Gori A., Gili J-M., Linares C. - Institut de Ciències del Mar and University of Barcelona
Gorgonians are one of the main ecosystem engineers in deep Mediterranean bottoms. They generate complex three-dimensional structures that enhance spatial heterogeneity and support a highly diverse associated fauna. Gorgonians are also among the most frequently found taxa in fishing by-catch. Fishing can cause the total removal of the gorgonian colonies (in the case of bottom trawling and long-line fishing) or their partial damage (in the case of trammel net and long-line fishing). These impacts can have long-lasting effects owing to the low growth rates and slow population dynamics of Mediterranean gorgonians. Bearing in mind these life history traits, it is highly desirable to promote active ecological restoration actions in order to facilitate and accelerate their recovery.
Figure 1. Gorgonians on the continental shelf in the north of Cap de Creus (Spain). Photo credits to IFM-GEOMAR - ICM-CSIC.
During the last two years, the ShelfReCover project has explored the viability of the ecological restoration of deep gorgonian populations using a novel approach: gorgonian colonies collected as by-catch by artisanal fishermen were transplanted back in their natural environment. A total of 120 gorgonians were transplanted on three steel landers, each 2 metres in diameter and 120 kg weight. The landers were deployed at 84m depth on the continental shelf in the north of Cap de Creus (Spain). Gorgonian survival after transplantation was monitored by means of the Autonomous Underwater Vehicle (AUV) Girona 500, working as Hybrid Remotely Operated Vehicle (HROV). A sonar reflector located at on each lander enabled their easy relocation using the AUV sonar. Subsequent surveys showed that most of the gorgonians had survived (100% at 6 months and 93% at 12 months after the landers were deployed).
Figure 2. One of the landers with the transplanted gorgonians, during its deployment (left) and on the seabed at 84 m depth (right). Photo credits to CIRS – UB
These preliminary results highlight the viability of deep gorgonian recovery and transplantation in their original habitat. Based on these results the Institut de Ciències del Mar (ICM-CSIC) and the Universitat de Barcelona are evaluating in the MERCES project the viability of large spatial scale actions for the restoration of deep-water gorgonians on the Mediterranean continental shelf to mitigate fishing impacts.
For further information contact Andrea Gori and Josep-Maria Gili, Institut de Ciències del Mar, Barcelona (firstname.lastname@example.org), or Cristina Linares, Universitat de Barcelona, Barcelona (email@example.com)