individuals (>20 mm total shell length). This class-size represents 33% of the total
number of individuals. The estimation of biofouling of artificial rocky substrate via
image treatment using the software ENVI revealed a percentage of coverage by the
alien invasive mussel oscillating between less than 10 to 90 % (Figure 1). The invasion
of B. pharaonis reasonabily displaced the native mussel M. galloprovincialis. Indeed,
this species occurred in the past with high densities, whilst no M. galloprovincialis were
found during the present study. All the respondents (32 fishers) reported a decline of
about 30 % in their income as a consequence of the disappearance of M.
galloprovincialis. Such cases of displacement of native Mediterranean Mytilid had
already been reported with Mytilaster minimus as a consequence of the invasion of B.
pharaonis (Safriel & Sasson-Frostig, 1988; Rilov et al., 2004). We conclude that the
invasivion of B. pharaonis has dramatically changed the structure of native rocky shore
assemblages in the Tunis Southern Lagoon.
Fig. 1: Spatial coverage (%) of rocky artificial shores of Tunis Southern Lagoon by B.
pharaonis (April 2022)
Bibliography
RILOV G., BENAYAHU Y., GASITH A. (2004) - Prolonged Lag in Population Outbreak of an
Invasive Mussel: A Shifting-Habitat Model. Biological Invasions, vol.6: 347–364.
SAFRIEL U.N., SASSON-FROSTIG Z. (1988) - Can colonizing mussel outcompete indigenous
mussel? Journal of Experimental Marine Biology & Ecology, 117 (3): 211- 226.
SARÀ G., DE PIRRO M. (2011) - Heart beat rate adaptations to varying salinity of two
intertidal Mediterranean bivalves: the invasive Brachidontes pharaonis and the native
Mytilaster minimus. Italian Journal of Zoology, 78 (2): 193- 197.
10-30%
30-50%
50-70%
70-90%
<10%
Radès channel
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
126
number of individuals. The estimation of biofouling of artificial rocky substrate via
image treatment using the software ENVI revealed a percentage of coverage by the
alien invasive mussel oscillating between less than 10 to 90 % (Figure 1). The invasion
of B. pharaonis reasonabily displaced the native mussel M. galloprovincialis. Indeed,
this species occurred in the past with high densities, whilst no M. galloprovincialis were
found during the present study. All the respondents (32 fishers) reported a decline of
about 30 % in their income as a consequence of the disappearance of M.
galloprovincialis. Such cases of displacement of native Mediterranean Mytilid had
already been reported with Mytilaster minimus as a consequence of the invasion of B.
pharaonis (Safriel & Sasson-Frostig, 1988; Rilov et al., 2004). We conclude that the
invasivion of B. pharaonis has dramatically changed the structure of native rocky shore
assemblages in the Tunis Southern Lagoon.
Fig. 1: Spatial coverage (%) of rocky artificial shores of Tunis Southern Lagoon by B.
pharaonis (April 2022)
Bibliography
RILOV G., BENAYAHU Y., GASITH A. (2004) - Prolonged Lag in Population Outbreak of an
Invasive Mussel: A Shifting-Habitat Model. Biological Invasions, vol.6: 347–364.
SAFRIEL U.N., SASSON-FROSTIG Z. (1988) - Can colonizing mussel outcompete indigenous
mussel? Journal of Experimental Marine Biology & Ecology, 117 (3): 211- 226.
SARÀ G., DE PIRRO M. (2011) - Heart beat rate adaptations to varying salinity of two
intertidal Mediterranean bivalves: the invasive Brachidontes pharaonis and the native
Mytilaster minimus. Italian Journal of Zoology, 78 (2): 193- 197.
10-30%
30-50%
50-70%
70-90%
<10%
Radès channel
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
126