Tracking Buoys Research Articles

First look at the distribution of deactivated dFADs used by the French Indian Ocean tropical tuna purse-seine fishery

Abstract The presence of abandoned, lost or otherwise discarded fishing gears, including drifting fish aggregating devices (dFADs), in marine ecosystems poses significant ecological and socioeconomic concerns. The estimation of the number of dFADs in the marine environment is challenging due to the loss of tracking information when dFAD tracking buoys are remotely deactivated. For the first time, a data set of dFADs buoy positions, including those that had previously been remotely deactivated, has been made available for the period July–August 2020. Data from this period provide valuable insights into the life expectancy, spatial distribution, and status of deactivated dFAD buoys, enabling a more accurate assessment of dFAD presence and impacts. Deactivated buoys represented a 17.2% increase in the total number of tracked objects, and we estimate the in-water half-life of deactivated dFAD tracking buoys to be 101 days. Including deactivated buoys increases the number of strandings during the SP by 23.7%. Nevertheless, the representativity of these results is unknown given the limited spatio-temporal and numerical extent of our data, highlighting the importance of availability of comprehensive data on dFADs to effectively estimate their total numbers and mitigate their environmental impacts.

Direct Observations of Wave‐Sea Ice Interactions in the Antarctic Marginal Ice Zone

AbstractWave energy propagating into the Antarctic marginal ice zone effects the quality and extent of the sea ice, and wave propagation is therefore an important factor for understanding and predicting changes in sea ice cover. Wave‐sea ice interactions are notoriously hard to model and in situ observations of wave activity in the Antarctic marginal ice zone are scarce, due to the extreme conditions of the region. Here, we provide new in situ data from two drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys deployed in the Weddell Sea in the austral winter and spring of 2019. The buoy location ranges from open water to more than 200 km into the sea ice. We estimate the attenuation of swell with wave periods 8–18 s, and find an attenuation coefficient α = 4 · 10−6 to 7 · 10−5 m−1 in spring, and approximately five‐fold larger in winter. The attenuation coefficients show a power law frequency dependence, with power coefficient close to literature. The in situ data also shows a change in wave direction, where wave direction tends to be more perpendicular to the ice edge in sea ice compared to open water. A possible explanation for this might be a change in the dispersion relation caused by sea ice. These observations can help shed further light on the influence of sea ice on waves propagating into marginal ice zones, aiding development of coupled wave‐sea ice models.

Positioning of Unmanned Underwater Vehicle Based on Autonomous Tracking Buoy.

This paper presents a novel method for the dynamic positioning of an unmanned underwater vehicle (UUV) with unknown trajectories based on an autonomous tracking buoy (PUVV-ATB) that indirectly positions the UUV using ultra-short baseline measurements. The method employs a spatial location geometric model and divides the positioning process into four steps, including data preprocessing to detect geometric errors and apply mean filtering, direction capture, position tracking, and position synchronization. To achieve these steps, a new adaptive tracking control algorithm is proposed that does not require trajectory prediction and is applied to the last three steps. The algorithm is deployed to the buoy for tracking simulation and sea trial experiments, and the results are compared with those of a model predictive control algorithm. The autonomous tracking buoy based on the adaptive tracking control algorithm runs more stably and can better complete the precise tracking task for the UUV with a positioning error of less than 10 cm. This method breaks the premise of trajectory prediction based on traditional tracking control algorithms, providing a new direction for further research on UUV localization. Furthermore, the conclusion of this paper has important reference value for other research and application fields related to UUV.

Spatio-temporal variability in drifting Fish Aggregating Device (dFAD) beaching events in the Seychelles Archipelago

AbstractPurse-seine fisheries use drifting Fish Aggregating Devices (dFADs), human-made floating objects, to facilitate the capture of tropical tunas. Currently, the majority of dFADs are constructed primarily of highly durable non-biodegradable materials and there is no legal obligation to recover dFADs after deployment, leading to beaching events and potentially negative environmental impacts. We assessed beachings as a function of intra- and inter-annual trends, water depth, distance from land, seasonality, and benthic habitat within the local context of the Seychelles Archipelago using trajectories of dFADs deployed by French purse seiners over 2008–2020. Overall, 3842 beaching events associated with 2371 distinct dFAD tracking buoys were identified. Beachings occurred most frequently during the winter monsoon (December–March). Due to the shallow Mahé Plateau, beachings occurred in both nearshore (≤ 5 km from land) and offshore (> 5 km) regions, predominantly in estimated depths less than 60 m. Despite representing < 20% of overall mapped habitat, the benthic habitat “Coral/Algae” had the highest beaching rate (35.3% of beachings), and therefore, beachings pose a significant concern for conservation. Our results provide a detailed view of the spatio-temporal pattern of beachings in the Seychelles, supporting the development of mitigation and prevention methods to reduce marine debris and perturbations to the marine environment.

Recovery at sea of abandoned, lost or discarded drifting fish aggregating devices

Tropical tuna purse-seine fishing vessels contribute to abandoned, lost or discarded (ALD) fishing equipment by deploying large numbers of drifting Fish Aggregating Devices (dFADs). Here we analysed more than 80,000 dFAD trajectories (56,263 tracking buoys) in the Indian and Atlantic oceans from 2012 to 2018. We found that more than 40% of dFAD trajectories ultimately drifted away from fishing grounds, becoming ALD. About 20% of these lost dFADs passed within 50 km of major ports, indicating that port-based programmes could be effective in collecting ALD dFADs at sea. We also identified areas within the fishing grounds where most dFADs exit and where high-seas recovery could be valuable. For example, most dFADs leaving Indian Ocean fishing grounds along their eastern border at ~70° E, particularly in October–December, do not return to fishing grounds. Despite considerable logistical challenges, at-sea dFAD recovery offers promising options for reducing the ecological footprints of purse-seine fisheries. Nearly half of drifting fish aggregating devices in the Indian and Atlantic oceans becomes abandoned, lost or discarded. However, a substantial portion of this pollution passes near major ports, hence port-based recovery presents a promising strategy to reduce fishing-related marine pollution.

Surface habitat modification through industrial tuna fishery practices

Abstract Natural floating objects (FOBs) have always been a major component of the habitat of pelagic species. Since the 1990s, the number of FOBs in the open ocean has increased greatly as a result of the introduction of fish aggregating devices (FADs) by the industrial tropical tuna purse seine vessels. These changes, and their potential impacts on the species that associate with FOBs, remain poorly understood. Using fisheries observer data, data from satellite-linked tracking buoys attached to FOBs and Lagrangian simulations, this study quantifies the temporal changes in the density and spatial distribution of FOBs due to the use of FADs in the Indian Ocean (IO) between 2006 and 2018. From 2012 to 2018, the entire western IO is impacted, with FADs representing more than 85% of the overall FOBs, natural FOBs less than 10%, and objects originating from pollution 5%. Results also suggest that both FADs and natural FOBs densities are lower in the eastern IO, but this initial investigation highlights the need for further studies. Our study confirms that FADs have greatly modified the density and spatial distribution of FOBs, which highlights the need to investigate potential consequences on the ecology of associated species.

Rapid deterministic wave prediction using a sparse array of buoys

A long-standing problem in maritime operations and ocean development projects has been the prediction of instantaneous wave energy. Wave measurements collected using an array of freely drifting arrays of Surface Wave Instrument Float with Tracking (SWIFT) buoys are used to test methods for phase-resolved wave prediction in a wide range of observed sea states. Using a linear inverse model in directionally-rich, broadbanded wave fields can improve instantaneous heave predictions by an average of 63% relative to statistical forecasts based on wave spectra. Numerical simulations of a Gaussian sea, seeded with synthetic buoys, were used to supplement observations and characterize the spatiotemporal extent of reconstruction accuracy. Observations and numerical results agree well with theoretical deterministic prediction zones proposed in previous studies and suggest that the phase-resolved forecast horizon is between 1–3 average wave periods for a maximum measurement interval of 10 wave periods for ocean wave fields observed during the experiment. Prediction accuracy is dependent on the geometry and duration of the measurements and is discussed in the context of the nonlinearity and bandwidth of incident wave fields.

A surface kinematics buoy (SKIB) for wave–current interaction studies

Abstract. Global navigation satellite systems (GNSSs) and modern motion-sensor packages allow the measurement of ocean surface waves with low-cost drifters. Drifting along or across current gradients provides unique measurements of wave–current interactions. In this study, we investigate the response of several combinations of GNSS receiver, motion-sensor package and hull design in order to define a prototype “surface kinematics buoy” (SKIB) that is particularly optimized for measuring wave–current interactions, including relatively short wave components that are important for air–sea interactions and remote-sensing applications. The comparison with existing Datawell Directional Waverider and Surface Wave Instrument Float with Tracking (SWIFT) buoys, as well as stereo-video imagery, demonstrates the performance of SKIB. The use of low-cost accelerometers and a spherical ribbed and skirted hull design provides acceptable heave spectra E(f) from 0.09 to 1 Hz with an acceleration noise level (2πf)4E(f) close to 0.023 m2 s−3. Velocity estimates from GNSS receivers yield a mean direction and directional spread. Using a low-power acquisition board allows autonomous deployments over several months with data transmitted by satellite. The capability to measure current-induced wave variations is illustrated with data acquired in a macro-tidal coastal environment.

Turbulence from Breaking Surface Waves at a River Mouth

AbstractObservations of surface waves, currents, and turbulence at the Columbia River mouth are used to investigate the source and vertical structure of turbulence in the surface boundary layer. Turbulent velocity data collected on board freely drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys are corrected for platform motions to estimate turbulent kinetic energy (TKE) and TKE dissipation rates. Both of these quantities are correlated with wave steepness, which has previously been shown to determine wave breaking within the same dataset. Estimates of the turbulent length scale increase linearly with distance from the free surface, and roughness lengths estimated from velocity statistics scale with significant wave height. The vertical decay of turbulence is consistent with a balance between vertical diffusion and dissipation. Below a critical depth, a power-law scaling commonly applied in the literature works well to fit the data. Above this depth, an exponential scaling fits the data well. These results, which are in a surface-following reference frame, are reconciled with results from the literature in a fixed reference frame. A mapping between free-surface and mean-surface reference coordinates suggests 30% of the TKE is dissipated above the mean sea surface.

Relative influences of the metocean forcings on the drifting ice pack and estimation of internal ice stress gradients in the Labrador Sea

AbstractUnderstanding the relative influences of the metocean forcings on the drift of sea ice floes is a crucial component to the overall characterization of an ice environment and to developing an understanding of the factors controlling the ice dynamics. In addition, estimating the magnitude of the internal stress gradients on drifting sea ice floes generated by surrounding ice cover is important for modeling operations, informing the design of offshore structures and vessels in ice environments, and for the proper calibration of Discrete Element Models (DEM) of fields of drifting ice floes. In the spring of 2015 and 2016, four sea ice floes offshore Makkovik, Labrador were tagged with satellite‐linked ice tracking buoys along with one satellite‐linked weather station on each floe to transmit wind speed and direction. Twenty satellite‐linked Lagrangian surface ocean current tracking buoys were also deployed in the open water adjacent to the targeted ice floes. In this paper, the dynamics of the four ice floes are explored in terms of the relative proportions which were forced by the wind, current, sea surface topography, Coriolis, and internal stress gradients. The internal ice stress gradients are calculated as residuals between the observed accelerations of the floes as measured by the tracking buoys and the sums of the other metocean forcings. Results show that internal ice stress gradients accounted for up to 50% of the observed forcing on the floes, and may have reached up to around 0.19 kPa.

Oil spill tracking buoy—revolutionising offshore response and recovery

April 2014 marked the four-year anniversary of the BP Deepwater Horizon Disaster; a rig explosion in the Gulf of Mexico that killed 11 workers and led to the worst offshore oil spill in US history. Oil gushed from the sea floor for 87 days before the well was capped an estimated 5 million BBL spilled into the Gulf, inflicting untold environmental damage. The event highlighted how little the industry knows about containing deep-water oil spills or about how oil spreads. Oil washed up hundreds of miles away on coastlines in Louisiana, Alabama, Mississippi and Florida, but scientists struggled to determine where all of the oil had gone. Had some of it evaporated or was it hiding below the surface? Had it been carried by currents to the Gulf’s deep waters or perhaps even further? No one can say for sure. The resulting science highlighted that oil drifts along the surface of ocean water at 97% of current speed, but at only a fraction of the wind speed. During the Deepwater Horizon Disaster, the tracking buoys sat too proud and were driven the wrong way by the wind. It is essential to track the currents, since they account for at least 95%–98% of the ultimate oil spill trajectory. WorleyParsons designed, developed and deployed an oil spill tracking buoy (OSTB) to provide a scientific instrument for capturing only the surface currents. The specific gravity of each buoy is such that it tracks surface currents. Material selection and manufacture, ocean validation and telecommunication engineers came together to produce such a device, which is largely underwater but can continue to communicate with satellites.

Analysis of floating debris behaviour in the Nakdong River basin of the southern Korean peninsula using satellite location tracking buoys

Most land-based debris enters the ocean via rivers during the rainy season. The Nakdong River system, the largest river entering the South Sea of Korea, discharges 3000tons of debris per year. We deployed small tracking buoys with satellite location transmitters to monitor river-borne floating debris movement. The buoys moved for various distances depending on the change in flux in different regions. A hot spot was expected to contain a large accumulation of floating debris. The central and lower parts of the eastern downstream region were identified as important regions. The results of this study provide information related to the movement of debris that can be used when establishing a method for collection of floating debris from rivers and streams. The study contributes to efforts to decrease the amount of floating debris in oceans and the costs associated with debris removal by improving the effectiveness of preventative measures.

낙동강 유출 부유쓰레기의 거동 특성

낙동강은 하구의 수문 개방 시 연간 수천 톤의 쓰레기가 남해로 유입되어 인근 연안을 이동하며 사회 경제적 피해를 유발하고 있다. 이에 본 연구에서 낙동강 유출 부유쓰레기의 거동 특성을 파악하기 위해 2012년 장마, 태풍 내습 시를 대상으로 피해지로 추정되는 거제도 북동측 해안 1개소에 대한 조사와 부이를 활용한 이동 경로 추적 시험을 수행하였다. 또한, 해양기상 환경에 대한 분석을 통해 부유쓰레기의 이동과 관련된 흐름을 파악하였다. 연구 결과 장마 시기인 7월 16일 초목류를 비롯한 총 40톤 정도의 쓰레기가 흥남해수욕장으로 유입되었다. 또한 9월 14일 태풍 '산바' 내습 시기에 투하된 위치 추적 부이는 가덕도 남쪽 해상을 지나 1 ~ 2일 후 거제도 해안가로 유입되는 결과를 보여주었다. 부유쓰레기와 위치 추적 부이가 거제도 북동측 해안가로 유입될 당시 거제 해역에서 북동풍계열의 풍향이 지배적이었으며 연안으로 유입되는 공통적인 해수 표층 흐름이 나타났다. When the mouth of the Nakdong River, opens its floodgate, thousands of tons of litter should flown into the South Sea, moving towards nearby coast, thus causing serious social and economic damage. For this reason, in the present study, research was performed on one certain area in northeast coast of Geoje island, which is assumed as area damaged due to rainy season and typhoon in 2012, and research for trace of movement route was implemented by using buoy to identify characteristic of movement of floating debris caused from Nakdong River. Flows related to the movement of floating debris was also identified by analyzing ocean meteorological environment. As a result of the study, total 40 tons of litter composed of grasses and trees(or plants litter) were flown into Heungnam beach on 16th, Jul which is the rainy season. Plus, the location tracking buoy, which was dropped when the typhoon SANBA was coming, was passed by southern sea of Gadeok-do and was flown into Geoje beach 1 ~ 2 days after it was dropped. The wind direction was mostly northeasterly wind around the Geoje beach at the time the buoy and floating debris were flown into northeast coast and there was common sea surface currents which was flowing into the coast.

Research on Spilled Oil Alarming and Tracking Buoy System

The spilled oil alarming and tracking buoy system includes monitoring software and hardware, oil spillage sensor, and spilled oil alarming and tracking buoys. To buoy terminal directly after water, GPS positioning signal, and micro will be parsed real-time location information (position, speed, time, etc.) through wireless communication system (satellite networks or GSM network) to monitor the platform. Monitoring software can in electronic chart intuitive to display buoy, send the real-time controlled buoy updating, and change the transmission time interval.

Observation-based evaluation of surface wave effects on currents and trajectory forecasts

Knowledge of upper ocean currents is needed for trajectory forecasts and is essential for search and rescue operations and oil spill mitigation. This paper addresses effects of surface waves on ocean currents and drifter trajectories using in situ observations. The data set includes colocated measurements of directional wave spectra from a wave rider buoy, ocean currents measured by acoustic Doppler current profilers (ADCPs), as well as data from two types of tracking buoys that sample the currents at two different depths. The ADCP measures the Eulerian current at one point, as modelled by an ocean general circulation model, while the tracking buoys are advected by the Lagrangian current that includes the wave-induced Stokes drift. Based on our observations, we assess the importance of two different wave effects: (a) forcing of the ocean current by wave-induced surface fluxes and the Coriolis–Stokes force, and (b) advection of surface drifters by wave motion, that is the Stokes drift. Recent theoretical developments provide a framework for including these wave effects in ocean model systems. The order of magnitude of the Stokes drift is the same as the Eulerian current judging from the available data. The wave-induced momentum and turbulent kinetic energy fluxes are estimated and shown to be significant. Similarly, the wave-induced Coriolis–Stokes force is significant over time scales related to the inertial period. Surface drifter trajectories were analysed and could be reproduced using the observations of currents, waves and wind. Waves were found to have a significant contribution to the trajectories, and we conclude that adding wave effects in ocean model systems is likely to increase predictability of surface drifter trajectories. The relative importance of the Stokes drift was twice as large as the direct wind drag for the used surface drifter.

Comparison of Operational Oil Spill Trajectory Forecasts with Surface Drifter Trajectories in the Barents Sea

Six iSPHERE oil spill and current tracking buoys were deployed over the continental shelf of northern Norway (Nordkapp region) during spring-summer 2011. These drifters provide real-time GPS position location information to aid in locating marine oil spills and other leeward drifting objects. In this study we assess the differences between the spreading of the surface drifters and the trajectories forecast by the operational Lagrangian oil drift model at the Norwegian Meteorological Institute (met.no). The study investigates the reason for these differences, and we use a recently established new skill score as a measure of the model accuracy. The differences observed in this study are the consequence of the combined impact of the modeled wind, ocean and current constituents that force the oil drift model. Each numerical model is run on a grid of 4 km resolution, which means that many mesoscale features are either not represented well enough, or not represented at all. A problem with the ocean model, since eddies in the ocean are typically of a much smaller scale than in the atmosphere (40-50 km), and there are few observations to assimilate into the model. Studies such as this, comparing modeled trajectories with observed drifter trajectories are an important way to indirectly validate and improve ocean models, as well as improving the trajectory model itself.

Using local ecological knowledge (LEK) to provide insight on the tuna purse seine fleets of the Indian Ocean useful for management

The purse seine fishery in the Western Indian Ocean is dominated by Spanish and French vessels that rely heavily on the use of drifting fish aggregation devices (DFADs) to capture tropical tuna species (skipjack, yellowfin and bigeye tuna). This study uses local ecological knowledge (LEK) obtained through standardized interviews of fishing masters to compare and characterize the body of local ecological knowledge, fishing technology and fishing strategies of both fleets, with the goal of obtaining useful information for the management of the fishery. A notable difference between fleets was the number of DFADs actively monitored per vessel at any given time, which was much higher for Spanish vessels (ca. 60 versus 20 DFADs). Spanish vessels also achieved higher vessel CPUE (catch per DFAD set) than their French counterparts. The use of supply vessels to manage, monitor and protect productive DFADs, and the latest satellite-based technology to track and remotely monitor DFAD aggregations is restricted to the Spanish fleet. The French do not use supply vessels and deploy less sophisticated tracking buoys. These technological disparities resulted in some fishing strategy differences between both fleets, but few differences were found in the knowledge of tuna behavior accumulated by the fishers.

Use of Airborne Thermal Imagery to Detect and Monitor Inshore Oil Spill Residues During Darkness Hours.

/ Trials were conducted using an airborne video system operating in the visible, near-infrared, and thermal wavelengths to detect two known oil spill releases during darkness at a distance of 10 nautical miles from the shore in St. Vincent's Gulf, South Australia. The oil spills consisted of two 20-liter samples released at 2-h intervals, one sample consisted of paraffinic neutral material and the other of automotive diesel oil. A tracking buoy was sent overboard in conjunction with the release of sample 1, and its movement monitored by satellite relay. Both oil residues were overflown by a light aircraft equipped with thermal, visible, and infrared imagers at a period of approximately 1 h after the release of the second oil residue. Trajectories of the oil residue releases were also modeled and the results compared to those obtained by the airborne video and the tracking buoy. Airborne imagery in the thermal wavelengths successfully located and mapped both oil residue samples during nighttime conditions. Results from the trial suggest that the most advantageous technique would be the combined use of the tracking beacon to obtain an approximate location of the oil spill and the airborne imagery to ascertain its extent and characteristics.KEY WORDS: Airborne video; Thermal imagery; Global positioning; Oil-spill monitoring; Tracking beacon

COASTMAP: An integrated monitoring and modeling system to support oil spill response

One of the most difficult tasks in oil spill response modeling is to provide accurate estimates of the currents and winds during the spill event. This is typically done in an ad-hoc, subjective manner combining very limited field observations with simplified hydrodynamic and meteorological models. As an alternative an integrated environmental monitoring and modeling system, called COASTMAP, is presented. COASTMAP allows the user to collect, manipulate, display, and archive real-time environmental data through an embedded geographic information system and environmental data management tools; to perform simulations with a suite of environmental models (e.g. hydrodynamics, meteorological) in order to predict dynamics in the operational area and to assimilate real-time data into the models to allow hindcasting, nowcasting and forecasting. COASTMAP, operational on a personal computer, is controlled by mouse/keyboard through a series of menus and uses color graphics to present model predictions (plots, graphs, animations) and the results of data analyses. The software is designed using a shell based architecture making application to any geographic location simple and straightforward. In the present paper, COASTMAP is linked with OILMAP to provide a fully operational, real-time system that allows prediction of circulation, winds and oil spill trajectory and fate for estuarine and coastal sea areas. System performance is illustrated by the simulation of the trajectory of oil tracking buoys during two experiments performed in the lower west passage of Narragansett Bay. Simulation results using several forecast procedures, with/without real-time data, are presented.

The structure and propagation of a Gulf Stream frontal eddy along the North Carolina Shelf Break

The Frontal Eddy Dynamics (FRED) experiment, conducted offshore North Carolina between Cape Fear and Cape Hatteras, included a multiplatform intensive survey phase in May 1987. The intensive phase data set includes satellite infrared imagery, aircraft‐ and shipboard‐deployed expendable bathythermographs, moored current meters and thermistors, and satellite‐tracked drifting buoys. These observations are used to examine the structure and propagation of Eddy Abbott, the most extensively surveyed frontal eddy in this study. The analysis includes the use of a frontal eddy feature model to calculate the surface circulation and propagation characteristics of Eddy Abbott's cold dome from the buoy trajectories. The observations and analyses presented are unique in that Eddy Abbott is the first Gulf Stream frontal eddy seeded with tracking buoys to be followed beyond Cape Hatteras. Previously, frontal eddies were assumed to be sheared apart as they approached the confining topography of Cape Hatteras, leaving the near surface nutrient rich waters of the cold dome stranded on the North Carolina shelf. The in situ tracking data provided by the buoys indicate that rather than being stranded, Eddy Abbott's cold dome accelerates, propagating out of the South Atlantic Bight beyond Cape Hatteras.