How to do a Barnacle Survey
First identify the species of barnacle you are going to survey. We are interested in looking at the
species Austrominius modestus and Semibalanus balanoides. It can be difficult to separate these two
species apart as they both occupy the same habitats, especially juveniles as these are yet to develop
the main distinguishing features. The most important identification feature of these barnacles is the
number of shell plates.
Key identification features:
ID characteristics
Austrominius modestus
Semibalanus balanoides
Number of shell plates
4
6
Size
Up to 10mm diameter
Up to 10mm diameter
Aperture
Diamond shaped with a smooth
straight split between the
opercular plates
Diamond shaped with an obvious
step in the split between the
opercular plates
Appearance
Greyish/white to greyish/brown,
Rough, wavy edge in adults
White/cream to grey/brown,
smooth, less wavy edge in adults
Next, you will need to decide on what size quadrat you will use for the survey. We advise a 5cm X
5cm quadrat to be used as this is not too large an area for counting the small cyprids within it.
Quadrats can be made out of anything if you do not have one to hand. Just pieces of card with the
square cut out will work fine but be careful you do not get this wet. If you do plan on making one
then any reasonable sized lid from a plastic container/yoghurt pot etc. will work well. For estimating
the percentage of barnacle cover on the shore, you may choose to use a bigger quadrat. A 10cm x
10cm quadrat is the biggest we recommend. It is important if you do make one keep them as square
as possible.
Quadrat Templates:
Use this sheet to cut out the template and help you make your own quadrat.
5cm X 5cm
10cm X 10cm
Shore height selection
Once you have selected your site for the survey, you must determine a vertical gradient in the
intertidal zone. This is the zone where the tide covers the shore during its daily cycle. This zone can
now be split into three separate zones called, High shore, Mid shore and Low Shore which are
recognisable by the species of algae which can be found growing within them.
High Shore:
The area from the highest tidal line to the starting point where the species Fucus vesiculosis or
Bladder Wrack begin to grow. This high shore zone will: contain the majority of Pelvetia canaliculata
or Channel Wrack cover; have some barnacle cover over bare rock above P. canaliculata and
possibly some Lichen will be present at the highest point of the tide line.
Lichen
Pelvetia canaliculata
Fucus vesiculosis
Mid Shore:
The area between the start of the species Fucus vesiculosis up until the start of the species Fucus
serratus or Serrated Wrack. Within the mid shore zone the species Ascophyllum nodosum or Egg
Wrack is the dominant algae species. This zone can also cover the largest area on the shore.
Ascophyllum nodosum
Fucus serratus
Low Shore:
Any area which is below the start line where the species Fucus serratus appears. Expect to find a
large quantity of this alga along with some larger kelp species such as Laminaria digitata (below)
growing.
Quadrat placement and sampling:
Once you have determined your zones on the rocky shore you can start taking quadrat samples of
the barnacles. To do this you need to locate the midpoint within each zone, one zone at a time.
When using a quadrat we tend to perform a random throw technique so every sample is equal and
does not create any bias in our sampling effort by selecting where to place the quadrat. Random
sampling can be done in a variety of ways but the easiest and quickest will be to either close your
eyes and throw the quadrat onto the shore, or throw it over your shoulder. Where it lands is where
you should take the sample. If however the quadrat lands in an unsuitable place, for example in a
rock pool where the effects of the seawater creates micro habitats, then the quadrat should be
thrown again.
With each quadrat you thrown in each of the three zones you should record your data as accurately
as you can on the data recording form. Refer to the form for how many quadrats you need to take
and what data is collected and recorded for a Barnacle Survey.
Barnacle Survey data:
Cyprid settlement number:
Within each quadrat (5cm X 5cm) count the number of newly settled cyprid larvae that have just
attached during the previous high tide. This can only be done during the settlement season which is
between March to August. The later in the year the survey the less settled cyprids you will find. The
best time to go will be the months April and May as this is when high concentrations of cyprids are in
the water column waiting to find a place to settle. For more information on settlement, check out
the www.marinelarvae.org website.
Juvenile Barnacles:
Using the 5cm X 5cm quadrat count the numbers of juvenile barnacles present in each throw. These
are the ones which have recently metamorphosed from cyprid larvae into juveniles. Juveniles tend
to be much lighter in colour than older individuals and will be the smallest ones in the quadrat. By
getting an accurate count of juveniles that have settled that season we can understand how
successful the settlement of cyprids has been.
Percentages of adult and juvenile barnacle cover:
The 10cm X 10cm quadrat is better for this data collection as it covers a greater area. Estimate how
much of the rock within each quadrat is covered by both the adult and juvenile barnacles. This type
of data allows us to estimate how much of the shore is utilised by barnacles and how much free
space there is in each zone for new recruits. These estimations can be done any time of the year on
any rocky shore where you find the species of barnacles we are interested in surveying.
Once you have done your own barnacle survey don’t forget to fill in the
Barnacle Survey Form and send it onto the team at www.marinelarvae.org,
we are looking forward to your data!