Moving away from synthetic materials used at FADs: evaluating biodegradable ropes’ degradation

The present study summarizes the results of a project to test biodegradable ropes, to be used at FADs, in a controlled environment. Three types of biodegradable ropes were tested following their evolution for one year at sea: (i) twisted 100 % cotton rope; (ii) twisted 50% cotton and 50% sisal rope; and (iii) cotton, sisal and linen rope with loops. Samples were deployed in June 2016 in 2 different sites simultaneously, in offshore waters attached to a mooring rope, simulating a FAD in oceanic waters and in a shallow lagoon close to the reef in Maniyafushi island, simulating the arrival of a FAD to the coast. Results show different robustness of the ropes, being the strongest the one made of sisal and cotton. Other considerations for the successful use of biodegradable ropes at FADs are discussed.