Best standards for data collection and reporting requirements on FOBs: towards a science-based FOB fishery management.

A major concern for tropical tunas, on these last years, has been the worldwide increasing use of drifting FOBs by purse seiners, which are equipped with satellite buoys and echo-sounders. The use of these floating objects has contributed to increase the catch of skipjack tuna, but also of juveniles of yellowfin and bigeye tunas. Moreover, it has increased the amount of by-catch (including some species classified as vulnerable or endangered) and has likely resulted in adverse effects on the ecology of fish and on vulnerable areas (e.g. beaching events on coral reef areas). Despite the increasing FOB use and concerns, little information is available on FOB use worldwide for an appropriate monitoring and management. Thus, FOB monitoring has become a priority in all tuna t-RFMOs. However, the data collection and reporting requirements around FOBs are not standardized and there are significant data gaps. The aim of this document is to review current requirements and procedures in place and propose standards for data collection and submission on FOBs to tRFMOs. The proposals included in this document are the result of a collaborative work between scientists and the fishing industry

Derivation of consistent hard rock (1000<Vs<3000 m/s) GMPEs from surface and down-hole recordings: Analysis of KiK-net data

A key component in seismic hazard assessment is the estimation of ground motion for hard rock sites, either for applications to installations built on this site category, or as an input motion for site response computation. Empirical ground motion prediction equations (GMPEs) are the traditional basis for estimating ground motion while VS30 is the basis to account for site conditions. As current GMPEs are poorly constrained for VS30 larger than 1000 m/s, the presently used approach for estimating hazard on hard rock sites consists of “host-to-target” adjustment techniques based on VS30 and κ0 values. The present study investigates alternative methods on the basis of a KiK-net dataset corresponding to stiff and rocky sites with 500 < VS30 < 1350 m/s. The existence of sensor pairs (one at the surface and one in depth) and the availability of P- and S-wave velocity profiles allow deriving two “virtual” datasets associated to outcropping hard rock sites with VS in the range [1000, 3000] m/s with two independent corrections: 1/down-hole recordings modified from within motion to outcropping motion with a depth correction factor, 2/surface recordings deconvolved from their specific site response derived through 1D simulation. GMPEs with simple functional forms are then developed, including a VS30 site term. They lead to consistent and robust hard-rock motion estimates, which prove to be significantly lower than host-to-target adjustment predictions. The difference can reach a factor up to 3–4 beyond 5 Hz for very hard-rock, but decreases for decreasing frequency until vanishing below 2 Hz

Effects of the ICCAT FAD moratorium on the tuna fisheries and tuna stocks

International audienceCe document analyse le moratoire de l'ICCAT sur les DCP mis en oeuvre depuis 2013. L'analyse des prises réalisées sous DPC entre 2006 et 2012 a montré que 8,7 % et 5,3 % des captures sous DCP de thon obèse et d'albacore, respectivement, ont été réalisées dans les strates du moratoire. Pour ces dernières années (2013-2014), deux grandes flottilles ont opéré dans la zone : les flottilles de senneurs européens et associés et les navires ghanéens. Les deux flottilles ont bien respecté le moratoire au cours de ces années. La mise en oeuvre du moratoire a entraîné en janvier et février une diminution significative des captures sous DCP de la flottille ghanéenne, mais pas de la flottille européenne, étant donné que, pendant le moratoire, cette flottille pêchait efficacement sous DCP dans d'autres zones de pêche. Il n'y a pas eu de capture plus élevée dans la zone du moratoire en mars 2013-2014 et aucun changement visible dans la pêche en bancs libres. Les prises totales sous DCP ont été élevées au cours de la période 2011-2014. Ce moratoire a eu très peu d'impact en matière de protection des thons juvéniles ; il n'y a aucune preuve que ce règlement puisse améliorer considérablement l'état des stocks. Il conviendrait d'envisager une gestion alternative plus efficace de la pêche sous DCP, des fermetures de zones plus grandes et des mesures visant à réduire la surcapacité actuelle de la pêche sous DCP. RESUMEN Este documento analiza la moratoria de ICCAT a los DCP implementada desde 2013. El análisis de las capturas sobre DCP en 2006-2012 demostró que un 8,7% y un 5,3% de las capturas sobre DCP de patudo y rabil, respectivamente, fueron realizadas en los estratos de la moratoria. Para los años recientes (2013-2014), dos flotas principales han estado operando en la zona: los cerqueros europeos y asociados y los buques ghaneses. Ambas flotas han cumplido bien la moratoria durante estos años. La implementación de la moratoria ha producido un descenso significativo en las capturas de DCP durante enero-febrero para la flota ghanesa, pero no para la flota europea ya que durante la moratoria dicha flota ha pescado de forma eficaz sobre DCP en caladeros alternativos. No se produjeron capturas mayores en la zona de la moratoria en marzo de 2013-2014 y no se produjo ningún cambio visible en la pesca sobre bancos libres. Las capturas totales sobre DCP han sido elevadas durante el periodo 2011-2014. Esta moratoria ha tenido muy poco impacto en la protección de los túnidos juvenilesThis paper analyzes the ICCAT FAD moratorium implemented since 2013. Analysis of FAD catches in 2006-2012 showed that 8.7% and 5.3% of bigeye and yellowfin FAD catches respectively were caught in the moratorium strata. For recent years (2013-2014), two major fleets have been operating in the area: the European and associated purse seiners, and Ghanaian vessels. Both fleets have been well following the moratorium during these years. The moratorium implementation has produced a significant decrease in FAD catches during January February for the Ghanaian fleet, but not for the European fleet, as during the moratorium, this fleet was efficiently fishing on FADs in alternate fishing grounds. There was no higher catches in the moratorium area in March 2013-2014 and no visible change in the free school fishing. Total FAD catches have been high during the 2011-2014 period. This moratorium had very little impact in the protection of juvenile tuna; there is no evidence that this regulation may significantly improve stock status. More efficient alternate management of the FAD fishing should be envisaged, larger closed areas and measures targeting to reduce the today overcapacity of the FAD fishery

Preferred habitat of tropical tuna species in the Eastern Atlantic and Western Indian Oceans: a comparative analysis between FAD-associated and free-swimming schools

Abstract An ecological niche modelling (ENM) approach was developed to describe the suitable habitat of skipjack (SKJ) and juvenile yellowfin (YFT) tuna in the Tropical Atlantic and West Indian Oceans. The environmental envelop of the potential habitat in each ocean was defined using occurrence data independently of the fishing mode and derived from purse seine fishing sets of the French fleet during 1997-2014. Daily satellite-derived chlorophyll-a content (CHL) and fronts (CHL gradient) were used as a proxy for food availability while circulation model derived-sea surface temperature, salinity, height anomaly, current and oxygen as well as the mixed layer depth contributed to identify the physical suitable conditions of each species. Only the cluster that showed no CHL front was excluded for the parameterization in order to enhance the favourable feeding habitat. In a second step, the distances of both the free swimming schools (FSC) and schools associated with drifting Fishing Aggregating Devices (FADs) to the closest potential habitat were computed and compared. The results highlighted (i) high spatial seasonality of both the simulated feeding habitat and tuna populations in the Indian Ocean compared to the tropical Atlantic, (ii) major differences between both oceans regarding the distance of FAD catches to the potential habitat with median values above 200 km in the Atlantic and below 16 km in the Indian Ocean, while equivalent distances for FSC were observed for both species and areas (below 2 km and 43 km respectively) in agreement with stomach content analysis, (iii) an increased rate of FAD fishing operations in the decade from 2003 to 2013 (up to about 70% in the Atlantic and 96% in the Indian Ocean) occurring mostly in poor environments in the tropical Atlantic while frequently in relatively productive waters in the Indian Ocean (except east of 58°N) as well as an overall 300% increase of juvenile YFT presence in both ocean sets and (iv) a recent intensification of fishing effort from March to May in the Mozambique Channel in agreement with an increase of favourable habitat, while no effort of that fleet occurred in the open waters off the Gabon upwelling (from 1°N to 5°S and East of 17°W) from May to September where favourable habitat was enhanced by the model. In all cases the seasonal maximum number of fishing sets corresponded to the minimum extent of potential habitat, which commonly varied by 30% from year to year. Overall, this comparative analysis emphasizes the strong attraction of tropical tuna species to floating objects although feeding opportunities may vary considerably depending on hydrographic regimes and on the dynamics of productive habitats

Fishing on floating objects (FOBs) : how French tropical tuna purse seiners split fishing effort between GPS-monitored and unmonitored FOBs

Fishing on floating objects (FOBs) dominates catch in tropical tuna purse seine fisheries. One frequently cited advantage of deploying GPS-monitored FOBs is that the position information can be used for directed fishing to reduce search time for tuna. However, purse seiners also fish on foreign objects for which position information is not available. It is critical to quantify the prevalence of fishing on GPS-monitored versus unmonitored FOBs to understand how they impact fishing effort and catch per unit effort. We analyzed French commercial, observer, and FOB trajectory data in the Atlantic and Indian oceans to determine how often purse seine vessels fish on GPS-monitored FOBs. Only 2.7%-20.4% of French FOB fishing sets over 2007-2013 in both oceans were made on GPS-monitored FOBs. Though increasing over time, the low percentage suggests that French vessels do not primarily use GPS-monitored FOBs to reduce search time for tuna. We hypothesize that fishery-wide FOB deployments have important collective consequences for overall fishing effort and recommend that future effort metrics should be based on fishery-wide FOB activities

16ème groupe de travail sur les thons tropicaux

Recent resolutions of the Indian Ocean Tuna Commission (IOTC) have been implemented to improve scientific knowledge on the effects of drifting fish aggregating devices (DFADs) through increased data collection and reporting. Here, we report information on DFADs collected from three distinct data sources to describe the use of DFADs and buoys by the French PS fleet of the Indian Ocean over the last decade. First, archives of buoy purchase orders during 2002-2014 were provided by fishing companies to give insight into the historical use of DFADs. Data show an homogeneity of the numbers of buoys available to each purse seiner and a steady increase of about 10 buoys per year per vessel, from 50-60 in the early 2000s to 200 in 2013. Second, information derived from satellite transmission data was made available for the period 2010-2013 based on quarterly reports that are produced by buoy supplier companies on a vessel basis. Data show an overall relative stability of the number of French buoys having been used to monitor floating objects (FOBs) during 2010-2013. Each French purse seiner operating in the IO has been monitoring a mean number of 90 FOBs (predominated by DFADs) on a quarterly basis during 2010- 2013, with some variability between vessels and seasons. The total number of FOBs monitored for the French component of the European PS fleet would be around 1,200 in the recent years. Third, an extended version of the PS logbooks has been implemented since January 2013 to include information on DFADs and associated buoys. Although incomplete for some vessels, data collection has been improving over time and several skippers now report a large amount of information on DFADs on an operation basis. This information appears complementary to the two other sources of aggregated data and allows identifying the areas of DFAD deployments for instance

16ème groupe de travail sur les thons tropicaux

Since the mid 1990s, drifting Fish Aggregating Devices (dFADS), artificial objects specifically designed to aggregate fish, have become an important mean of catching tropical tunas in the Indian Ocean for the purse seine fleet. In recent years, the massive deployments of dFADs as well as the massive use of tracking GPS and echosounder buoys on dFADs and natural floating objects (logs) have raised serious concerns for tropical tuna stocks but also regarding the possible modifications in ecosystem functioning. However, relatively little remains known on the modalities of dFAD and tracking buoy use by purse seiners. These knowledge gaps render difficult the evaluation of the impacts of fishing practices with dFADs and logs. For the first time, the three French fishing companies operating or having operated in the Indian Ocean provided the GPS buoy tracks of a large proportion of the dFADs and logs monitored by the French fleet. Here, we combine this new source of information with observations of dFADs and logs by observers aboard French and Spanish purse seiners, quarterly French fishing companies orders of buoys, and interviews with purse seine skippers conducted in the port of Victoria. This allows us to identify 4 dFAD and log seasons, to understand the strategies of fishers regarding dFAD and tracking GPS buoy deployment, to extrapolate the total number of dFADs and GPS buoys used by all purse seine fleets and to examine some of the impacts of dFAD use in the Indian Ocean. The results we obtain are a first step for a better assessment and management of the purse seine dFAD fishery

Collecting information on the pelagic phase of marine turtles from at-sea observations: The case of purse seine fisheries in the Indian Ocean

Observations of turtles in the open-ocean are essential to complement the information collected at nesting sites and rookeries, especially during the ‘lost years’ of their surface-pelagic juvenile phase. We used a large dataset of observations at sea collected onboard Seychelles, Spanish and French purse seiners over the period 2003-2019 to describe the occurrence of five species of turtles in the Western Indian Ocean: green ( Chelonia mydas ), loggerhead ( Caretta caretta ), leatherback ( Dermochelys coriacea ), Olive ridley ( Lepidochelys olivacea ) and hawksbill ( Eretmochelys imbricata ). A total of 895 turtles were recorded by human observers, 487 turtles after having been caught in the purse seine and hauled onboard the vessels and 408 turtles swimming around or lying on floating objects. An additional 86 turtles were recorded from images collected by cameras deployed on some purse seiners but could not be identified at the species level. Information collected on the status of turtles indicates that the very large majority (>90%) hauled on deck were released alive. Size data show that most turtles observed in the open ocean were juveniles and that the ones caught in association with free swimming schools of tuna were smaller than the ones caught in schools associated with drifting floating objects, these latter representing the majority of the observations. Through the turtles’ example, we aim to describe the availability of metadata and data standards widely used to share species occurrence data and key to foster collaborative science in the Indian Ocean and beyond