshwater stocks. We look at fish as a commodity and the oceans as supermarkets. It’s as if peace has been declared on land and war in the oceans. Remember, it’s okay to use what’s in the oceans but not to use it up.

Reference: Illustrated Encyclopedia of endangered animals.