Feeding habits of bigeye tuna (Thunnus obesus) in the North Pacific from 2011 to 2013

2018 ◽  
Vol 69 (4) ◽  
pp. 585 ◽  
Author(s):  
Seiji Ohshimo ◽  
Yuko Hiraoka ◽  
Takuya Sato ◽  
Sayaka Nakatsuka
Keyword(s):  
Transition Zone ◽  
Body Length ◽  
North Pacific ◽  
Prey Species ◽  
Feeding Habits ◽  
North Pacific Ocean ◽  
Bigeye Tuna ◽  
Thunnus Obesus ◽  
Bet Size ◽  
The Kuroshio

In the present study, we analysed the stomach contents of 585 bigeye tuna (BET; Thunnus obesus) caught in the Kuroshio–Oyashio transition zone, a high-productivity region in the western North Pacific Ocean, to describe feeding habits and prey size. We identified 46 prey species belonging to 40 genera. Fish otoliths and squid beaks found in stomachs were used to calculate prey body length and weight from allometric relationships. The percentage index of relative importance (%IRI) was calculated from the mean percentage of occurrence, number and weight of each prey species. Squid and fish were the main prey of BET in the sampling area and the highest %IRI prey species during the survey was Eucleoteuthis luminosa (luminous flying squid; 7.6%), followed by Gonatopsis makko (mako armhook squid; 4.8%) and Magnisudis atlantica (duckbill barracudina; 2.3%). The %IRI of E. luminosa decreased and that of M. atlantica increased with increasing BET body length. The size of prey fish increased with increasing BET size, whereas the size of prey squid was similar across BET size. The results indicate ontogenetic shifts in the feeding habits of BET in the study area. These data provide fundamental information that will improve our understanding of oceanic food webs in the Kuroshio–Oyashio transition zone, an important foraging area for many pelagic species.

Spatiotemporal variability in bigeye tuna (Thunnus obesus) dive behavior in the central North Pacific Ocean

2010 ◽  
Vol 86 (1-2) ◽  
pp. 81-93 ◽  
Author(s):  
Evan A. Howell ◽  
Donald R. Hawn ◽  
Jeffrey J. Polovina
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Spatiotemporal Variability ◽  
Bigeye Tuna ◽  
Dive Behavior ◽  
Thunnus Obesus ◽  
Central North Pacific

scholarly journals Investigating the Role of Ocean–Atmosphere Coupling in the North Pacific Ocean

2014 ◽  
Vol 27 (2) ◽  
pp. 592-606 ◽  
Author(s):  
Dimitry Smirnov ◽  
Matthew Newman ◽  
Michael A. Alexander
Keyword(s):  
North Pacific ◽  
Climate Model ◽  
North Pacific Ocean ◽  
Global Climate Model ◽  
The North ◽  
Sst Variability ◽  
Oceanic Forcing ◽  
Noise Forcing ◽  
The Kuroshio ◽  
The North Pacific

Abstract Air–sea interaction over the North Pacific is diagnosed using a simple, local coupled autoregressive model constructed from observed 7-day running-mean sea surface temperature (SST) and 2-m air temperature TA anomalies during the extended winter from the 1° × 1° objectively analyzed air–sea fluxes (OAFlux) dataset. Though the model is constructed from 1-week lag statistics, it successfully reproduces the observed anomaly evolution through lead times of 90 days, allowing an estimation of the relative roles of coupling and internal atmospheric and oceanic forcing upon North Pacific SSTs. It is found that east of the date line, SST variability is maintained by, but has little effect on, TA variability. However, in the Kuroshio–Oyashio confluence and extension region, about half of the SST variability is independent of TA, driven instead by SST noise forcing internal to the ocean. Including surface zonal winds in the analysis does not alter this conclusion, suggesting TA adequately represents the atmosphere. Repeating the analysis with the output of two control simulations from a fully coupled global climate model (GCM) differing only in their ocean resolution yields qualitatively similar results. However, for the simulation employing the coarse-resolution (1°) ocean model, all SST variability depends upon TA, apparently caused by a near absence of ocean-induced noise forcing. Collectively, these results imply that a strong contribution from internal oceanic forcing drives SST variability in the Kuroshio–Oyashio region, which may be used as a justification for atmospheric GCM experiments forced with SST anomalies in that region alone. This conclusion is unaffected by increasing the dimensionality of the model to allow for intrabasin interaction.

scholarly journals Radiocarbon in the Water Column of the Southwestern North Pacific Ocean—24 Years After Geosecs

Radiocarbon ◽  
2004 ◽  
Vol 46 (2) ◽  
pp. 583-594 ◽  
Author(s):  
Pavel P Povinec ◽  
Takafumi Aramaki ◽  
George S Burr ◽  
A J Timothy Jull ◽  
Laval Liong Wee Kwong ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Kuroshio Extension ◽  
Kuroshio Current ◽  
Intermediate Water ◽  
North Pacific Intermediate Water ◽  
Deep Waters ◽  
Marine Radioactivity ◽  
The Kuroshio

In the framework of the Worldwide Marine Radioactivity Studies (WOMARS) project, water profile samples for radiocarbon measurements were taken during the IAEA'97 cruise at 10 stations in the southwestern North Pacific Ocean. While 14C concentrations were rapidly decreasing from the surface (Δ14C about 100‰) down to about 800 m at all visited stations (Δ14C about −200‰), the concentrations below 1000 m were almost constant. Some stations were in proximity to the GEOSECS stations sampled in 1973; thus, 14C profiles could be compared after a 24-yr interval. Generally, 14C concentrations had decreased in surface waters (by 50–80‰) and increased (by about the same amount) in intermediate waters when compared with GEOSECS data. In deep waters (below 1000 m), the observed 14C concentrations were similar to GEOSECS values. The bomb-produced 14C inventory had increased by more than 20% over the 24 yr from 1973 to 1997 and was estimated to be about (32 ± 5) 1012 atom m-2, with an annual 14C flux of (1.3 ± 0.3) 1012 atom m-2 yr-1. The results suggest that bomb-produced 14C has been advected northwards by the Kuroshio Current and the Kuroshio Extension and stored in the intermediate layer as North Pacific Intermediate Water.

scholarly journals Kuroshio Extension Variability and Forcing of the Pacific Decadal Oscillations: Responses and Potential Feedback

2003 ◽  
Vol 33 (12) ◽  
pp. 2465-2482 ◽  
Author(s):  
Bo Qiu
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Large Scale ◽  
North Pacific Ocean ◽  
Kuroshio Extension ◽  
Atmospheric Forcing ◽  
Mean Flow ◽  
Wind Stress Curl ◽  
The Pacific ◽  
The Kuroshio

Abstract A forcing mechanism is sought for the large-scale circulation changes in the Kuroshio Extension region of the western North Pacific Ocean as inferred by TOPEX/Poseidon sea surface height (SSH) data. The low-frequency signal of the Kuroshio Extension over the last decade was characterized by a modulation in its zonal mean flow intensity: the mean Kuroshio Extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997. The ability to simulate the major trends in the observed SSH signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern North Pacific Ocean related to the Pacific decadal oscillations (PDOs). To be specific, the weakening (strengthening) trend in 1993–96 (1997–2001) was caused by westward expansions of negative (positive) SSH anomalies south of the Kuroshio Extension and positive (negative) SSH anomalies north of the Kuroshio Extension. Emergence of oppositely signed SSH anomalies on the two sides of the Kuroshio Extension jet is due to the different propagating speeds of the baroclinic Rossby waves, which carry the wind-induced SSH anomalies generated in the eastern North Pacific at different phases of the PDOs. Hindcasting the Kuroshio Extension jet strength over the last 45 years reveals that the jet modulation has a dominant timescale of ∼12 yr. Given the location of the Kuroshio Extension jet relative to the maximum atmospheric forcing, it is found that this dominant timescale is consistent with the preferred timescale under a stochastic white-noise atmospheric forcing. It is hypothesized that this connection between the Kuroshio Extension strength and the latitudinally dependent baroclinic adjustment contributes to an increase in variance and persistence of the North Pacific midlatitude coupled system on the decadal timescale.

Floating plastic in the Kuroshio Current area, western North Pacific Ocean

2007 ◽  
Vol 54 (4) ◽  
pp. 485-488 ◽  
Author(s):  
Rei Yamashita ◽  
Atsushi Tanimura
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Kuroshio Current ◽  
Western North Pacific Ocean ◽  
Current Area ◽  
The Kuroshio
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