Spatiotemporal distribution of fish schools around drifting fish aggregating devices

Omnidirectional sonar surveys were conducted in close proximity to drifting fish aggregating devices (FADs) offshore Seychelles, western Indian Ocean, to investigate the number, size, and distribution of FAD-associated fish schools. Echotrace detection techniques applied on the raw multibeam data enabled the extraction of empirical statistics regarding inter-school distances, and allowed the visualization of the temporal evolution of the pelagic aggregation on a FAD-centered coordinate system. The sonar recordings revealed the concurrent existence of multiple fish schools that were spatially clustered and exhibited low permanence in size and structure. Schools were predominantly detected within a radius of 500 m from the FADs, although 15% of detections occurred between 500 to 1500 m from the floating devices. Fish school biomass detected with the sonar was aggregated into a few, large schools during daytime, and dispersed into a larger number of small schools during nighttime. Compared to daytime observations, nighttime schools maintained smaller inter-school distances and were located closer to the drifting FADs. The study demonstrates that horizontal sonars are powerful tools for studying the spatiotemproral distribution of large pelagic schools in the vicinity of drifting FADs.

[1]  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 .

[2]  B. Partridge,et al.  The structure of schools of giant bluefin tuna in Cape Cod Bay , 1983, Environmental Biology of Fishes.

[3]  Tim Dempster,et al.  Fish aggregation device (FAD) research: gaps in current knowledge and future directions for ecological studies , 2004, Reviews in Fish Biology and Fisheries.

[4]  Thomas C. Weber,et al.  On the use of omnidirectional sonars and downwards-looking echosounders to assess pelagic fish distributions during and after midwater trawling , 2013 .

[5]  Christophe Collet,et al.  Omnidirectional multibeam sonar monitoring: applications in fisheries science , 2006 .

[6]  Jean-Louis Deneubourg,et al.  Impact of increasing deployment of artificial floating objects on the spatial distribution of social fish species , 2013 .

[7]  A. Fonteneau,et al.  ANALYSIS OF PURSE SEINE SET TIMES FOR FAD AND FREE SCHOOL ASSOCIATIONS IN THE ATLANTIC AND INDIAN OCEANS , 2010 .

[8]  Ole Arve Misund,et al.  Tracking herring schools with a high resolution sonar. Variations in horizontal area and relative echo intensity , 1998 .

[9]  D. Gaertner,et al.  Approximate estimate of the maximum sustainable yield from catch data without detailed effort information: application to tuna fisheries , 2001 .

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

[11]  Laurent Berger,et al.  The new fisheries multibeam echosounder ME70: description and expected contribution to fisheries research , 2008 .

[12]  Pierre Fréon,et al.  Dynamics of pelagic fish distribution and behaviour : effects on fisheries and stock assessment , 1999 .

[13]  R. Hilborn,et al.  ALTERNATIVE FISHERIES AND THE PREDATION RATE OF YELLOWFIN TUNA IN THE EASTERN PACIFIC OCEAN , 2002 .

[14]  Pierre Fréon,et al.  Review of fish associative behaviour: Toward a generalisation of the meeting point hypothesis , 2000, Reviews in Fish Biology and Fisheries.

[15]  E. John Simmonds,et al.  An operational system for automatic school identification on multibeam sonar echoes , 2009 .

[16]  J. Deneubourg,et al.  Does social behavior influence the dynamics of aggregations formed by tropical tunas around floating objects ? An experimental approach , 2013 .

[17]  George R. Cutter,et al.  Accounting for scattering directivity and fish behaviour in multibeam-echosounder surveys , 2007 .

[18]  May T. Lim,et al.  Modelling the impacts of fish aggregating devices (FADs) and fish enhancing devices (FEDs) and their implications for managing small-scale fishery , 2014 .

[19]  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 .

[20]  P. Petitgas,et al.  The influence of the environment on the variability of monthly tuna biomass around a moored, fish-aggregating device , 2009 .

[21]  Masahiko Furusawa,et al.  The average three-dimensional target strength of fish by spheroid model for sonar surveys , 2009 .

[22]  E. Romanov.  Bycatch in the tuna purse-seine fisheries of the western Indian Ocean , 2002 .

[23]  Ole Arve Misund,et al.  Underwater acoustics in marine fisheries and fisheries research , 1997, Reviews in Fish Biology and Fisheries.

[24]  Daniel W. Fuller,et al.  Simultaneous behavior of skipjack (Katsuwonus pelamis), bigeye (Thunnus obsesus), and yellowfin (T. albacares) tunas, within large multi-species aggregations associated with drifting fish aggregating devices (FADs) in the equatorial eastern Pacific Ocean , 2013 .

[25]  Daniel W. Fuller,et al.  Movements, behavior, and habitat selection of bigeye tuna (Thunnus obesus) in the eastern equatorial Pacific, ascertained through archival tags , 2002 .

[26]  Vasilis Trygonis,et al.  Adaptation of fisheries sonar for monitoring schools of large pelagic fish: dependence of schooling behaviour on fish finding efficiency , 2007 .

[27]  D. Gaertner,et al.  Drifting fish aggregation devices could act as an ecological trap for tropical tuna species , 2008 .

[28]  M. Potier,et al.  Interaction between fish and fishing vessels in the Javanese purse seine fishery , 1997 .

[29]  David Itano,et al.  Characterizing fish communities associated with drifting fish aggregating devices (FADs) in the Western Indian Ocean using underwater visual surveys , 2007 .

[30]  Daniel W. Fuller,et al.  Behavior of bigeye (Thunnus obesus) and skipjack (Katsuwonus pelamis) tunas within aggregations associated with floating objects in the equatorial eastern Pacific , 2005 .

[31]  E. John Simmonds,et al.  Fisheries Acoustics: Theory and Practice , 2005 .

[32]  Patrice Brehmer,et al.  Echotrace classification and spatial distribution of pelagic fish aggregations around drifting fish aggregating devices (DFAD) , 2007 .

[33]  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 .

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

[35]  Takayuki Matsumoto,et al.  Behavior of skipjack tuna (Katsuwonus pelamis) associated with a drifting FAD monitored with ultrasonic transmitters in the equatorial central Pacific Ocean , 2014 .

[36]  T. Pitcher,et al.  When fish shoals meet: outcomes for evolution and fisheries , 2003 .

[37]  David Itano,et al.  Satellite-linked acoustic receivers to observe behavior of fish in remote areas , 2007 .

[38]  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 .

[39]  J. Castro,et al.  A general theory on fish aggregation to floating objects: An alternative to the meeting point hypothesis , 2002, Reviews in Fish Biology and Fisheries.

[40]  J. Deneubourg,et al.  The aggregation of tuna around floating objects: what could be the underlying social mechanisms? , 2014, Journal of theoretical biology.

[41]  Philippe Gaspar,et al.  Fishing activity of tuna purse seiners estimated from vessel monitoring system (VMS) data , 2011 .

[42]  Noël Diner,et al.  Correction on school geometry and density: approach based on acoustic image simulation , 2001 .

[43]  L. Dagorn,et al.  Visual censuses around drifting fish aggregating devices (FADs): a new approach for assessing the diversity of fish in open-ocean waters , 2008 .

[44]  D. Gaertner,et al.  Exploitation of small tunas by a purse-seine fishery with fish aggregating devices and their feeding ecology in an eastern tropical Atlantic ecosystem , 2000 .

[45]  Daniel Gaertner,et al.  Influence of fishers’ behaviour on the catchability of surface tuna schools in the Venezuelan purse-seiner fishery in the Caribbean Sea , 1999 .

[46]  L. Dagorn,et al.  Modeling tuna behaviour near floating objects: from individuals to aggregations , 2000 .

[47]  Nathaniel K. Newlands,et al.  Measurement of the size, shape and structure of Atlantic bluefin tuna schools in the open ocean , 2008 .

[48]  Mathieu Doray,et al.  Acoustic characterisation of pelagic fish aggregations around moored fish aggregating devices in Martinique (Lesser Antilles) , 2006 .

[49]  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 .

[50]  Erwan Josse,et al.  Typology and behaviour of tuna aggregations around fish aggregating devices from acoustic surveys in French Polynesia , 2000 .

[51]  C. Mullon,et al.  Diurnal variation in fish density estimate during acoustic surveys in relation to spatial distribution and avoidance reaction , 1993 .