Investigating the Beach

As with the other Sea Keeping exercises, investigating the beach offers a range of opportunities. Start with the easy ones and select activities that are appropriate to the participants and the schedule. Some projects might be done as a special project, others could be a class project. Most lend themselves to adjusting the effort from easy to challenging.

• Map the beach. Starting with a copy of a Council map of the beach, add landmarks. Indicate key points with measurements (using measured lengths of rope, bearings, triangulation, tape measures). Where do pipes, rivers, or other sources of water enter the beach? Are there stormwater drains that empty onto the beach? When were they installed? What do they drain? Are there underground springs? Give your map to someone else to test it. Can they find the same landmarks and places? Indicate North on the map and enter the latitude and longitude co-ordinates, and the name(s) of the beach. Indicate the horizontal profile of the beach and type of sand in different zones. Is the beach sheltered or exposed to large waves? Record this information.
  
• One of the measurements you will try to determine is the total number of shellfish per unit area of the beach. This means working out the number of square meters of the area measured. First, you will need to work out the scale of your map. The first step is to go to the beach and actually measure the distance between two obvious landmarks that are located on the map or on the aerial photograph. Next, photocopy the map (or tracing of an aerial photograph) using graph paper with 1-mm squares in the paper tray. Measure the distance between your two landmarks on the map (say 50-mm) and divide this into the real world measurement (say 200 metres or 200,000-mm). This yields the scale of the map, (4,000 to 1 or one millimetre equals 4 metres). Count up the 1-mm squares within the area measured to get the total area of the sampled area in square millimetres and convert this to square metres using the map scale. For example, if the area measured contained 4000 square millimetres and if each square millimetre represented 4 meters by 4 meters as in our example, the total zone measured would be 64,000 square metres.
  
• Look for old photographs of the beach taken by people in the community or in a local library or museum. Can you find (from landmarks in the photos) where the photos were taken from? Can you take a photo from the same place again to show the changes? Are there old survey maps of the beach? How do the very old maps compare with the beach today? Obtain aerial photographs of the beach - perhaps covering a long time span to see changes in the beach and surrounding countryside. Trace the differences on paper or in a computer to animate the changes and make them easy to see.
  
• What kinds of shellfish live on your beach? Look for dead shells as these will indicate what species live nearby. If there is an ancient Maori midden site near your beach you might look at the species they collected from the beaches years ago and compare them with shells that are present now. Do not disturb the midden, however, simply look at the shells on the surface. Is the midden marked on Department of Conservation maps? If not, you can notify them of its existence. Does the local Iwi know of the midden?
  
• Use a good shell identification book to help you identify the shells and other creatures. Plan a systematic search for living shells, looking in likely and unlikely places. If you see holes in the sand, you might have to dig 10-15 cm down to find the clams. Perhaps you can take an experienced clam digger with you. Look for big shells and baby shells.
  
• Shellfish live in groups, called beds. When you find a bed, sketch its boundaries on the map and note the kind of habitat the particular species likes in the Beach Keeper Log Book. (How can you be sure they are in the right place on the map? Will you use bearings, landmarks, triangulation?).
  
• What other features of the beach can you map? Is there algae growing on the sand or rocks? What kind of algae is it? Some algae, like green sea lettuce, is considered a possible indicator of pollution. Are there crabs? Where are they located and what do they feed on?
  
• Once you have a good map of the beach and some knowledge of the shellfish, you are ready to begin your shellfish census.