Evaluating potential biodegradable twines for use in the tropical tuna fishery [Also published as IATTC 2016 SAC-07-INF-C(h)]

Tens of thousands of man-made drifting FADs are estimated to be in use by industrial purse seiners worldwide. Although FAD fishing is considered a successful and efficient method to catch tropical tuna, it accounts for several ecological and environmental drawbacks, such as producing larger amount of by-catch compared to free school fishing, potentially increasing the amount of marine debris, or unintentionally entangling individuals of some vulnerable species, like sharks or turtles. Indeed, the latest is considered an important concern by RFMOs and fleets have already started to regularly deploy non-entangling DFADs during their commercial trips. However, the use of new materials to construct the underwater part of the DFAD has not been explored in detail so far. In order to face this situation, scientists, industry, and twine manufacturers have worked in collaboration to test and evaluate different potential biodegradable materials that can be used in the FAD fishery. This paper presents first results of a recent research conducted in the Atlantic Ocean dealing with new materials and designs of twines for use in the DFAD construction to prevent the entanglement of sea turtles and sharks, being as much as biodegradable as possible and as efficient in aggregating fouling as the traditional one. Results show that different materials and designs degrade differently over the study period and that material specific characteristics play and important role in the lifetime of the twines. The use of new and promising materials and designs are discussed, as well as its implications for conservation and relevant future lines of investigation.