Fish Tagging and Essential Fish Habitat (EFH)

In this Lesson Plan:

  • Introduction: For the Teacher

  • Background

  • Student Activity: Essential Fish Habitat

  • Student Activity: Fish Tagging

Introduction: For the Teacher

Key Concept

Data obtained by using methods of fish tagging and telemetry can be very beneficial to determining population size, habitat use and movements of fish. This information can help determine protected Essential Fish Habitats to ensure healthy managed fish populations. This is often difficult because habitat use is dynamic.


Students work individually to learn about how important it is for living organisms to have healthy habitats available to live and grow. Cooperatively, students learn a common method used by scientists to estimate the population using statistics. In the Tracking Summer Flounder in an Estuary Creek Lesson, students go on line with a "web quest lesson" featuring an actual tagging study.

Content Standards

National Science Content Standards: 5-8

Content Standard A:

  • Abilities necessary to do scientific inquiry

  • Understandings about scientific inquiry

Content Standard C:

  • Populations and ecosystems

Content Standard F:

  • Populations, resources and environments

New Jersey Content Standard (grade 8)

Standards 5.1, 5.3


Habitat use is dynamic, it is not a static system.

Habitat Essentials

Life history and habitat requirements are the primary components of Essential Fish Habitat (EFH). Throughout the life of fish, habitat requirements change due to the different needs of the species during a particular life stage. The other component of EFH is the geographic range of the species. This provides information to determine the distribution and subsequent abundance of the species for management and conservation purposes.

Habitat requirements include physical, chemical and biological parameters. The best conditions of these requirements are necessary for the survival of a particular fish species.

Physical parameters

This includes temperature, currents, wind patterns and sediment or bottom type. Reproductive success of fish species relies primarily on the temperature of the water because eggs mortality occurs at low temperatures. Also, in the spring and summer there is a greater abundance of plankton, an important food source for many newly hatched fish species. Sediment type or structure is important for fish species that require specific bottom types. Some fish eggs are demersal, or bottom dwelling, and require sandy substrate, for example, to survive. Adult fish species may inhabit coral reefs or reef-like structures, while other species prefer sandy, gravelly, or rocky bottoms.

Chemical parameters

This includes salinity and dissolved oxygen. Salinity is a measurement of how saline (salty) the water is. Freshwater is water that contains no dissolved salts whereas seawater is completely saline. This is measured in units of ppt (parts per thousand). The ocean is approximately 30 ppt salinity. Estuaries are semi-enclosed bodies of water where freshwater rivers and streams meet saltwater, creating a moderate salinity depending on the particular part of the estuary. In the lower reaches of an estuary, closest to the bay, the water has a higher salinity. Conversely, in the upper reaches of an estuary near the freshwater river, the salinity is considerably lower. Dissolved oxygen (DO) measures the amount of oxygen in the water or how aerated it is. For example, a fast flowing river has higher amounts of dissolved oxygen in the water than a stagnant, warm pool. An environment with adequate DO is vital for the survival of fish.

Biological parameters

This involves predator-prey relationships, competition, migration patterns, and spawning activities. Predator-prey relationships are important because of the trophic linkages (how organisms are related in the food chain). To conserve and enhance a particular fish species, one must determine its food source and conserve it as well as the other components of the food chain. Competition between species for food is also important to understand. Obtaining information regarding migration patterns is critical for habitat conservation. For example, a study beginning in the 1930's in the Middle Atlantic Bight (Massachusetts to North Carolina) has shown that adults and juvenile striped bass (Morone saxatilis) migrate separately, both in time and by differing routes. Young striped bass may spend the winter months in estuaries together and/or apart from older fish. Striped bass are anadromous fish, meaning they feed and live in salt water but return to fresh water to spawn. But, it has been found that some striped bass never even leave their spawning grounds. This has been learned through tagging and tracking individuals, and has yet to be understood.

Coastal and estuarine waters are important habitats for many species of fish and wildlife. These species rely heavily on estuaries and coastal areas for nurseries, feeding grounds, and places to spawn. These habitats have been degraded from the effects of excessive pollution and discharge of wastes and nutrients that wash from the land, are deposited in the air, and are discharged from ships and oilrigs. Human populations and development move in on marine habitats with dredging, filling and construction. As a result of the impacts on these fragile coastal and estuarine systems, Congress developed and later revised the Magnuson-Stevens Fishery Conservation and Management Act to protect fish habitat in order to sustain healthy fisheries. Congress defined essential fish habitat (EFH) as "those waters and substrate necessary to fish for spawning, breeding, feeding or growth to maturity." The National Oceanic and Atmospheric Association or NOAA Fisheries is responsible for carrying out the provisions of the Magnuson-Stevens Act for over 700 managed species of fish ranging from giant tuna to small reef fish. Some species live their whole lives in one place or habitat, while many others move around, utilizing a range of habitats at various times and for various reasons. Scientists are trying to understand what habitat is essential at what stage of the life history of fish species.

There is still so much to be studied but one thing is certain. Essential Fish Habitat IS DYNAMIC!

Student Activity: Essential Fish Habitat

Determining your Essential Habitats

What if an alien suddenly visited your classroom, took a snapshot and returned home with the understanding that humans lived in square rooms with desks and chairs? Would that be a valid assumption, or should the alien follow you around for a couple of days to see all the places you go and why you go there? Do all human habitats look the same? Are they used for all the same reasons?



Small memo note pad and pen

For two days, (Sunday and Monday) keep a notebook in your pocket and record all of the places (habitats) visited and how long the visits lasted. It would be fun if the teacher joined into the activity too. Start with the moment you open your eyes in the morning and end with going to bed, including the sleeping time in the notes. If you wake up during the night and go somewhere, write it down.

Include observations about your habitat in your notes:

  1. What is the approximate temperature? (Look at the thermometer on the wall)

  2. Do you smell anything? What are some sounds?

  3. Why are you visiting this habitat?

On your third day (Tuesday), transfer the list onto an 8 ½ by 11 sheet of paper. (one day on each side).

Go through your list carefully. Write a one page report revealing your essential habitats. Think about some of the questions listed below.

  • Which of the places visited are essential to your survival? Did you visit some places more than once?

  • Were any places so uncomfortable that you wanted to leave? Were any places so satisfying that you wanted to go back someday?

  • What would happen if you no longer had one of these habitats to use? Or what if the habitat was unclean or dangerous?

  • How would you be affected?

  • How would others be affected? (i.e. The waiter in the restaurant you visited if the restaurant was suddenly not there)

  • What if the habitat you really needed existed in another town?

  • Think about some essential places that we only use occasionally but are also very essential. (the hospital, dentist, etc.)

  • Look at time of day. Talk about why some of these habitats are used only certain times of the day.

  • Talk about the "whys". Did you have more than one reason for visiting the same habitat.

  • Why should essential human habitats be conserved?

Fish Tagging Activity


Tagging animals has been an acceptable method for monitoring wildlife for a long time. Using various methods, scientists have been able to observe daily movements, seasonal migrations, and growth rates of individuals in a population.

Fish tagging and telemetry is really the only way to follow the continuous movement of fish rather than their location at a point in time. There are a variety of reasons for wanting to track fish from pure scientific reasons to economic reasons.

Fishes are precious natural resources. The data collected by performing fish tagging procedures could be used to evaluate factors affecting abundance (how many fish in an area), migration patterns (where they go and when), and statistics such as birth rates, mortality rates and harvest levels (how many fish are caught). This information can be vital to good management leading to healthier fish stocks, present and future.

A common resident fish living in the Jacques Cousteau National Estuarine Research Reserve (JCNERR) in southern New Jersey is the mummichog (Fundulus heteroclitis). You may know this fish as the chub, killifish or salt-water minnow. It is also found in salt marshes from Maine to Florida. This is a very adaptable fish, with high tolerance for changes in dissolved oxygen (DO), salinity, and temperature. Since they are so hardy, they are often used in scientific studies. The mummichog is omnivorous, ingests living and dead plants, algae, and especially mosquito larvae.

Larger fish that eat other smaller fish are called piscivorous. Healthy populations of these smaller fish like the mummichog are essential to the survival of the larger fish so it is also important to learn about their populations and habitats. A simple method called mark-release-recapture is often used to approximate the number of resident fish living an estuary. The Petersen Method is the simplest mark recapture method because it is based on a single episode of marking animals.

Activity: Population estimate of Mummichogs (Fundulus heteroclitis)

Suppose your teacher wants you to get population estimates of F. heteroclitis from a small pool in the estuary. Before you begin your actual study, you would like to give the Petersen Method a dry run using Styrofoam peanuts instead of real fish. Your classmates are willing to help you with your experiment. Divide the class up into groups of three.


  1. Since we are simulating this experiment in the classroom, several hundred one inch (approx) pom-poms, cotton balls, peanuts in shell, or Styrofoam peanuts will be representing the live Mummichogs

  2. Brightly colored magic markers for tagging. One for each group.

  3. A 5 or 10-gallon rectangular storage box for each group.

  4. Two cereal bowls or paper cups for each group.

  5. A pen and paper, calculator, or Excel spreadsheet for each group.

  6. Some miscellaneous items to represent organisms that are not in the study


The students in the groups of three decide on who will play what role in the procedure (marker, trapper, and data-recorder). Each team represents multiple trials. Place 100 peanuts (or whichever items you chose to use) in each group's container (but don't reveal this number to your students). Also add in some things that don't belong there like toy marine creatures that may be trapped. These things will be noted on their data sheet if they are caught in the trap. The trapping is done with two small cereal sized bowls or cups, one in each hand. The "trap person" is blindfolded. He/She uses the bowls to trap some peanuts between them. Only keep and count the peanuts that are trapped between the two containers, scrape the others that are hanging on and throw them back in. Measure and record any other creatures that may have been caught in the trap. Count the peanuts and record on the data sheet (M). Mark each of them with one color marker. Then return them to the pool and mix thoroughly (don't let the trapper watch). The trapper does the recapture the same way as the capture. Make sure the blindfold is on, no peeking! It must be random.


  • Count the total number of balls in the trap. (C= total number in the trap.)

  • Separate the marked from the unmarked and count the marked. (R= the number of marked.)

  • (M) = the number of peanuts in the first trapping.

  • From this information we will estimate the size of the population at the time of marking (N).

The Petersen Method equation is:

  1. M = The number of marked fish

  2. C = The total number of fish in re-trap

  3. R = The number of marked fish in re-trap

Use hand calculations, a calculator or a spreadsheet (e.g., MS Excel) to have the students perform the calculations.

Comparing results

You may see some very different numbers for (N) in your data. When doing field-work, there are often several people involved in the data collecting. As individuals, they probably have different attitudes and techniques when doing the sampling, just as our trappers probably had. This can create a "sampling bias" and may be reflected in your data. This is another reason to follow methods closely and collect as much data as possible (more trials).

Let's use the Mean, Median and Mode to compare the results. Continue on your MS Excel spreadsheet or your calculators.

Mean or Average: The mean is the sum of the N's divided by the number of N's

Median: The middle of the distribution of N's. If the number of N's is an even number (you had an even number of groups), then take the average of the middle two numbers and that is your median. For example, 109, 100, 97, and 89, the mean is 100+97/2 = 98.5.

Mode: The mode is the most frequently occurring N. You may not have a mode.

Thought questions

  1. There were 100 peanuts in each container. How close was the average (N) to this actual number? It may be interesting to do this activity again. Do you think that more experienced technicians and additional data might bring the mean (N) closer to the actual number?

  2. Do you feel that this method will give you a good estimate of the actual population of Mummichogs?

  3. In creating your own method for estimating the population in the actual pool, how would you go about tagging the fish?

  4. Are there other factors about the pools and the vegetation around the pool that you would take into consideration? What about predators?


Click Here to Learn about the Weakfish Tracking Study at Rutgers University

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