They propose a measure to mitigate the advance of the invasive anemone that affects the seabed of towns in Los Lagos

Camila Muñoz Gonzalez, Journalist.- Invasive species are one of the main causes of biodiversity loss on the planet, also generating important negative effects on productive sectors, infrastructure and people’s health.

According to what was reported by the Ministry of the Environment, the possibility of a successful biological invasion depends on three groups of conditions. In the first place, of the characteristics of the exotic species (invasiveness of the species); secondly, the state or susceptibility of the receiving ecosystem (invasibility of the site); and, finally, the intensity or number of exotic individuals that are arriving, that is, what is known as propagule pressure.

In the case of the anemone Metridium senilenative to the northern hemisphere, has been classified as an invasive species on the Chilean coast due to its high aggressiveness.

Moreover, this species is responsible for the occupation of large areas of benthic substrate, which in turn is a threat to commercially important species such as sea urchins.

In Carelmapu, a fishing town located in the Los Lagos Region -one of the study areas of the Fisheries Research Program of the Puerto Montt Headquarters of the Austral University of Chile- its coverage has increased from 5% in 2016 to 50% approximately in 2021.

Its high competitive hierarchy is based on its rapid proliferation by fragmentation of its basal disc (asexual reproduction) and its aggressiveness, since it has been reported that it uses its specialized tentacles that can even harm other anemones.

It has also been observed that M.senile she ‘suffocates’ most of the new recruits by sliding over them with her pedal disc, killing all other occupants and thus generating increased free space which is then occupied by her.

Faced with this reality, together with the fishing communities associated with the FIPA project N°2021-36 «Study of the ecology, management and management of the sea anemone of the genus Metridium in the localities of Maullín and Carelmapu in the Los Lagos Region”, it was proposed -as a possible mitigation measure- to evaluate the option of repopulating with mussels and other mussels to generate alternative substrate.

Why was it decided to mitigate by repopulating with mussels?

The mussels or “mussels” are bivalve molluscs known as ecosystem engineers, since they aggregate on the bottom or marine benthos to provide substrate and protection to other species; and as primary colonizers of hard and filamentous substrates in estuaries and coastal areas.

Southern Chile has a rich diversity of mussels that are important habitat formers, making them a real option for restoring exploited shoals. For example, it has been reported that associated with banks of Aulacomya atra (“cholga”) more than 100 different species have been recorded.

Faced with this alternative, the ASTIMAR Shipyards Union of Artisanal Fishermen (Maullín) asked the Undersecretary of Fisheries and Aquaculture to authorize a restocking experiment in the benthic resource management area called Lenqui Punta Santa Teresa, in the Los Lagos Region, following the regulations referred to in the Fisheries and Aquaculture Law and its respective regulations.

After the formal review and approval, both the UACh Fisheries Research Program team and the ASTIMAR fishermen proceeded to implement three 5x5M quadrats covered with mussels (A. behind preferably), which were acquired in farming centers and were transferred to the Shipyard area in their respective farming lines.

There, underwater filming was carried out, which will be repeated to monitor the experiment.

For now it is expected that M.senile compete with mussels, since due to its ability to move it could colonize the substrate of mussel shells. In addition, considering that the mussels form a complex substrate, it is expected that throughout the sampling period other species can colonize the “new substrate”, including the settlement of new benthic species.

During the project, it will be evaluated to continue monitoring this experience at least twice a year for the next 36 months, in case the mussels persist.

References

• Borthagary, AI & A. Carranza 2007. Mussels as ecosystem engineers: Their contribution to species richness in a rocky littoral community. Oecol Act. 31:243-250.
• Buschbaum, C., S. Dittmann, J. Hong, I. Hwang, M. Strasser, M. Thiel, N. Valdivia, S. Yoon & K. Reise. 2009. Mytilid mussels: global habitat engineering in coastal sediments. Heligoland Mar. Res. 63: 47-58.
• Carranza A., Defeo O., Beck M., Castilla JC (2009) Linking fisheries management and conservation in bioengineering species: the case of South American mussels (Mytilidae). Reviews in Fish Biology and Fisheries, 19, 349–366.
• Nelson ML, Craig SF. 2011. Role of the sea anemone Metridium senile in structuring a developing subtidal fouling community. Mar Ecol Prog Ser 421:139-149. https://doi.org/10.3354/meps08838
• Purcell, JE 1977. The diet of large and small individuals of Metridium senile. Bull. S. Cal. Acad. Sci. 76, 168-172.
• Sebens, K. 1985. The Ecology of the Rocky Subtidal Zone. American Scientist-AMER SCI. 73. 548-557. Silva et al. 1998.
• Sepulveda RD, Camus PA, Moreno CA 2016. Diversity of faunal assemblages associated with ribbed mussel beds along the South American coast: Relative roles of biogeography and bioengineering.
• https://especies-exoticas.mma.gob.cl/