Recovery capability of the tall sea pen Funiculina quadrangularis after fishing ban in the Adriatic Sea

The tall sea pen Funiculina quadrangularis is considered vulnerable in the Mediterranean Sea and critically endangered in Italy. In this study we monitored a F. quadrangularis population off Tremiti Islands (Italy, Adriatic Sea) initially impacted by trawl fishing, then affected by the laying of a submarine cable and the subsequent ban of fishing activities. Despite the cable laying causing a sudden depletion of the population, F. quadrangularis showed promising recovery after the trawling ban. Its density increased by 466 %, from 0.0047 colonies m^-2 under trawling pressure to 0.0266 colonies m^-2 after a two years-long fishing ban. An overall increase in both mean and maximum rachis size was recorded (41 % and 54 %, respectively), with a more structured population. Positive signs of recovery were also detected on several associated species, including some of both conservation and commercial importance. Marine litter increased throughout the two years of the fishing ban, possibly due to the lack of removal by trawl nets. Although the installation of an underwater cable may represent an indirect measure of conservation due to the trawl fishing ban, ad hoc initiatives aimed at preserving sea pen fields are needed. Given the recovery capability of F. quadrangularis, conservation actions may yield positive results in a shorter-than-expected time frame.