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.

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.

Internal Zonations in Sections of Vertebrae from Atlantic Bluefin Tuna, Thunnus thynnus, and Their Potential Use in Age Determination

1985 ◽  
Vol 42 (5) ◽  
pp. 938-946 ◽  
Author(s):  
Eric D. Prince ◽  
Dennis W. Lee ◽  
Joaquin C. Javech
Keyword(s):  
Age Groups ◽  
Age Determination ◽  
Fork Length ◽  
Bluefin Tuna ◽  
Age And Growth ◽  
Thunnus Thynnus ◽  
Thin Sections ◽  
Section Method ◽  
Atlantic Bluefin Tuna ◽  
Cone Surface

Internal zonations (bands) were observed in thin sections of vertebrae from 98% of the 200 Atlantic bluefin tuna, Thunnus thynnus, we examined between 49.5 and 284.5 cm fork length (FL). These zones occurred in the solid bone area of the sections corresponding to the outer margin of the vertebral cone surface. The remaining area of the section nearest the focus is characterized by spongy bone which obstructs internal zonations associated with early growth history. We present a modified method of determining vertebra age of Atlantic bluefin tuna by adopting a counting procedure which involves enumerating distal internal bands in the sections, as well as proximal external bands on the cone surface to assign ages. Accuracy of this methodology was assessed by evaluating fish where age was known from length frequency and tagging data. The accuracy and precision of estimating age of giant bluefin tuna [Formula: see text] was improved using our vertebral section method of age determination compared with the more traditional whole vertebra method of ageing. However, results of the vertebral section method in ageing medium tuna (146.0–208.9 cm FL) were inconclusive and this method overestimated age of school tuna (49.5–145.9 cm FL) and should not be used for juvenile age groups. The occurrence of internal zonations in vertebrae of teleosts other than bluefin tuna should be examined as a possible source of age and growth information.

Active prey selection in developing larvae of Atlantic bluefin tuna (Thunnus thynnus) in spawning grounds of the Gulf of Mexico

2021 ◽  
Author(s):  
Akihiro Shiroza ◽  
Estrella Malca ◽  
John T Lamkin ◽  
Trika Gerard ◽  
Michael R Landry ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Prey Selection ◽  
Bluefin Tuna ◽  
Gut Contents ◽  
Physical Factors ◽  
Larval Rearing ◽  
Thunnus Thynnus ◽  
Small Copepod ◽  
Atlantic Bluefin Tuna ◽  
Larval Stages

Abstract Bluefin tuna spawn in restricted areas of subtropical oligotrophic seas. Here, we investigate the zooplankton prey and feeding selectivity of early larval stages of Atlantic bluefin tuna (ABT, Thunnus thynnus) in larval rearing habitat of the Gulf of Mexico. Larvae and zooplankton were collected during two multi-day Lagrangian experiments during peak spawning in May 2017 and 2018. Larvae were categorized by flexion stage and standard length. We identified, enumerated and sized zooplankton from larval gut contents and in the ambient community. Ciliates were quantitatively important (up to 9%) in carbon-based diets of early larvae. As larvae grew, diet composition and prey selection shifted from small copepod nauplii and calanoid copepodites to larger podonid cladocerans, which accounted for up to 70% of ingested carbon. Even when cladoceran abundances were <0.2 m−3, they comprised 23% of postflexion stage diet. Feeding behaviors of larvae at different development stages were more specialized, and prey selection narrowed to appendicularians and primarily cladocerans when these taxa were more abundant. Our findings suggest that ABT larvae have the capacity to switch from passive selection, regulated by physical factors, to active selection of presumably energetically optimal prey.

Effects of local scale perturbations in the Atlantic bluefin tuna (Thunnus thynnus L.) trap fishery of Sardinia (W. Mediterranean)

2008 ◽  
Vol 92 (2-3) ◽  
pp. 242-254 ◽  
Author(s):  
Piero Addis ◽  
John Mark Dean ◽  
Paola Pesci ◽  
Ivan Locci ◽  
Rita Cannas ◽  
...  
Keyword(s):  
Bluefin Tuna ◽  
Local Scale ◽  
Thunnus Thynnus ◽  
Atlantic Bluefin Tuna ◽  
Trap Fishery

Notes on Age Determination and Growth of the Atlantic Bluefin Tuna, Thunnus thynnus (Linnaeus)

Copeia ◽  
1941 ◽  
Vol 1941 (2) ◽  
pp. 70 ◽  
Author(s):  
J. R. Westman ◽  
P. W. Gilbert
Keyword(s):  
Age Determination ◽  
Bluefin Tuna ◽  
Thunnus Thynnus ◽  
Atlantic Bluefin Tuna

scholarly journals Modeling the implications of stock mixing and life history uncertainty of Atlantic bluefin tuna

2017 ◽  
Vol 74 (11) ◽  
pp. 1990-2004 ◽  
Author(s):  
Lisa A. Kerr ◽  
Steven X. Cadrin ◽  
David H. Secor ◽  
Nathan G. Taylor
Keyword(s):  
Temporal Distribution ◽  
Bluefin Tuna ◽  
Analytical Framework ◽  
Magnitude Distribution ◽  
Atlantic Bluefin Tuna ◽  
Age Structured ◽  
Stock Mixing ◽  
Overlap Model ◽  
Mixed Stock ◽  
Central Atlantic

Atlantic bluefin tuna (Thunnus thynnus) is currently managed as two separate eastern and western stocks, despite information indicating considerable stock mixing. Using a simulation model, we explored how scenarios of population-specific migration and uncertainty in aspects of bluefin tuna biology affect the magnitude, distribution, and mixed stock nature of the resource and catch of its associated fisheries. The analytical framework was a stochastic, age-structured, stock-overlap model that was seasonally and spatially explicit with movement of eastern- and western-origin tuna informed by tagging and otolith chemistry data. Alternate estimates of movement and assumptions regarding maturity and recruitment regime for western-origin fish were considered. Simulation of the operating model indicated considerable stock mixing in the western and central Atlantic, which resulted in differences between the stock and population view of western bluefin tuna. The relative biomass of the western population and its spatial and temporal distribution in the Atlantic was sensitive to model assumptions and configurations. Simulation modeling can provide a means to ascertain the potential consequences of stock mixing on the assessment and management of fishery resources.

scholarly journals Atlantic Bluefin Tuna (Thunnus thynnus) Biometrics and Condition

PLoS ONE ◽  
2015 ◽  
Vol 10 (10) ◽  
pp. e0141478 ◽  
Author(s):  
Enrique Rodriguez-Marin ◽  
Mauricio Ortiz ◽  
José María Ortiz de Urbina ◽  
Pablo Quelle ◽  
John Walter ◽  
...  
Keyword(s):  
Bluefin Tuna ◽  
Thunnus Thynnus ◽  
Atlantic Bluefin Tuna
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