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Monitoring programme design

Standard monitoring protocols for marine invasive alien reached in each transect. In the second stage (during the
species in MPAs with examples of work conducted in ascent), the divers will carefully examine each of the
protected areas benthic communities found for approximately ten minutes
to detect the presence or absence of possible invasive
There is a variety of monitoring methods and programmes and/or alien species. If an alien species is found, its relative
operating in MPAs, but few of them are specifically abundance should be estimated. This may be performed
designed to monitor alien species and marine invasive by using semi-quantitative methods such as the Braun
alien species. Monitoring the abundance and distribution Blanquet scale.
patterns of alien species, particularly those that are
invasive in nature, will help us to detect problems early,
understand the relative risk of invasions by different
species into MPA environments, identify the potential Braun Blanquet cover-abundance scale
patterns of invasions and see how to target management
Braun-Blanquet scale Range of cover (%)
efforts so as to reduce further risks. The spatial and habitat
distribution of a given IAS can further provide useful 5 75-100
information to help identify which areas are most at risk of 4 50-75
being invaded in the future.
3 25-50
A monitoring programme must cover all stages of 2 5-25
assessment, be simple, and record the presence and 1 <5; numerous individuals
status of different species, through a science-based
+ <5; few individuals
approach. It can also take advantage of existing
programmes in the MPA in which specialist teams monitor
native species diversity, and it can also use trained
volunteers (such as recreational diving club members)
specially to report sightings in new areas or of new
species. A similar procedure could be followed when an invasive
species is detected. If it is feasible during the same dive, its
Underwater visual surveys abundance should be recorded in each habitat. Taking
photographs of unidentifiable species or potential biological
To monitor the occurrence and spatial distribution of invaders can be a valuable aid to confirm identification.
invasive species inside an MPA, a series of sampling
stations should be selected beforehand. These stations On more level substrates, monitoring can be performed
should be chosen to be representative of all the habitats, along transects 25 m long and 5 m wide at each station.
depth ranges, substrates and wave exposure conditions Along each transect, the divers should swim in one direction
found in each individual MPA. The number of sampling at constant speed, identifying and recording the presence
stations will therefore be variable and will depend on the of each alien species encountered. To record the spatial
MPA’s size and habitat heterogeneity as well as the distribution and density of different taxonomic groups, a
logistical and financial facilities available. variety of standard methodologies can be used. This work
can be conducted during a second visit to the area.
The monitoring, conducted by two scuba divers, should
follow linear transects perpendicular to the shore and it
should be run twice a year in summer and winter to detect
the presence of alien species of seasonal occurrence. If
that is not possible due to logistical or financial
constraints, the monitoring should be run at least once a
year, preferably in summer, and at the same time each
year. Perennial plant species display their greatest growth
over summer making them easier to detect at this time.

On vertical walls and steep slopes, monitoring can be
undertaken in two stages (Fig. 12). The first stage (during
the descent) will serve to identify the main topographic and
bathymetric features and the succession of habitats at
different depths from the surface to the deepest zone Monitoring species. Photo: L. Tunesi

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