NZSM Online

Get TurboNote+ desktop sticky notes

Interclue makes your browsing smarter, faster, more informative

SciTech Daily Review

Webcentre Ltd: Web solutions, Smart software, Quality graphics

Discovery

Seashore Summers

Going fishing over the holidays? Have you ever looked closely at the scales of the fish you catch? Did you know that fish scales are made up of two layers, an outer sort of bony layer and an inner thread-like layer which contains calcium compounds. As the fish grows the scales grow in thickness and size by material being added to the bony part of the scale. The material that gets added forms lines of growth. You should be able to see these lines with a magnifying glass.

Use a magnifying glass to look at some scales from different types of fish. Think about what use the scales are to the fish.

Fish scales come in a variety of shapes. Some are diamond-shaped or rhomboid; others are more or less circular while others are circular with a row of small teeth on one edge. Look to see if different species of fish have different shaped scales. Try looking carefully under the scales to see if anything else is living there.

You can wash the scales in fresh water and then dry them and mount them on a card.

Have you ever thought about the fact that humans often use seaweed as food? Next time you visit the supermarket look at some of the processed food that you can buy and see whether it has seaweed or algal products in it. You could also visit a specialist Asian food shop and look at the different types of seaweed available to eat.

Plankton can be interesting to look at with your magnifying glass. An easy way to collect some is make a plankton net. Cut off one leg of a pair of pantyhose. Try to use fine pantyhose without any holes in them. Get an old wire coathanger and untwist it. Make the wire into a circle and twist the ends together. You may need pliers to do this. Cut off any surplus wire. Pull the open end of the pantyhose leg over the wire, fold it and stitch it over the wire frame. Now cut a small (about 1-1.5cm) hole in the other end of the leg, stretch that hole over the jar, and tie it in place with some string.

Next, attach some string leads to opposite sides of the wire frame so that you can pull the net along. These pieces of string need to be quite long so that you can place the jar in the water and quietly pull it along. Look at what ends up in the jar. Use your magnifying glass. Also try washing the pantyhose gently so that anything in them gets washed into the jar.

Greg Walker is a 1996 Science Teacher Fellow.