engleski

Experimental exposure of tunicate Clavelina oblonga to reduced salinities as a possible eradication measure of invasion in mussel mariculture

A new invasive species of tunicate was observed in summer 2020 in mariculture on the western and eastern coast of Istria, Croatia. After field inspection it was confirmed that the identified species is invasive tunicate Clavelina oblonga Herdman, 1880 (Ascidiacea, Enterogona, Clavelinidae) previously recorded in the Gulf of Trieste and Piran in 2015. Due to its fast growth, C. oblonga outgrows and overgrows mussels, physically restricting their growth and feeding, and increasing the weight on loadbearing infrastructure. This species is described as sensitive to lowered salinity. Cultivators in Lim bay have a known practice of transferring their mussels to the beginning of the bay, exposing them to brackish waters in order to reduce overgrowth. During an experimental laboratory exposure of C. oblonga to different salinities for a period of 14 days, followed by 14 days recovery, no sexual reproduction was noted, while sea water salinities 20 and 11 caused disruption in food uptake and digestion which led to change of colour, tissue necrosis and finally body fragmentation. Based on our preliminary research, field observations and available literature we assume and conclude that translocation of mussel holding nets with tunicates C. oblonga overgrowth to locations of lower sea water salinity (<20) for 7-10 days, can be a natural and effective way/measure for eradication of this invasive species.

Clavelina oblonga ; salinity ; mussel ; mariculture

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