scholarly journals Tracking Atlantic bluefin tuna from foraging grounds off the west coast of Ireland

2020 ◽  
Vol 77 (6) ◽  
pp. 2066-2077
Author(s):  
Thomas W Horton ◽  
Barbara A Block ◽  
Alan Drumm ◽  
Lucy A Hawkes ◽  
Macdara O’Cuaig ◽  
...  
Keyword(s):  
North Atlantic ◽  
West Coast ◽  
Time Series Data ◽  
Fork Length ◽  
Bluefin Tuna ◽  
Series Data ◽  
Future Research ◽  
The West ◽  
Northeast Atlantic ◽  
Atlantic Bluefin Tuna

Abstract Pop-up archival tags (n = 16) were deployed on Atlantic bluefin tuna (ABT) off the west coast of Ireland in October and November 2016 (199–246 cm curved fork length), yielding 2799 d of location data and 990 and 989 d of depth and temperature time-series data, respectively. Most daily locations (96%, n = 2651) occurred east of 45°W, the current stock management boundary for ABT. Key habitats occupied were the Bay of Biscay and the Central North Atlantic, with two migratory patterns evident: an east-west group and an eastern resident group. Five out of six tags that remained attached until July 2017 returned to the northeast Atlantic after having migrated as far as the Canary Islands, the Mediterranean Sea (MEDI) and the Central North Atlantic. Tracked bluefin tuna exhibited a diel depth-use pattern occupying shallower depths at night and deeper depths during the day. Four bluefin tuna visited known spawning grounds in the central and western MEDI, and one may have spawned, based on the recovered data showing oscillatory dives transecting the thermocline on 15 nights. These findings demonstrate the complexity of the aggregation of ABT off Ireland and, more broadly in the northeast Atlantic, highlighting the need for dedicated future research to conserve this important aggregation.

scholarly journals LSTM Networks to Improve the Prediction of Harmful Algal Blooms in the West Coast of Sabah

2021 ◽  
Vol 18 (14) ◽  
pp. 7650
Author(s):  
Fatin Nadiah Yussof ◽  
Normah Maan ◽  
Mohd Nadzri Md Reba
Keyword(s):  
West Coast ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Time Series Data ◽  
Short Term Memory ◽  
Harmful Algal Bloom ◽  
Series Data ◽  
Severe Illness ◽  
The West ◽  
Chl A

Harmful algal bloom (HAB) events have alarmed authorities of human health that have caused severe illness and fatalities, death of marine organisms, and massive fish killings. This work aimed to perform the long short-term memory (LSTM) method and convolution neural network (CNN) method to predict the HAB events in the West Coast of Sabah. The results showed that this method could be used to predict satellite time series data in which previous studies only used vector data. This paper also could identify and predict whether there is HAB occurrence in the region. A chlorophyll a concentration (Chl-a; mg/L) variable was used as an HAB indicator, where the data were obtained from MODIS and GEBCO bathymetry. The eight-day dataset interval was from January 2003 to December 2018. The results obtained showed that the LSTM model outperformed the CNN model in terms of accuracy using RMSE and the correlation coefficient r as the statistical criteria.

scholarly journals Otolith shape variation provides a marker of stock origin for north Atlantic bluefin tuna (Thunnus thynnus)

2016 ◽  
Vol 67 (7) ◽  
pp. 1023 ◽  
Author(s):  
Deirdre Brophy ◽  
Paula Haynes ◽  
Haritz Arrizabalaga ◽  
Igaratza Fraile ◽  
Jean Marc Fromentin ◽  
...  
Keyword(s):  
North Atlantic ◽  
Stock Assessment ◽  
Fork Length ◽  
Bluefin Tuna ◽  
Shape Variation ◽  
Thunnus Thynnus ◽  
Mixing Rate ◽  
Otolith Shape ◽  
Atlantic Bluefin Tuna ◽  
Significant Difference

Two stocks of bluefin tuna (Thunnus thynnus) inhabit the north Atlantic; the western and eastern stocks spawn in the Gulf of Mexico and the Mediterranean Sea respectively. Trans-Atlantic movements occur outside spawning time whereas natal homing maintains stock structure. Commercial fisheries may exploit a mixed assemblage of both stocks. The incorporation of mixing rates into stock assessment is precluded by uncertainties surrounding stock discrimination. Otolith shape descriptors were used to characterise western and eastern stocks of Atlantic bluefin tuna in the present study and to estimate stock composition in catches of unknown origin. Otolith shape varied with length and between locations and years. Within a restricted size range (200–297-cm fork length (FL)) the two stocks were distinguished with an accuracy of 83%. Bayesian stock mixture analysis indicated that samples from the east Atlantic and Mediterranean were predominantly of eastern origin. The proportion assigned to the eastern stock showed slight spatial variation; however, overlapping 95% credible intervals indicated no significant difference (200–297cm FL: central Atlantic, 73–100%; Straits of Gibraltar, 73–100%; Morocco, 50–99%; Portugal 64–100%). Otolith shape could be used in combination with other population markers to improve the accuracy of mixing rate estimates for Atlantic bluefin tuna.

Tracking the fidelity of Atlantic bluefin tuna released in Canadian waters to the Gulf of Mexico spawning grounds

2015 ◽  
Vol 72 (11) ◽  
pp. 1700-1717 ◽  
Author(s):  
Steven G. Wilson ◽  
Ian D. Jonsen ◽  
Robert J. Schallert ◽  
James E. Ganong ◽  
Michael R. Castleton ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Fork Length ◽  
Bluefin Tuna ◽  
Deepwater Horizon ◽  
Series Data ◽  
Spawning Grounds ◽  
Atlantic Bluefin Tuna ◽  
Drilling Rig ◽  
Archival Tags ◽  
The Mean

The objective of this study was to advance the use of pop-up satellite archival tags to track the migrations of Atlantic bluefin tuna (Thunnus thynnus) to their spawning grounds. Deployment of tags occurred in the Gulf of St. Lawrence, Canada, during fall months from 2007 to 2013. Pop-up satellite archival tags (n = 135) were attached to 125 Atlantic bluefin tuna (curved fork length (CFL) = 268 ± 20 cm (mean ± SD)) with the objective of keeping tags on until visitation to a spawning area or longer. A dataset of 18 800 days was acquired, which included 5800 days of time-series data from 19 recovered satellite tags. Many Atlantic bluefin tuna visited the Gulf of Mexico spawning grounds (74%), the mean size of which was 275 ± 14 cm (CFL ± SD, n = 49), with a measured CFL of 243 to 302 cm. These fish had a mean entry date into the Gulf of Mexico of 14 January ± 42 days (SD). The mean residency period for fish that had tracks with entrance and exit from the Gulf of Mexico was 123 ± 49 days (SD) (n = 22). Atlantic bluefin tuna that moved into the Gulf of Mexico during the spawning season remained west of the 45°W meridian for the duration of the track. Electronic tagging datasets from two fish were obtained before, during, and after the Deepwater Horizon oil spill. Both fish utilized habitat in the vicinity of the Macondo Well on 20 April 2010 when the Deepwater Horizon oil drilling rig accident occurred. Spawning hotspots are identified in the Gulf of Mexico using kernel density analyses and compared with the newly established closed areas.

scholarly journals Genetic heterogeneity of Atlantic bluefin tuna caught in the eastern North Atlantic Ocean south of Iceland

2006 ◽  
Vol 63 (6) ◽  
pp. 1111-1117 ◽  
Author(s):  
Jens Carlsson ◽  
Jan R. McDowell ◽  
Jeanette E.L. Carlsson ◽  
Droplaug Ólafsdóttir ◽  
John E. Graves
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Bluefin Tuna ◽  
Commercial Fishing ◽  
Northeast Atlantic ◽  
Atlantic Bluefin Tuna ◽  
Eastern North Atlantic ◽  
Abrupt Shifts ◽  
Mixed Stock ◽  
Significant Genetic Divergence

Abstract Atlantic bluefin tuna (Thunnus thynnus) are currently managed by the member nations of the International Commission for the Conservation of Atlantic Tunas (ICCAT) as distinct western and eastern stocks, separated by the 45°W meridian. Previous studies of Atlantic bluefin tuna caught in the northeast Atlantic south of Norway suggested mixing of putative stocks in the region, based on abrupt shifts in the size and condition of fish during the fishing season. By contrast, more recent studies south of Iceland reported only small differences in size of tuna caught at different times of the season in that area. To better understand the stock structure and composition of Atlantic bluefin tuna in the region, we surveyed genetic variation at eight microsatellite loci for 800 Atlantic bluefin tuna collected in experimental commercial fishing operations south of Iceland during 1999 and 2002. We tested for heterogeneity between years, between seasons within a year, between two fishing areas within the region, and between sexes. Analysis of molecular variation demonstrated slight, but significant, genetic divergence between collections of fish caught early and late in the season over the two years. These results are consistent with prior observations of Atlantic bluefin tuna of different conditions entering the fishery through the season, and suggest that the northeast Atlantic fishery represents a mixed-stock fishery including animals migrating from different areas and recruited from different spawning grounds.

scholarly journals The Economic Impact of Critical National Infrastructure Failure Due to Space Weather

2018 ◽  
Author(s):  
Edward J. Oughton
Keyword(s):  
Economic Impact ◽  
Space Weather ◽  
Time Series Data ◽  
Critical Infrastructure ◽  
Satellite Communications ◽  
Series Data ◽  
Future Research ◽  
Wide Range ◽  
Infrastructure Failure ◽  
National Infrastructure

Space weather is a collective term for different solar or space phenomena that can detrimentally affect technology. However, current understanding of space weather hazards is still relatively embryonic in comparison to terrestrial natural hazards such as hurricanes, earthquakes, or tsunamis. Indeed, certain types of space weather such as large Coronal Mass Ejections (CMEs) are an archetypal example of a low-probability, high-severity hazard. Few major events, short time-series data, and the lack of consensus regarding the potential impacts on critical infrastructure have hampered the economic impact assessment of space weather. Yet, space weather has the potential to disrupt a wide range of Critical National Infrastructure (CNI) systems including electricity transmission, satellite communications and positioning, aviation, and rail transportation. In the early 21st century, there has been growing interest in these potential economic and societal impacts. Estimates range from millions of dollars of equipment damage from the Quebec 1989 event, to some analysts asserting that losses will be in the billions of dollars in the wider economy from potential future disaster scenarios. Hence, the origin and development of the socioeconomic evaluation of space weather is tracked, from 1989 to 2017, and future research directions for the field are articulated. Since 1989, many economic analyzes of space weather hazards have often completely overlooked the physical impacts on infrastructure assets and the topology of different infrastructure networks. Moreover, too many studies have relied on qualitative assumptions about the vulnerability of CNI. By modeling both the vulnerability of critical infrastructure and the socioeconomic impacts of failure, the total potential impacts of space weather can be estimated, providing vital information for decision makers in government and industry. Efforts on this subject have historically been relatively piecemeal, which has led to little exploration of model sensitivities, particularly in relation to different assumption sets about infrastructure failure and restoration. Improvements may be expedited in this research area by open-sourcing model code, increasing the existing level of data sharing, and improving multidisciplinary research collaborations between scientists, engineers, and economists.

scholarly journals Temporal distribution of size and weight of fattened Bluefin tuna (Thunnus thynnus l.) from Tunisian farms: (2005-2010)

2013 ◽  
Vol 15 (1) ◽  
pp. 115 ◽  
Author(s):  
A. HATTOUR ◽  
W. KOCHED
Keyword(s):  
Fork Length ◽  
Weighted Average ◽  
Temporal Distribution ◽  
Bluefin Tuna ◽  
Thunnus Thynnus ◽  
Length Frequency ◽  
Average Value ◽  
Atlantic Bluefin Tuna ◽  
Straight Line ◽  
The Mean

The present study analysis size and weight-frequency composition of Atlantic bluefin tuna (Thunnus thynnus thynnus) fattened in Tunisian farms for the period 2005-2010 and compare these morphometric parameters with those from wild bluefin tuna landed on 2001 at Sfax port (Tunisia). A total of 6,757 wild and fattened bluefin tuna were measured as straight-line fork length and 49,962 were weighted. Average value of K for wild BFT was 1.59 and respectively 2.43, 2.32, 2.15, 1.61, 1.79 and 1.90 for Fattened BFT after 5-6 months from 2005 to 2010. Length frequency of fattened bluefin showed clearly a substantial increase in juvenile rate. The percentage which was 21.4% in 2005 reached 31.3% in 2009. For weight distribution, 73.3% of the fish caught in 2001 are below the annual mean (75.7 kg), while means 71 to 72% of fattened fish were under annual mean weight. Year 2009 is exceptional because only 57% of fattened fish were under the mean weight. This demonstrates that the fish caught are becoming increasingly small. Mean weight for fattening period (77 to 124 kg) are obviously higher than those of the wild fish (75,7kg).This study showed an increment in the amount of specimen under first sexual maturity which will not have the chance to spawn.

scholarly journals Surfacing and vertical behaviour of Atlantic bluefin tuna (Thunnus thynnus) in the Mediterranean Sea: implications for aerial surveys

2020 ◽  
Vol 77 (5) ◽  
pp. 1979-1991
Author(s):  
Robert Klaus Bauer ◽  
Fabien Forget ◽  
Jean-Marc Fromentin ◽  
Manuela Capello
Keyword(s):  
Mediterranean Sea ◽  
Fork Length ◽  
Bluefin Tuna ◽  
Aerial Survey ◽  
Thunnus Thynnus ◽  
Survey Period ◽  
Atlantic Bluefin Tuna ◽  
Aerial Surveys ◽  
Gulf Of Lion ◽  
Nw Mediterranean

Abstract Atlantic bluefin tuna (Thunnus thynnus) (ABFT) frequently engage in surface basking and foraging behaviour that makes them detectable from afar. This behaviour is utilized for the development of fisheries-independent abundance indices based on aerial surveys, although changes in the surface-feeding dynamics of ABFT are not yet accounted for. We investigated the daytime surfacing behaviour of ABFT at different temporal and vertical resolutions based on 24 individuals (117–158 cm fork length), tagged with pop-up archival tags in the Gulf of Lion, NW-Mediterranean Sea between 2015 and 2016. The results suggest that ABFT remain usually <2 min continuously within the visible surface (0–1 m) during daytime. ABFT presence in the 0–1 and 0–20 m layers varied over time and between individuals but showed a seasonal decline towards autumn with the breakdown of thermal stratification. Furthermore, the rate of surfacing events was highly correlated with the time spent in the 0–20 m layer. Geolocation estimates confirm a strong site fidelity of ABFT during the aerial survey period (August–October) in the Gulf of Lion. Our results support the choice of the survey region and period, but related indices should account for the seasonality of ABFT surface behaviour [i.e. the time spent in the 0–20 m layer.

A sequential Bayesian methodology to estimate movement and exploitation rates using electronic and conventional tag data: application to Atlantic bluefin tuna (Thunnus thynnus)

2009 ◽  
Vol 66 (2) ◽  
pp. 321-342 ◽  
Author(s):  
Hiroyuki Kurota ◽  
Murdoch K. McAllister ◽  
Gareth L. Lawson ◽  
Jacob I. Nogueira ◽  
Steven L.H. Teo ◽  
...  
Keyword(s):  
Auxiliary Information ◽  
Bluefin Tuna ◽  
Mortality Rates ◽  
Fishing Mortality ◽  
Thunnus Thynnus ◽  
Multiple Sources ◽  
The West ◽  
Movement Rates ◽  
Bayesian Methodology ◽  
Atlantic Bluefin Tuna

This paper presents a Bayesian methodology to estimate fishing mortality rates and transoceanic migration rates of highly migratory pelagic fishes that integrates multiple sources of tagging data and auxiliary information from prior knowledge. Exploitation rates and movement rates for Atlantic bluefin tuna ( Thunnus thynnus ) are estimated by fitting a spatially structured model to three types of data obtained from pop-up satellite, archival, and conventional tags for the period 1990–2006 in the western North Atlantic. A sequential Bayesian statistical approach is applied in which the key components of the model are separated and fitted sequentially to data sets pertinent to each component with the posterior probability density function (pdf) of parameters from one analysis serving as the prior pdf for the next. The approach sequentially updates the estimates of age-specific fishing mortality rates (F) and transoceanic movement rates (T). Estimates of recent F are higher than the estimated rate of natural mortality and higher in the east than in the west. Estimates of annual T from the west to the east are higher for larger fish (6% for ages 0–3 to 16% for ages 9+). These estimates are also higher than those obtained from tagging studies before the 1990s and could be associated with changes in stock composition.

Municipal changes in Slovakia. The evidence from spatial data.

2020 ◽  
Vol 11 (1) ◽  
pp. 58-72
Author(s):  
Martin MARIS
Keyword(s):  
Spatial Data ◽  
Time Series Data ◽  
Population Sample ◽  
Series Data ◽  
Annual Growth Rate ◽  
The West ◽  
Compound Annual Growth Rate ◽  
Fast Growing ◽  
The North ◽  
Statistical Criteria

The main objective of the paper is to examine the evolution of spatial patterns of settlement network in Slovakia as a result of population rearrangement among municipalities based on time series data of 1993 - 2017. The objects of the research are municipalities, which during the searched period recorded unusual fast population growth or decline, far exceeding the chosen parameter of the population sample. The primary population sample consists of 2919 municipalities. The experimental samples consist of 563 of fast-growing municipalities and 413 of fast-declining municipalities, based on the chosen statistical criteria, what is the compound annual growth rate. The results have shown that fast-growing municipalities are predominantly situated on the West, surrounding the Bratislava agglomeration, on the North and the East surrounding the Kosice metropolis. Generally, they tend to cluster around the cities on the district and regional levels. Fast-declining municipalities predominantly situated in the Middle, along the Hungarian, Polish, and Ukrainian border on the South and the East of the country, respectively.

Projections of future habitat use by Atlantic bluefin tuna: mechanistic vs. correlative distribution models

2016 ◽  
Vol 74 (3) ◽  
pp. 698-716 ◽  
Author(s):  
Barbara A. Muhling ◽  
Richard Brill ◽  
John T. Lamkin ◽  
Mitchell A. Roffer ◽  
Sang-Ki Lee ◽  
...  
Keyword(s):  
Climate Change ◽  
North Atlantic ◽  
Species Distribution Model ◽  
Bluefin Tuna ◽  
Distribution Model ◽  
Balance Model ◽  
Oxygen Balance ◽  
Spatiotemporal Resolution ◽  
Atlantic Bluefin Tuna ◽  
Fishing Fleets

Climate change is likely to drive complex shifts in the distribution and ecology of marine species. Projections of future changes may vary, however, depending on the biological impact model used. In this study, we compared a correlative species distribution model and a simple mechanistic oxygen balance model for Atlantic bluefin tuna (Thunnus thynnus: ABFT) in the North Atlantic Ocean. Both models gave similar results for the recent historical time period, and suggested that ABFT generally occupy favourable metabolic habitats. Projections from an earth system model showed largely temperature-induced reductions in ABFT habitat in the tropical and sub-tropical Atlantic by 2100. However, the oxygen balance model showed more optimistic results in parts of the subpolar North Atlantic. This was partially due to an inherent ability to extrapolate beyond conditions currently encountered by pelagic longline fishing fleets. Projections included considerable uncertainty due to the simplicity of the biological models, and the coarse spatiotemporal resolution of the analyses. Despite these limitations, our results suggest that climate change is likely to increase metabolic stress on ABFT in sub-tropical habitats, but may improve habitat suitability in subpolar habitats, with implications for spawning and migratory behaviours, and availability to fishing fleets.

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