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Are the fish biting? Your challenge is to investigate how three commonly used fishing techniques impact a population of fish. And you’ll use a method called catch, tag, and release, along with a simple mathematical formula to estimate the size of a given population of fish. Have I hooked you enough to start this investigation?

Planning and Carrying Out Investigations

Fisheries Brochure

Fisheries Brochure

What is a fishery?

A fishery is a place where fish are caught. The term can include the industries involved in the catching and processing of fish.

How are fisheries maintained?

The regional governments create laws to protect the fish from overfishing. Usually these laws consist of bag limits, limitations on fishing methods, and limitations on the times of year that fishing is permissible.

What is the catch, tag, and release method?

This method is a way for scientists to measure a large population without counting every single member. Scientists catch some members of the population, count them, tag them, and let them return to the wild. The scientists come back later and catch more members of the population. They count the number that are caught as well as the number that are tagged. They can then estimate the population by multiplying the number of members caught the first and second times and then dividing by the number that were tagged.

What is the red drum?

Red drum fish are found in the Gulf of Mexico and in the Atlantic Ocean from Florida to Massachusetts. These fish lives near shorelines and around structures and outcroppings. This means it is easy to get to where it lives. The red drum were declared a protected game fish by President Bush, so that they cannot be commercially fished in Federal waters. Recreational fishing of red drum is popular. Red drum are reddish-brown with a white belly. They also have a black spot on their tail. They are called "red drum" because of their color, and they make a drum-like noise to attract a mate. They have down-turned mouths and usually feed along the bottom of the ocean. However, if there is enough shelter, they will eat throughout the entire water column. Red drum usually eat small crabs, worms, and smaller fish. For a red drum population to grow, it needs sufficient food, clean water, and shelter.

How does fishing impact population growth?

If there is enough food and shelter, the growth of a population is proportional to the size of the population. More adult fish means more baby fish, and fewer adult fish means fewer baby fish. The growth in the population is the number of baby fish minus the number of deaths. If the population growth slows enough, the rate of fish deaths from fishing will outpace the number of new fish that hatch and survive. When this happens, the population will start to shrink. Because smaller populations result in fewer baby fish, if the fishing continues, the shrinking will accelerate until the fish population is gone. Furthermore, since smaller populations grow more slowly than larger ones, it will take a long time for the fish population to recover even if fishing in the area stops. Even though red drum cannot be commercially fished, recreational fishing threatens its population. Recreational fishing does not use the large trawling nets used by commercial fishers, but it heavily impacts the red drum population because the fish lives so close to the shore and because it is fairly popular.


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