Where do the fish go?

This was an assignment I had to write for my Environmental Communications course. I figured it would be good to share some of my work with you. Feedback would be greatly appreciated. I have no title for this piece.

Coral reefs are living environments and home to many fishes. According to a study published in the Journal of Experimental Marine Biology and Ecology, 67% of fishes moved to healthier coral when their coral home dies. This new coral home is usually close to their original home.

The study tested how long it takes the fishes to move to a healthier spot once the coral dies and how many of them will move.

Three scientists from Australia found that there are three factors that determine whether the fish move. They are the health of the original coral home, whether a new home is available and if that new home has other fishes they can breed with. Competition from other fishes is a big factor that causes the fish not to move.

Corals are very tiny, colourful marine animals. They live close together in colonies and have a hard skeleton made from the same material as seashells.

Fish love happy coral. Hurricanes, changes in the sea temperature and other things like pollution make the coral unhappy. Coral bleaching happens when the unhappy coral move away and leave behind the white skeleton. Coral bleaching does not happen all at once on the whole reef. It happens in patches. The coral never moves back if the conditions remain the same or get worse. When this happens the reef is said to be dead.

Disturbances to coral reefs can happen naturally. Human activities can also cause disturbances to coral reefs.

Human caused disturbances are adding to the effects of natural disturbances. This is threatening the lives of many animals and plants as well as how the environment is working.

The study found that coral bleaching did not affect the fish. They remained at the bleached reef.

Although the fish chose to stay at the bleached reefs, their dark or colourful bodies against the white reef make them easily seen.

A dead reef keeps its structure, but it still does not have everything fish need to live there. When the coral dies another tiny plant called algae moves unto the skeleton and starts growing. This new plant does not support the fish and makes it harder for the fish to find hiding spots from other fish that want to eat it. Once the reef died the fish moved to another reef.

Certain fish rely on certain types of coral colonies. If the fish is to move successfully and live, it needs its preferred coral colony to move along.

While some new fish came from the dead reef to a healthier one, some from the healthy reef left. The total number of fish did not change which means that no fish died because of the death of the reef.

Each school of fish has a hierarchal system. The new fish cause the fish at the bottom of the system to move out.

The presence of other fishes at healthy coral reefs stopped some fishes from moving to a new reef. It’s like a high school cafeteria. The new kid wants somewhere to sit and each his lunch. He tries to find a table which has other people so he doesn’t sit alone. Each table he approaches gives him the look of death so he goes back. It’s the same thing with the fishes.

Fish from the dead reef approach the new reef in the hopes of finding a new home. Fish from the healthy reef chase them away.

The fish from the healthy reef may feel threatened by the new fish, and because of this they chase them away. The new fish may be more aggressive or social dominating. If they are, food, space and mating partners may be affected.

When choosing a new reef fishes look for “good neighbours.” A good neighbour is one which the fish can breed with.

Fish preferred having other fish they could mate with over a healthy reef. Of the 64% of fish that were successful in finding a new reef, all except for 2 chose a reef with good neighbours. Some of the fish travelled far to find a new reef with good neighbours.

Fish choose reefs with good neighbour not only because they can mate with them but for additional protection against predators.

The scientists concluded that an important factor in regards to the movement of fish was the presence of other fish it could mate with. Conversely, competition for food, shelter and mating partners did not hinder the movement of fish. Fish also moved out from dead coral before the structure of it was gone.