Managing tropical tuna purse seine fisheries through limiting the number of drifting fish aggregating devices in the Indian Ocean: food for thought

Summary This paper deals with the use of drifting fish aggregating devices (DFADs) in the Indian Ocean and of the potential interest to manage purse seine fisheries through limiting their number. Potential risks associated with a massive use of DFADs are first discussed. Based on new information on the numbers of DFADs released by the French fleet in the 2003-2014 period, this paper estimates the levels and trends of the total numbers of DFADs deployed and active at-sea. It is estimated that the total number of DFADs numbers has been increasing by about 70% since the early 2000s and that they could reach 10,500-14,500 nowadays. A good knowledge of the total numbers of DFADs is urgently needed to better estimate the fishing effort and capacity of purse seine fisheries. Future limitations in the number of DFADs could be a direct and efficient way to reduce fishing effort exerted by purse seiners and their support vessels. Following a precautionary approach, we suggest that IOTC could consider setting a cap on the number of DFADs drifting at-sea and that threshold reference levels could be based on the year 2013, at least to slow down the trend observed in the overall fishing capacity on DFADs. Such measures should be first carefully analysed by an ad hoc IOTC DFAD multidisciplinary working group to ensure their efficient implementation and to allow an improved sustainability of the concerned fisheries.

[1]  M. Grande,et al.  Reproductive potential of Yellowfin Tuna (Thunnus albacares) in the western Indian Ocean , 2013 .

[2]  Guoping Zhu,et al.  Impacts of fish aggregation devices on size structures of skipjack tuna Katsuwonus pelamis , 2012, Aquatic Ecology.

[3]  M. Grande.  The reproductive biology, condition and feeding ecology of the skipjack, katsuwonus pelamis, in the Western Indian Ocean , 2013 .

[4]  Emmanuel Chassot,et al.  Precision in bycatch estimates: the case of tuna purse-seine fisheries in the Indian Ocean , 2012 .

[5]  David Itano,et al.  Fish behaviour from fishers' knowledge: the case study of tropical tuna around drifting fish aggregating devices (DFADs) , 2007 .

[6]  M. Grande,et al.  Fecundity regulation strategy of the yellowfin tuna (Thunnus albacares) in the Western Indian Ocean , 2013 .

[7]  Patrice Guillotreau,et al.  Fishing tuna around Fish Aggregating Devices (FADs) vs free swimming schools: Skipper decision and other determining factors , 2011 .

[8]  Javier Ariz,et al.  Observed changes in the species composition of tuna schools in the Gulf of Guinea between 1981 and 1999, in relation with the Fish Aggregating Device fishery , 2000 .

[9]  Emmanuel Chassot,et al.  A review of the conservation benefits of marine protected areas for pelagic species associated with fisheries , 2012 .

[10]  C. Roger.  Relationships among yellowfin and skipjack tuna, their prey‐fish and plankton in the tropical western Indian Ocean , 1994 .

[11]  E. Chassot,et al.  MANAGING TROPICAL TUNA PURSE SEINE FISHERIES THROUGH LIMITING THE NUMBER OF DRIFTING FISH AGGREGATING DEVICES IN THE ATLANTIC: FOOD FOR THOUGHT , 2015 .

[12]  Emmanuel Chassot,et al.  Global spatio-temporal patterns in tropical tuna purse seine fisheries on drifting fish aggregating devices (DFADs): Taking a historical perspective to inform current challenges , 2013 .

[13]  Jean-Louis Deneubourg,et al.  Looking behind the curtain: quantifying massive shark mortality in fish aggregating devices , 2013 .

[14]  R. Anderson,et al.  Entanglement of Olive Ridley Turtles Lepidochelys olivacea in ghost nets in the equatorial Indian Ocean , 2009 .

[15]  Mar Ecol,et al.  Drifting fish aggregation devices could act as an ecological trap for tropical tuna species , 2008 .

[16]  Pierre Chavance,et al.  Marine turtle interaction with purse-seine fishery in the Atlantic and Indian oceans: Lessons for management , 2014 .

[17]  Wenjiang Guan,et al.  The Large-Scale Deployment of Fish Aggregation Devices Alters Environmentally-Based Migratory Behavior of Skipjack Tuna in the Western Pacific Ocean , 2014, PloS one.

[18]  Colin W. Clark,et al.  Incentive-based Approaches to Sustainable Fisheries , 2006 .

[19]  E. J. Milner-Gulland,et al.  The past, present and future use of drifting fish aggregating devices (FADs) in the Indian Ocean , 2014 .

[20]  Alain Fonteneau,et al.  A worldwide review of purse seine fisheries on FADs , 2000 .

[21]  Emmanuel Chassot,et al.  Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives , 2014 .

[22]  David Itano,et al.  Behavior of yellowfin (Thunnus albacares) and bigeye (T. obesus) tuna in a network of fish aggregating devices (FADs) , 2007 .

[23]  Jean-Louis Deneubourg,et al.  Comparison of condition factors of skipjack tuna (Katsuwonus pelamis) associated or not with floating objects in an area known to be naturally enriched with logs , 2014 .

[24]  John Hampton,et al.  Natural mortality rates in tropical tunas: size really does matter , 2000 .

[25]  Victor Restrepo,et al.  Is it good or bad to fish with FADs? What are the real impacts of the use of drifting FADs on pelagic marine ecosystems? , 2013 .

[26]  Emmanuel Chassot,et al.  Statistics of the European Union and associated flags purse seine fishing fleet targeting tropical tunas in the Indian Ocean 1981-2013 , 2014 .

[27]  Javier Ariz,et al.  Effects of time-area closure on tropical tuna purse-seine fleet dynamics through some fishery indicators , 2011 .

[28]  Jon Lopez,et al.  Evolution and current state of the technology of echo-sounder buoys used by Spanish tropical tuna purse seiners in the Atlantic, Indian and Pacific Oceans , 2014 .

[29]  Javier Ariz,et al.  Spanish Fish Aggregating Device Management Plan. Preliminary data in the Indian Ocean. , 2014 .

[30]  Emmanuel Chassot,et al.  Bycatch of the European purse seine tuna fishery in the Atlantic Ocean for the 2003-2007 period , 2010 .

[31]  Frédéric Ménard,et al.  Drifting FADs used in tuna fisheries: an ecological trap? , 2000 .

[32]  F. Ménard,et al.  Food consumption of tuna in the Equatorial Atlantic ocean: FAD-associated versus unassociated schools , 2000 .

[33]  Emmanuel Chassot,et al.  The use of artificial fish aggregating devices by the French tropical tuna purse seine fleet: Historical perspective and current practice in the Indian Ocean , 2014 .

[34]  N. Dulvy,et al.  Global population trajectories of tunas and their relatives , 2011, Proceedings of the National Academy of Sciences.

[35]  H. Chang,et al.  Reproductive biology of female bigeye tuna Thunnus obesus in the western Pacific Ocean. , 2013, Journal of fish biology.

[36]  Frédéric Ménard,et al.  Do drifting and anchored Fish Aggregating Devices (FADs) similarly influence tuna feeding habits? A case study from the western Indian Ocean , 2011 .

[37]  Shelton J. Harley,et al.  The potential use of time-area closures to reduce catches of bigeye tuna (Thunnus obesus) in the purse-seine fishery of the eastern Pacific Ocean , 2007 .

[38]  L. Dagorn,et al.  How much do fish aggregating devices (FADs) modify the floating object environment in the ocean , 2013 .