scholarly journals Genetic validation of the unexpected presence of a tropical tuna, bigeye tuna ( Thunnus obesus ), in the Mediterranean

2021 ◽  
Author(s):  
Nuria Pérez Bielsa ◽  
Judith Ollé ◽  
David Macías ◽  
Sámar Saber ◽  
Jordi Viñas
Keyword(s):  
Bigeye Tuna ◽  
Thunnus Obesus ◽  
The Mediterranean ◽  
Tropical Tuna

scholarly journals In situ target strength of bigeye tuna (Thunnus obesus) associated with fish aggregating devices

2019 ◽  
Author(s):  
G Boyra ◽  
G Moreno ◽  
B Orue ◽  
B Sobradillo ◽  
I Sancristobal
Keyword(s):  
Frequency Response ◽  
Target Strength ◽  
Species Discrimination ◽  
Bigeye Tuna ◽  
Central Pacific ◽  
Commercial Fish ◽  
Thunnus Obesus ◽  
Tropical Tuna ◽  
Fish Aggregating Devices

Abstract Bigeye tuna (Thunnus obesus) is an important commercial fish species, which aggregates around fish aggregating devices (FADs) together with other tropical tuna species. Acoustics is the main technology used by fishers and scientists for the location and quantification of tunas at FADs. However, currently it is not possible to reliably discriminate between the different tropical tuna species that are found together at FADs using acoustic methods, which hampers the development of selective fishing needed to preserve some of the tropical tuna species for which overfishing is occurring. One of the prerequisites for species discrimination is to know the target strength (TS) of each species at different frequencies. This paper measures in situ TS values and explores the frequency response of bigeye tuna at FADs in the central Pacific Ocean using three different acoustic frequencies. For the range of body length caught (40–100 cm), the obtained b20 values were −65, −66, and −72 dB for 38, 120, and 200 kHz, respectively. The decreasing frequency response pattern obtained for this swimbladder bearing species contrasts with the opposite pattern previously observed for skipjack tuna (bladder-less), the most abundant tuna species found at FADs, hence allowing the potential for discrimination between the two species.

QUANTIFICATION OF TUNA FISH TARGET STRENGTH USING QUANTITATIVE ECHO SOUNDER

2009 ◽  
Vol 1 (1) ◽  
Author(s):  
Henry M. Manik
Keyword(s):  
Wave Reflection ◽  
Fork Length ◽  
Research Programme ◽  
Yellowfin Tuna ◽  
Target Strength ◽  
Bigeye Tuna ◽  
Tuna Fish ◽  
Thunnus Obesus ◽  
The Relationship ◽  
Echo Sounder

A preliminary research programme was carried out in order to study the acoustic wave reflection or target strength (TS) of tuna fish using a quantitative echo sounder (QES). The relationships between TS to fork length (FL) and swimbladder volume, for bigeye tuna (Thunnus obesus) and yellowfin tuna (T. albacares) are investigated. The TS of bigeye tuna was about 3 dB higher than yellowfin tuna when comparing species at the same size. The result can be correlated to the swimbladder volume differencebetween species. The relationship between TS and swimbladder volume was quantified for both species.Keywords: tuna fish, target strength, quantitative echo sounder

Vertical distribution of bigeye tuna Thunnus obesus in the tropical Indian Ocean

2013 ◽  
Vol 20 (3) ◽  
pp. 660-671 ◽  
Author(s):  
Xuezhong CHEN ◽  
Shenglong YANG ◽  
Yu Zhang ◽  
Wei FAN ◽  
Yumei WU
Keyword(s):  
Indian Ocean ◽  
Vertical Distribution ◽  
Tropical Indian Ocean ◽  
Bigeye Tuna ◽  
Thunnus Obesus

scholarly journals Quantifying the increase in fishing efficiency due to the use of drifting FADs equipped with echosounders in tropical tuna purse seine fisheries

2020 ◽  
Author(s):  
Gwenaëlle Wain ◽  
Loreleï Guéry ◽  
David Michael Kaplan ◽  
Daniel Gaertner
Keyword(s):  
New Technology ◽  
Recent Change ◽  
Purse Seine ◽  
Catch Per Unit Effort ◽  
Katsuwonus Pelamis ◽  
Thunnus Obesus ◽  
Efficiency Increase ◽  
Tropical Tuna ◽  
Floating Objects ◽  
The Impact

Abstract Numerous pelagic species are known to associate with floating objects (FOBs), including tropical tunas. Purse seiners use this behaviour to facilitate the capture of tropical tunas by deploying artificial drifting fish aggregating devices (dFADs). One major recent change has been the integration of echosounders in satellite-tracked GPS buoys attached to FOBs, allowing fishers to remotely estimate fishable biomass. Understanding the effects of this new technology on catch of the three main tuna species (yellowfin tuna, Thunnus albacares; bigeye tuna, Thunnus obesus; and skipjack tuna, Katsuwonus pelamis) is important to accurately correct for this change in catch-per-unit-effort (CPUE) indices used for stock assessments. We analysed catch data from the French purse seine fleet for the period 2010–2017 in the Indian Ocean to assess the impact of this fleet’s switch to echosounder buoys around 2012. Results indicate that echosounders do not increase the probability a set will be succesful, but they have a positive effect on catch per set, with catches on average increasing by ≈2−2.5 tonnes per set (≈10%) when made on the vessel's own dFADs equipped with an echosounder buoy. Increases were due to a decrease in sets below ≈25 tonnes and an increase in those greater than ≈25 tonnes, with a non-linear transition around this threshold. This increase explains the considerable investment of purse seiners in echosounder buoys, but also raises concerns about bias in stock size estimates based on CPUE if we do not correct for this fishing efficiency increase.

Size-specific spatiotemporal dynamics of bigeye tuna (Thunnus obesus) caught by the longline fishery in the eastern Pacific Ocean

2021 ◽  
Vol 243 ◽  
pp. 106065
Author(s):  
Keisuke Satoh ◽  
Haikun Xu ◽  
Carolina V. Minte-Vera ◽  
Mark N. Maunder ◽  
Toshihide Kitakado
Keyword(s):  
Pacific Ocean ◽  
Spatiotemporal Dynamics ◽  
Eastern Pacific ◽  
Longline Fishery ◽  
Bigeye Tuna ◽  
Eastern Pacific Ocean ◽  
Thunnus Obesus

scholarly journals Age and growth estimation of bigeye tuna, Thunnus obesus (Teleostei: Scombridae) in the southwestern Atlantic

2012 ◽  
Vol 10 (1) ◽  
pp. 148-158 ◽  
Author(s):  
Paulo Duarte-Neto ◽  
Fábio M. Higa ◽  
Rosangela P. Lessa
Keyword(s):  
Fork Length ◽  
Age And Growth ◽  
Data Uncertainty ◽  
Bigeye Tuna ◽  
Western Atlantic ◽  
Thunnus Obesus ◽  
Marginal Increment ◽  
Back Calculation ◽  
Growth Estimation ◽  
Averaged Model

The purpose of the current study was to supply the first information on age and growth for Thunnus obesus caught in the equatorial south-western Atlantic using dorsal spines, an approach that has been successfully employed for ageing tuna species. The study was conducted using a multi-model inference based on information theory for back-calculated and observed length-at-age data. Uncertainty associated with the parameter estimation was verified and results were compared to other accounts on the species, considering both the statistical and methodological contexts. Samples were collected in Natal city (Rio Grande do Norte State, Brazil) from February 1999 to January 2000, of tuna vessels and from surveys, aimed at providing information on the Brazilian Exclusive Economic Zone (EEZ) in the area around São Pedro and São Paulo Archipelago. Validation using marginal increment indicated that one ring is deposited per year. Mean length-at-age ranged of 54.3 to 177.5 cm (fork length) for ages 1 to 9 years. Von Bertalanffy, Richards, and Gompertz models were considered suitable for the bigeye tuna. Hence, the model-averaged asymptotic length ¯L∞ was estimated. The averaged model generated in the present study by back-calculation was considered appropriate for describing the growth of T. obesus.

Microstructural modification and its effect on the quality attributes of frozen-thawed bigeye tuna (Thunnus obesus) meat during salting

LWT ◽  
2019 ◽  
Vol 100 ◽  
pp. 213-219 ◽  
Author(s):  
Qingqing Jiang ◽  
Naho Nakazawa ◽  
Yaqin Hu ◽  
Kazufumi Osako ◽  
Emiko Okazaki
Keyword(s):  
Quality Attributes ◽  
Bigeye Tuna ◽  
Microstructural Modification ◽  
Thunnus Obesus

scholarly journals Effects of El Niño–Southern Oscillation events on catches of Bigeye Tuna (Thunnus obesus) in the eastern Indian Ocean off Java

2013 ◽  
Vol 111 (2) ◽  
pp. 175-188 ◽  
Author(s):  
Mega L. Syamsuddin ◽  
Sei-Ichi Saitoh ◽  
Toru Hirawake ◽  
Samsul Bachri ◽  
Agung B. Harto
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Eastern Indian Ocean ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Bigeye Tuna ◽  
Thunnus Obesus
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