Natal origin of Pacific bluefin tuna from the California Current Large Marine Ecosystem

Natal origin of subadult (age-1) Pacific bluefin tuna (PBT, Thunnus orientalis ) from the California Current Large Marine Ecosystem (CCLME) was determined using natural tracers in ear stones (otoliths). Age-0 PBT collected from the two known spawning areas in the western Pacific Ocean (East China Sea, Sea of Japan) were used to establish baseline signatures from otolith cores over 4 years (2014–2017) based on a suite of trace elements (Li, Mg, Mn, Sr, Zn and Ba). Distinct chemical signatures existed in the otolith cores of age-0 PBT collected from the two spawning areas, with overall classification accuracy ranging 73–93% by year. Subadult PBT collected in the CCLME over the following 4 years (2015–2018) were then age-class matched to baselines using mixed-stock analysis. Natal origin of trans-Pacific migrants in the CCLME ranged 43–78% from the East China Sea and 22–57% from the Sea of Japan, highlighting the importance of both spawning areas for PBT in the CCLME. This study provides the first estimates on the natal origin of subadult PBT in this ecosystem using otolith chemistry and expands upon the application of these natural tracers for population connectivity studies for this species.

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Natal Origin and Age-Specific Egress of Pacific Bluefin Tuna From Coastal Nurseries Revealed With Geochemical Markers

10.21203/rs.3.rs-199680/v1 ◽

2021 ◽

Author(s):

Jay R. Rooker ◽

R. J. David Wells ◽

Barbara A. Block ◽

Hui Liu ◽

Hannes Baumann ◽

...

Keyword(s):

East China Sea ◽

Sea Of Japan ◽

Marine Ecosystem ◽

Bluefin Tuna ◽

East China ◽

Pacific Bluefin Tuna ◽

The East China Sea ◽

China Sea ◽

Natal Origin ◽

Geochemical Profile

Abstract Geochemical chronologies were constructed from otoliths of adult Pacific bluefin tuna (PBT) to investigate the timing of age-specific egress of juveniles from coastal nurseries (natal sites) in the East China Sea or Sea of Japan to offshore waters of the Pacific Ocean. Element:Ca chronologies were developed for otolith Li:Ca, Mg:Ca, Mn:Ca, Zn:Ca, Sr:Ca, and Ba:Ca, and our assessment focused on the section of the otolith corresponding to the juvenile period (age-0 to age-1+). Next, we applied a common time-series approach (i.e., changepoint analysis) to geochemical profiles to identify divergences presumably linked to inshore-offshore migrations. Conspicuous geochemical shifts were detected during the juvenile interval for Mg:Ca, Mn:Ca, and Sr:Ca that were indicative of coastal-offshore transitions or egress generally occurring for individuals approximately 4-6 mo. old, with later departures (6 mo. or older) linked to overwintering being more limited. Changepoints in ototith Ba:Ca profiles were most common in the early age-1 period (ca. 12-16 mo.) and appear associated with entry into upwelling areas such as the California Current Large Marine Ecosystem following trans-Pacific migrations. Natal origin of PBT was also predicted using the early life portion of geochemical profile in relation to a baseline sample comprised of age-0 PBT from the two primary spawning areas in the East China Sea and Sea of Japan. Mixed-stock analysis indicated that the majority of adult PBT in our sample originated from the East China Sea, but individuals of Sea of Japan origin were also detected our sample of spawning adults collected in the Ryukyu Archipelago.

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Natal origin and age-specific egress of Pacific bluefin tuna from coastal nurseries revealed with geochemical markers

Scientific Reports ◽

10.1038/s41598-021-93298-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jay R. Rooker ◽

R. J. David Wells ◽

Barbara A. Block ◽

Hui Liu ◽

Hannes Baumann ◽

...

Keyword(s):

East China Sea ◽

Sea Of Japan ◽

Marine Ecosystem ◽

Bluefin Tuna ◽

East China ◽

Pacific Bluefin Tuna ◽

The East China Sea ◽

China Sea ◽

Natal Origin ◽

Geochemical Profile

AbstractGeochemical chronologies were constructed from otoliths of adult Pacific bluefin tuna (PBT) to investigate the timing of age-specific egress of juveniles from coastal nurseries in the East China Sea or Sea of Japan to offshore waters of the Pacific Ocean. Element:Ca chronologies were developed for otolith Li, Mg, Mn, Zn, Sr, and Ba, and our assessment focused on the section of the otolith corresponding to the age-0 to age-1 + interval. Next, we applied a common time-series approach to geochemical profiles to identify divergences presumably linked to inshore-offshore migrations. Conspicuous geochemical shifts were detected during the juvenile interval for Mg:Ca, Mn:Ca, and Sr:Ca that were indicative of coastal-offshore transitions or egress generally occurring for individuals approximately 4–6 mo. old, with later departures (6 mo. or older) linked to overwintering being more limited. Changepoints in otolith Ba:Ca profiles were most common in the early age-1 period (ca. 12–16 mo.) and appear associated with entry into upwelling areas such as the California Current Large Marine Ecosystem following trans-Pacific migrations. Natal origin of PBT was also predicted using the early life portion of geochemical profile in relation to a baseline sample comprised of age-0 PBT from the two primary spawning areas in the East China Sea and Sea of Japan. Mixed-stock analysis indicated that the majority (66%) of adult PBT in our sample originated from the East China Sea, but individuals of Sea of Japan origin were also detected in the Ryukyu Archipelago.

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Combining otolith microstructure and trace elemental analyses to infer the arrival of juvenile Pacific bluefin tuna in the California current ecosystem

ICES Journal of Marine Science ◽

10.1093/icesjms/fsv062 ◽

2015 ◽

Vol 72 (7) ◽

pp. 2128-2138 ◽

Cited By ~ 10

Author(s):

Hannes Baumann ◽

R. J. D. Wells ◽

Jay R. Rooker ◽

Saijin Zhang ◽

Zofia Baumann ◽

...

Keyword(s):

Marine Ecosystem ◽

Fork Length ◽

California Current ◽

Bluefin Tuna ◽

Otolith Microstructure ◽

Pacific Bluefin Tuna ◽

Thunnus Orientalis ◽

Trace Elemental ◽

Large Marine Ecosystem ◽

Age Estimates

Abstract Juvenile Pacific bluefin tuna (PBT, Thunnus orientalis) are known to migrate from western Pacific spawning grounds to their eastern Pacific nursery and feeding grounds in the California Current Large Marine Ecosystem (CCLME), but the timing, durations, and fraction of the population that makes these migrations need to be better understood for improved management. To complement recent work focused on stable isotope and radiotracer approaches (“tracer toolbox”; Madigan et al., 2014) we explored the suitability of combining longitudinal analyses of otolith microstructure and trace elemental composition in age ∼1–2 PBT (n = 24, 66–76 cm curved fork length) for inferring the arrival of individuals in the CCLME. Element:Ca ratios in transverse otolith sections (9–12 rows, triplicate ablations from primordium to edge, ø50 μm) were quantified for eight elements: Li, Mg, Mn, Co, Cu, Zn, Sr, and Ba, which was followed by microstructure analysis to provide age estimates corresponding to each ablation spot. Age estimates from otoliths ranged from 328 to 498 d post-hatch. The combined elemental signatures of four elements (Ba, Mg, Co, Cu) showed a significant increase at the otolith edge in approximately half of the individuals (30–60 d before catch). Given the different oceanographic properties of oligotrophic open Pacific vs. high nutrient, upwelling CCLME waters, this signal is consistent with the entry of the fish into the CCLME, which was estimated to occur primarily in July after a transoceanic migration of ∼1.5–2.0 months. Our approach comprises a useful addition to the available tracer toolbox and can provide additional and complementary understanding of trans-Pacific migration patterns in PBT.

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