A marine biologist studies the creatures that live in the sea. To do this he has to catch fishes and study them when they are dead. Or else he must go down in the water and watch them while they are alive.
One of the most important tools of the biologist is the pickling bottle, containing alcohol or formalin. Without it he would have very little time to look at a creature he has collected, for the animal would soon decay.
Besides the pickling bottle the marine biologist uses a trawl net to catch fishes and other sea creatures. The trawl net is cone-shaped and looks something like a butterfly net. Its mouth is sewn to a hoop, and the rest trails behind. A towline from a ship is attached to the hoop. A heavy weight pulls down the line as the ship sails along.
Water and fishes flow in through the mouth of the net. The water escapes, but the fishes are caught. To catch bigger and fast-swimming fishes, the net is made with large meshes so that the water can flow through easily and the trawl can be towed very fast. To catch smaller fishes, the meshes are made finer.
When the biologist feels that enough has been caught, the net is hauled in. it is tipped out onto a canvas. The various kinds of creatures are counted, and the ones to be kept are popped into their bottles. What is left is thrown back or sent to the ship’s galley.
Sometimes colour pictures are taken of the specimen’s minutes after they die. This is done because many dead fish lose their colour very quickly, even when they are preserved.
Back in the laboratory, the specimens are dissected. This means that they are carefully taken apart in order to examine every part of their bodies. The biologist dissects to learn how creatures are built. Then he can determine their differences and similarities.