scholarly journals Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean

2011 ◽  
Vol 68 (6) ◽  
pp. 1063-1071 ◽  
Author(s):  
Kuo-Wei Lan ◽  
Ming-An Lee ◽  
Hsueh-Jung Lu ◽  
Wei-Juan Shieh ◽  
Wei-Kuan Lin ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Net Primary Productivity ◽  
Principal Component ◽  
Yellowfin Tuna ◽  
Subsurface Water ◽  
Thunnus Albacares ◽  
Equatorial Atlantic ◽  
Catch Per Unit Effort ◽  
The North ◽  
Equatorial Atlantic Ocean

Abstract Lan, K-W., Lee, M-A., Lu, H-J., Shieh, W-J., Lin, W-K., and Kao, S-C. 2011. Ocean variations associated with fishing conditions for yellowfin tuna (Thunnus albacares) in the equatorial Atlantic Ocean. – ICES Journal of Marine Science, 68: 1063–1071. In this study, the Taiwanese longline (LL) fishery data were divided into two types: regular LL and deep LL. Furthermore, we collected environmental variables, such as sea surface temperature (SST), subsurface temperature, chlorophyll a concentration, net primary productivity, windspeed, and the north tropical Atlantic SST index (NTA) during the period 1998–2007 to investigate the relationship between LL catch data and oceanic environmental factors using principal component analysis (PCA). After the daily LL was separated into two types of LL, the results indicated that the deep LL was the major fishery catching yellowfin tuna (YFT) in the equatorial Atlantic Ocean. In 2003–2005, especially in 2005, the monthly catch by deep LL was double those of other years. The spatial distribution of the nominal catch per unit effort (cpue) by deep LL showed the maximum aggregation of YFT in waters with temperature above 24–25°C. The YFT mainly aggregated in the equatorial Atlantic, extending east in the first and second quarters of the year. In the third quarter of the year, the SST decreased off West Africa and the YFT migrated westwards to 15°W. Results of PCA indicated that higher subsurface water temperatures resulted in a deeper thermocline and caused a higher cpue of YFT, but the influence of NTA on the cpue of YFT seemed to be insignificant.

Exploitation and movements of yellowfin tuna (Thunnus albacares) and bigeye tuna (T. obesus) tagged in the north-western Coral Sea

1998 ◽  
Vol 49 (6) ◽  
pp. 475 ◽  
Author(s):  
John Hampton ◽  
John Gunn
Keyword(s):  
Seasonal Pattern ◽  
Yellowfin Tuna ◽  
Thunnus Albacares ◽  
Bigeye Tuna ◽  
Catch Per Unit Effort ◽  
The North ◽  
Coral Sea ◽  
Release Area ◽  
Seasonal Signal ◽  
North Western

Yellowfin tuna (Thunnus albacares) and bigeye tuna (T. obesus) were tagged and released in the north-western Coral Sea off northern Queensland in 1991 and 1992. Over the next five years, recaptures were reported by Australian longline vessels based in Cairns and fishing in the release area, and by industrial tuna fleets fishing in the adjacent western Pacific region, thus demonstrating clear links between the tuna stocks in these areas. Some southerly movements of yellowfin, in particular, further suggested links with stocks supporting the longline fishery in the south-eastern Australian Fishing Zone. Bigeye tuna tag returns and catch per unit effort by Cairns-based longliners showed a strong seasonal signal, peaking in mid year. Yellowfin tag-return data displayed a similar, but weaker, seasonal pattern. The data were analysed by use of tag-attrition models with seasonally variable catchability and with two assumptions regarding changes in targeting of the two species by longliners during the study. Under both assumptions, the local exploitation rates for yellowfin are low: about 0.07 in 1996. For bigeye, the local exploitation rate in 1996 may have been as high as 0.30, warranting a cautious approach to further fishery expansion in this area.

scholarly journals Structural Evidences for Present-day Compressive Tectonics at the St. Peter and St. Paul Archipelago (Equatorial Atlantic Ocean)

2021 ◽  
Author(s):  
Thomas Campos ◽  
Kenji Motoki ◽  
Susanna Sichel ◽  
Leonardo Barão ◽  
Marcia Maia ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Average Rate ◽  
High Angle ◽  
Transform Fault ◽  
Equatorial Atlantic ◽  
Joint System ◽  
Conjugate System ◽  
The North ◽  
Equatorial Atlantic Ocean ◽  
Load Release

This paper discusses the tectonics of the St. Peter and St. Paul Archipelago (SPSPA) in the Equato-rial Atlantic Ocean, based on the joint-system geometry which show a North-South shorten-ing/transpressional uplift tectonism, is active leading to exhumation of the sub-oceanic mantle. These islets are the summits of a sigmoidal submarine ridge formed by mantle ultramafic rocks. The ridge is crossed by the principal transform deformation zone of the northern transform fault of the St. Paul Multifault System. The South flank ridge exposes serpentinized mantle perido-tites, while the North flank exposes strongly deformed/fractured ultramylonites, recording duc-tile and brittle deformation at lithospheric conditions. The SPSPA show multiple joint systems cutting mylonitic foliation of the exposed rocks, forming three main families: high-angle paral-lel joints of tectonic origin, serpentinization-related joints with random direction and load-release low-angle parallel joints. The tectonic joints show an average direction of N31°E and N28°W, forming a conjugate system with a N1ºW compression axes, coherent with a trans-pressive stress field. Accordingly, the earthquakes focal mechanism close to the islets also shows N-S compression. The previously reported active uplift with an average rate of 1.5 mm/year and the directions of the joint system here reported agreeing with a present-day active N-S compres-sive field at a high angle with the direction of the transform fault.

Sign in / Sign up

Export Citation Format

Share Document