vertical habitat use and diving behaviour of yellowfin...
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Vertical habitat use and diving behaviour of yellowfin tuna, Thunnus albacares, in CABO VERDE
Pericles Silva1, Ivanice Monteiro, Victor Stiebens,
Matthias Schabe, Heino O. Fock
1INDP; Mindelo – Sao Vincente, Cabo Verde
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Framework
• WP12 Environmental and anthropogenic pressures on pelagic ecosystems and fisheries
• Area affected by clime change (OMZ)
• Few data exist about characterization of how most pelagic species actually utilize water depths (Block et al., 1998; Brill and Lutcavage, 2001; Sibert and Nielsen, 2001 in Prince E. D. et al, 2006).
• High-oxygen-demand (≥3.5 ml l −1) (Stramma et al, 2010)
Main Goal
• Understand the environmental and anthropogenic pressures on pelagic fish in the tropical Atlantic - Vertical habitat use and diving behaviour
Tuna tagging campaign from 2014 to 2016 by TI and INDP.
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Spatial distribution of CPUE for YFT using deep LLs overlaid on SST images for the four quarters (mean value for 1998 – 2007)
(Lan et al, 2011) Framework
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Methodology • All fish were captured by means of hand line fishing and of rod fishing, applying circle
hooks or J-hooks, depending on the fishermen's experience in using circle hooks.
4 Yellow fin tuna tagged in 2016 with External pop-up satellite tags (Wildlife Computers MiniPAT) .
• 13 April 2016, on Maio Island (SF1).
• SF3 was deployed 1 Agoust south of São Nicolau island.
• Tuna 20.09.2016/Boavista_Piko_D_Home 16°05.667 23°02.012
• Tuna 17.10.2016/Boavista_West 16°10.046 23°01.564
Temp. Depth Light
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Results
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Results
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SF3
SF1
Results
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Results
PREDATION EVENT!!!?
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Short fin mako shark (Isurus oxyrinchus) (http://www.iucnredlist.org/details/39341/0)
Diet The diet of Shortfin Makos has been reported to consist mainly of teleost fishes (including mackerels, tunas, bonitos and other scombrids, anchovies,, swordfish)
all oceans from about 50°N (up to 60°N in the northeast Atlantic) to 50°S
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(Stramma et al, 2012)
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Summary
• Remaining in surface and mixed layer and thermocline
• Stayed at temperatures wormer then 14 ͦC to 16 ͦC well above temperature minimum of 10 ͦC (weng et al, 2009) because Oxygen could be more limiting then temperature.
• Results are consistent with the results of earlier studies conducted on T. albacares in other oceans.
• Further analyses to be done