were monitored by citizens and sea users. Reports of the presence of mytilid were
subsequently verified using photos and videos sent to the authors.
Results
Our studies show that B. pharaonis is currently present in at least 7 locations in Tunisia
as follows: Gammarth beach (in 2020 with low density), Bizerte lagoon (in 2021 with
Low density), Tunis Northern lagoon: Berges du lac and Kheireddine canal (in 2022
with high density), Boughrara port (in 2022 with very high density), Djerba island: from
Ajim in the southwest to the Roman road in the southeast (in 2022 with very high
density). In addition, via the citizen science group TunSea two reports on the presence
of B. pharaonis on the lines of structures of the aquaculture facility in Bni Khiar (in
2021 in low density) and Ghannouche beach (in 2022 in low density) (Fig 1).
Fig.1: B. pharaonis on the lines of structures of the aquaculture facility
Discussion and conclusions
This study based essentially on citizen science highlights that B. pharaonis continues its
expansion (up to the Bizerte lagoon, the northernmost point at the moment). Regarding the
various locations of occurrences, of ecosystems such as lagoons, ports and the distance
between surveyed localities, this suggests that the introduction could probably occurs through
these vectors: aquaculture (Bni Khiar), ballast water and shipping transport (Bizerte lagoon),
fouling (boats, beings live), floating debris (Ghannouche beach stranding). The highest
density was observed in Djerba (Ajim) covering all rocks of the intertidal zone and forming
large beds. Density exceeding 10,000 individuals per square meter, twice as high compared to
observations of Hamza et al. in 2019. In Tunis Southern Lagoon, B. pharaonis density was
increasingly high going towards the lake, suggesting that this mollusc prefers sheltered areas.
These observations agree with those of Safriel et al. (1980). B. pharaonis may aggressively
overrun additional Tunisian areas in the future, threatening indigenous bivalve species such as
the native Mytilaster minimus and leading to economic losses if it reaches the shellfish
facilities of Bizerte lagoon that would be unable to compete with B. pharaonis in terms of
density. This species should be upgraded to invasive non-indigenous species, be a priority for
monitoring, and be included in Tunisia's national biodiversity monitoring program.
References
HAMZA A., ENAJJAR, S., KARAA S., BRADAI M.N. (2018) - record of the invasive red sea
mussel Brachidontes pharaonis (bivalvia: mytilidae) from the lagoon of Boughrara
(Southern Tunisia, central Mediterranean Sea). Bulletin de I’INSTM Salammbô, 5-8.
OUNIFI BEN AMOR, K., RIFI, Μ., GHANEM, R., DRAIEF, I., ZAOUALI, J., BEN
SOUISSI, J. (2016) - Update of alien fauna and new records from Tunisian marine waters.
Mediterranean Marine Science, 17(1), 124-143.
SAFRIEL U.N., FELSENBURG T., GILBOA A. (1980) - The distribution of Brachidontes
variabilis (Krauss) along the Red Sea coasts of Sinai. Argamon, 7(3):31-43.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
92
subsequently verified using photos and videos sent to the authors.
Results
Our studies show that B. pharaonis is currently present in at least 7 locations in Tunisia
as follows: Gammarth beach (in 2020 with low density), Bizerte lagoon (in 2021 with
Low density), Tunis Northern lagoon: Berges du lac and Kheireddine canal (in 2022
with high density), Boughrara port (in 2022 with very high density), Djerba island: from
Ajim in the southwest to the Roman road in the southeast (in 2022 with very high
density). In addition, via the citizen science group TunSea two reports on the presence
of B. pharaonis on the lines of structures of the aquaculture facility in Bni Khiar (in
2021 in low density) and Ghannouche beach (in 2022 in low density) (Fig 1).
Fig.1: B. pharaonis on the lines of structures of the aquaculture facility
Discussion and conclusions
This study based essentially on citizen science highlights that B. pharaonis continues its
expansion (up to the Bizerte lagoon, the northernmost point at the moment). Regarding the
various locations of occurrences, of ecosystems such as lagoons, ports and the distance
between surveyed localities, this suggests that the introduction could probably occurs through
these vectors: aquaculture (Bni Khiar), ballast water and shipping transport (Bizerte lagoon),
fouling (boats, beings live), floating debris (Ghannouche beach stranding). The highest
density was observed in Djerba (Ajim) covering all rocks of the intertidal zone and forming
large beds. Density exceeding 10,000 individuals per square meter, twice as high compared to
observations of Hamza et al. in 2019. In Tunis Southern Lagoon, B. pharaonis density was
increasingly high going towards the lake, suggesting that this mollusc prefers sheltered areas.
These observations agree with those of Safriel et al. (1980). B. pharaonis may aggressively
overrun additional Tunisian areas in the future, threatening indigenous bivalve species such as
the native Mytilaster minimus and leading to economic losses if it reaches the shellfish
facilities of Bizerte lagoon that would be unable to compete with B. pharaonis in terms of
density. This species should be upgraded to invasive non-indigenous species, be a priority for
monitoring, and be included in Tunisia's national biodiversity monitoring program.
References
HAMZA A., ENAJJAR, S., KARAA S., BRADAI M.N. (2018) - record of the invasive red sea
mussel Brachidontes pharaonis (bivalvia: mytilidae) from the lagoon of Boughrara
(Southern Tunisia, central Mediterranean Sea). Bulletin de I’INSTM Salammbô, 5-8.
OUNIFI BEN AMOR, K., RIFI, Μ., GHANEM, R., DRAIEF, I., ZAOUALI, J., BEN
SOUISSI, J. (2016) - Update of alien fauna and new records from Tunisian marine waters.
Mediterranean Marine Science, 17(1), 124-143.
SAFRIEL U.N., FELSENBURG T., GILBOA A. (1980) - The distribution of Brachidontes
variabilis (Krauss) along the Red Sea coasts of Sinai. Argamon, 7(3):31-43.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
92