Size matters when it comes to the survival of transplanted yellow gorgonian fragments

The yellow gorgonian Eunicella cavolini is a Mediterranean endemic coral. Mediterranean populations underwent sharp decreases in the last decades due to climatic anomalies. In the meanwhile, populations in the Sea of Marmara thrive under conditions exempted from significant thermal variations thanks to the peculiar ocean-ography of the basin. However, they are vulnerable to anthropogenic activities, such as fishing, coastal con-structions, dredging and landfilling. Major infrastructure projects at two remote islands, Yassiada and Sivriada, put healthy gorgonian communities at risk. We observed many dead colonies when Yassiada was constructed and before operations commenced on Sivriada, we transplanted gorgonian fragments 13 km away to a site at lower risk from construction. The transplantation site already hosts yellow gorgonian as sparse colonies; but also, it sits within an important fishing area, and entangled nets over rocks are common. Therefore, together with a local NGO, we initiated conservation efforts simultaneously with the transplantation works. 300 gorgonian fragments in the 4.5-15.4 cm size range were transplanted in two years (2017 - 2019). At six months, the survival of the colonies was significantly size dependent. Fragments of 10 - 15.4 cm initial sizes had the highest survival rate (up to 90 %), while small fragments yielded substantially lower survival. Despite severe impacts from fishing nets and mucilaginous entanglement, 50 % of fragments larger than 10 cm survived after 4.5 years of plantation. Besides, several recruits were observed among 4.5 years old transplants. Therefore, when restoration by raw transplantation actions is planned for gorgonians with thin scleraxis, a minimum fragment size of 10 cm is recommended. The study was a notable example of science/NGO collaboration with substantial local conser-vation success by using extensive media coverage of conservation efforts as leverage to declare the recipient area as a Marine Protected Area.