Donna Cameron, age 9, of Jackson, Miss., former question:

Can a fish drown?

Cats, dogs and human beings drown when they stay under water too long. This is because people and land animals have lungs which can breathe oxygen from the air. When they drown, they perish from lack of oxygen, A fish has gills which can take oxygen only from the water. Nevertheless, he too can perish under water from lack of oxygen. He too can drown. And there are many ways in which this can happen.

A fish's gills are where you would expect his ears to be. They are pink, feathery fringes of tissue. They are protected by curved gill cases which you might very well mistaka for sera . The fish breathes by taking in a mouthful of water and sending it back to flow through the gills and out the gill covers. He seems to be swallowing one mouthful of water after another. Actually he is not drinking all this water, he is breathing it.

The feathery gills are covered with the finest of skin, so fine that the red blood corpuscles come almost to the surface. As the water flows through the fine fringes, the red blood cells grab tiny particles of oxygen and return waste carbon dioxide to the outflowing water. Our lungs do much the same thing with every breath of air. Red blood cells near the surface grab molecules of oxygen and return waste carbon dioxide to be breathed out.

It is not hard to imagine that there is oxygen in the air, for it is a gas and the air is made of gases. But water is liquid, so where is the oxygen? Perhaps it is part of the water for we know that water is a compound of hydrogen and oxygen. But no, this is not where the fish gets his oxygen. Iii most water, there is a certain amount of dissolved oxygen.

It is hidden among the water molecules, just as the dissolved bubbles are hidden in a bottle of soda pop. This free oxygen is what the fish breathes.

Water may have a lot of dissolved oxygen, or a little. When the water is very stale and stagnant, a fish is almost sure to drown, to perish from lack of oxygen. He will drown too in streams that are clogged with silt. Chemicals, when poured into waterways from factories, often add poisons which destroy the delicate gills and cause the fish to drown. Anything which tends to clog the water with silt and sewage will drown the fish.

Aside from impure water, there are practical ways to drown a fish. This may happen by accident when you are trawling. When a fish is pulled through the water very fast, he drowns. This is because his gill covers are pressed down and he cannot breath out. A fish will also drown if he is pulled backward through the water. In order to breathe, the flow of water must be through the mouth and back through the gills. The fish must either hover or move forward. When pulled backward, his supply of oxygen is shut off and he soon drowns.