teaching
notes 4 - organising mini-beast sampling trips
Notes for group leaders and students
Organising
the field trip
Selecting a suitable river or stream for habitat sampling should
be a joint activity between the teacher or group leader and pupils.
The chosen site should be pinpointed on a map and a grid reference
taken before the visit. The river, place name and nearest town must
be recorded and permission must be gained from the landowner before
the trip. The section 'Reducing
Risk on a Field Trip' (T2) is designed as a guideline
for teachers. 'Safety First'
(T3) should be read by students before the trip.
When
to go scuffle/kick sampling
Timing is important, scuffle/kick sampling should not be undertaken
between October and May as it is the fish spawning season (F02)
and the eggs could be crushed underfoot. Only sample from the bank
at that time of year using a throw net or dipping net.
Equipment
You will need the following items of equipment:
• Nets
• Trays: White plastic trays are best or, if not, coloured
trays with white card in the bottom
• Indicator papers: These test acidity (pH) and concentrations
of nitrates
• Extras: Although not essential, the following can be very
useful:
Plastic spoons - to pick up animals for closer inspection
Small paint brushes - as above if you can't get them with the spoon
Hand lens - useful for identification and also for seeing how spectacular
some of the creatures really are
• Clothing: Wellington boots; jerseys and waterproof gear;
spare socks; towel. You must be properly dressed and prepared for
a worsening of the weather.
METHOD
a) Where to go sampling
The scuffle sampling site should be a shallow, stony part of a river
or stream. Such areas are known as riffles. Shallow means less than
wellie-depth! A variety of stone sizes is best, say from about marble-size
to tennis ball size. Check that permission has been granted to take
samples in this part of the river.
b) Taking
the sample
Most animals live among the stones where they won't be washed away
so the sampling method will need to disturb the stream bed. The
best method is the scuffle method. This involves disturbing the
stream bed with a twisting or shuffling motion of the feet, moving
slowly backwards in an upstream direction with the net virtually
in front of you. The top edge of the net should just rest on the
bed. In this way any animals dislodged by the motion of your feet
will leave the stones and be swept into the net by the current.
If there is too little current you may need to move the net from
side to side to improve your catch. Make sure that someone is behind
you watching that you don't trip up.
c) How
many samples?
You should take three one-minute samples. Your party could divide
up into three smaller groups and each take one sample. You could
also split up the responsibilities within each group with one person
taking the sample, one person timing it, one person making sure
the sampler doesn't fall over, and so on.
But why three samples? Well, one sample may be a poor one (the bit
of stream you choose may have been recently disturbed) and two samples
could be widely different. Three samples, therefore, is the least
number which should give you reliable results.
d) What
if it isn't stony?
It may mean walking some way along the bank to find a suitable spot.
Some areas may not have ideal sampling conditions. Try and avoid
muddy riverbeds, but if it is all you can find, sample from the
bank, using the net to disturb the mud surface.
You may find areas you want to sample have only large rocks or boulders.
In this case, select a number you can lift easily and gently rub
them while holding them in the mouth of the net. In this way, animals
clinging to the rocks will be washed in. Carefully replace the rocks.
Record how you sampled.
e) Looking
for animals
Gently swish the net in the water to get rid of any mud in the sample.
Half fill your tray(s) with undisturbed water and gently empty the
contents of the net by turning it inside out in the tray. Most of
the animals will swim out on contact with the water. Make sure all
the animals have been removed and led the contents of the tray settle.
Then look for movement - what's swimming, what's crawling, what's
gliding along the bottom or looping from stone to stone. Use the
Mini-beast Identification Sheet (B06b) to identify what is present.
f) Recording
what you find
The exact method of recording will be explained by your teacher
or leader. If you are using the Mini-beast Biodiversity Survey Sheet
(B06c) the main purpose
is to record how many different types of creatures you have found.
You may also be asked to give some idea of how many animals there
are of each type - a few (1-3); some (4 -14); a lot (more than 10;
masses (more than 100). If required, these estimates will give valuable
further information for analysing the results.
g) Returning
the sample
Gently return the contents of the trays to the part of the stream
from which you obtained the sample. Roll back any large stones that
have been disturbed. Try and leave the site as you found it.
WATER
QUALITY
• Indicator species: The presence of some types of mini-beast
can indicate the quality of the water. Each type of animal has been
given a value indicating the extent to which it requires good quality
water. For example, Stonefly nymphs need very clean, well-oxygenated
water and score 10; Sludge worms can live in polluted mud and score
1. This doesn't mean that you might not find worms in quite clean
water but they are not clean water indicators. On the Mini-beast
Identification Sheet (B06b)
each creature is given a 'value' after their name in brackets and
those that are particularly useful indicator species have a star
*.
• Other indicators: There are also some other clues to look
out for such as kingfishers, dippers and sandmartins. They tell
you something about the water because they feed on the animals that
live in it. The presence of otters is a good sign too, not only
is the site undisturbed but large fish are probably present indicating
good water quality. Blanketweed and sewage fungus on the other hand
are bad signs, indicating organic pollution - don't sample.
• Chemical testing: There are some chemical tests which can
tell you about the state of the water. You can use pH indicator
strips to measure the acidity (pH) of the water and nitrate indicator
strips to measure the concentration of nitrates.
Acidity: if the water is acid (less than pH7) it does not necessarily
mean it is polluted. Many of the rivers and streams in the South
West are naturally acidic because of the type of surrounding rocks
and vegetation. These river and streams can be easily damaged if
real acid pollution comes along because they can't absorb its effects.
Nitrates: Nitrates are chemicals which plants need and are often
found in fertilisers. High concentrations of these nitrates are
sometimes found in farming areas where large amounts of fertilisers
are used. High nitrate levels have been linked with certain diseases.
They also fertilise the water causing it to become choked with weed
and clouded with tiny suspended plants called algae.
• Results: Both chemical tests and using animals and plants
as indicators have advantages and disadvantages and you can probably
work out by now what some of them are. A good reason for using indicator
species to test the quality of the water is that animals and plants
are the real customers of our water systems - if they don't like
the conditions, they disappear!
• Taking measurements: You can calculate the speed of the
water by timing how long a twig takes to travel 2 metres in the
water. Divide 2 by the number of seconds to get the speed in metres/seconds.
The depth of water should also be measured where you sample.
CONDUCT
During a field trip think of other users: The site at which you
will be sampling will always have other uses other than fieldwork!
Be careful that your activities do not interfere with others.
Respect ownership: You have no statutory right of access to most
land. When you are given permission to carry out work on someone's
land, make sure you respect his or her wishes.
Encourage respect for fieldwork: Show your intention is serious
and reflect this in the way the group behaves. If you have a vehicle,
be careful it does not cause an obstruction. Follow the Country
Code.
Leave the area as you found it: Try to keep your movements to a
minimum so as not to damage the area. Especially take care not to
walk on crops or to damage the banks of the river. Do not take specimens
home - they will only die and it may be illegal.
Choose your area carefully; If you intend to continue your fieldwork
at other sites (and you are encouraged to do so), try to avoid areas
that are intensively used by field parties. Too much disturbance
from visitors can reduce the value of the site for fieldwork. If
in doubt, consult the Local Trust for Nature Conservation.
Avoid disturbing plants and animals and the unnecessary collection
of specimens: Keep the number of samples taken to a minimum and
always return specimens to the same location from where they came.
If you turn over stones to look for animals, turn them back again.
Flowers, plants, mosses and lichens should not be taken.
CONSERVATION
These surveys and sampling expeditions are about conservation -
often described as the wise management of the planet's resources.
If you follow the guidelines given above, there will be little damage
to the environment and no one, not even the plants and animals,
will regret your visit. You will have been involved in conservation,
enjoyed the environment and learnt a great deal.
|
