Fisheries science can be interesting as well as educational. The class project described below combines hands-on biology, data collection, data interpretation and computer skills in a modular package well suited to a class of high school students or to individuals preparing an exhibit for a Science Fair. Though intended to expose the student to a range of scientific activities, this is not just a "make work" project: this type of activity represents a genuine portion of the job of a fisheries biologist.

The project is focused on the analysis of a group of fish, and the calculation of their rate of growth. Materials required include the following:

- a sample of about 30 whole or gutted fish of various sizes; where the costs of purchasing these fish are too great, the heads alone can be used. Given appropriate lead time, fish processors and seafood markets will often save heads for teachers at no cost

- measuring boards or rulers; at least one balance for weights

- surgical type gloves (optional)

- fish knives and forceps for otolith removal

- dissecting microscope(s) for age determination, as well as clay and vegetable oil

- computer program capable of simple graphs or charts; alternatively, graph paper can be used

Biological Sampling (1 hour): Working in pairs, the group weighs and measures each fish or head (a minimum of 2 fish per pair). Lengths should be recorded from the tip of the nose to the fork in the tail (or the tip of the tail if there is no fork). If heads are being used, the length is the tip of the nose to the back of the gill flap. Each head is then cut open and the otoliths removed, as described in How to remove an otolith. Otoliths can be stored dry until the next class, or if there is sufficient time, can be aged immediately.

Age Determination (1 hour): Work in pairs. Prepare and age each pair of otoliths (described in How to determine the age of a fish). Once completed, each person should circulate to the other stations to examine the other prepared otoliths. This is intended to familiarize the students with a broader range of otoliths and preparations. Upon return to their own otoliths, the pair should then reexamine their own otoliths, and if warranted, revise their ages. Once satisfied, an average age for each pair of otoliths (each fish) should be calculated, since the 2 otoliths may or may not result in the same ages. The average age for each fish should then be put up on the board, along with the corresponding length and weight. This will result in 3 columns of numbers - one each for age, length and weight. The data for a given fish must be all in the same row. All students should copy down the lengths, weights, and ages for all of the fish put down on the board (eg- there should be about 30 rows of numbers on the board). These numbers make up the data for the following class.

Data Analysis (1 hour): The data for any one fish may or may not be representative of other fish. It may not even be correct. But when a sufficient number of fish are examined, the overall trend is much more likely to be correct.

Working individually, the students should enter the data into a computerized spreadsheet or charting program. The data should be entered as they were recorded on the board; that is, one column for length, a second for weight, and a third for age, with one row per fish. Using either the spreadsheet program (or graph paper if computers are not available), the following graphs should be prepared: