Gross metabolic waste output estimates using a nutritional approach in Atlantic bluefin tuna (Thunnus thynnus) under intensive fattening conditions in western Mediterranean Sea

Abstract Atlantic bluefin tuna (Thunnus thynnus) (ABFT) frequently engage in surface basking and foraging behaviour that makes them detectable from afar. This behaviour is utilized for the development of fisheries-independent abundance indices based on aerial surveys, although changes in the surface-feeding dynamics of ABFT are not yet accounted for. We investigated the daytime surfacing behaviour of ABFT at different temporal and vertical resolutions based on 24 individuals (117–158 cm fork length), tagged with pop-up archival tags in the Gulf of Lion, NW-Mediterranean Sea between 2015 and 2016. The results suggest that ABFT remain usually <2 min continuously within the visible surface (0–1 m) during daytime. ABFT presence in the 0–1 and 0–20 m layers varied over time and between individuals but showed a seasonal decline towards autumn with the breakdown of thermal stratification. Furthermore, the rate of surfacing events was highly correlated with the time spent in the 0–20 m layer. Geolocation estimates confirm a strong site fidelity of ABFT during the aerial survey period (August–October) in the Gulf of Lion. Our results support the choice of the survey region and period, but related indices should account for the seasonality of ABFT surface behaviour [i.e. the time spent in the 0–20 m layer.

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Habitat use, vertical and horizontal behaviour of Atlantic bluefin tuna ( Thunnus thynnus ) in the Northwestern Mediterranean Sea in relation to oceanographic conditions

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2017.04.006 ◽

2017 ◽

Vol 141 ◽

pp. 248-261 ◽

Cited By ~ 4

Author(s):

Robert Klaus Bauer ◽

Jean-Marc Fromentin ◽

Hervé Demarcq ◽

Sylvain Bonhommeau

Keyword(s):

Habitat Use ◽

Mediterranean Sea ◽

Bluefin Tuna ◽

Thunnus Thynnus ◽

Atlantic Bluefin Tuna ◽

Northwestern Mediterranean Sea ◽

Oceanographic Conditions ◽

Northwestern Mediterranean

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Biometric characteristics of small Atlantic bluefin tuna (Thunnus thynnus, Linnaeus, 1758) of Mediterranean Sea origin

Journal of Applied Ichthyology ◽

10.1111/j.1439-0426.2011.01752.x ◽

2011 ◽

Vol 27 (4) ◽

pp. 971-976 ◽

Cited By ~ 4

Author(s):

V. Tičina ◽

L. Grubišić ◽

T. Šegvić Bubić ◽

I. Katavić

Keyword(s):

Mediterranean Sea ◽

Bluefin Tuna ◽

Thunnus Thynnus ◽

Atlantic Bluefin Tuna

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Migration, residency, and homing of bluefin tuna in the western Mediterranean Sea

ICES Journal of Marine Science ◽

10.1093/icesjms/fst157 ◽

2013 ◽

Vol 71 (3) ◽

pp. 510-518 ◽

Cited By ~ 24

Author(s):

Jean-Marc Fromentin ◽

Daniel Lopuszanski

Keyword(s):

Mediterranean Sea ◽

Spatial Dynamics ◽

Bluefin Tuna ◽

Western Mediterranean ◽

Careful Consideration ◽

Mediterranean Coast ◽

Central Mediterranean ◽

The North ◽

Western Mediterranean Sea ◽

Local Enrichment

Abstract This study presents the results of an electronic tagging programme on mature Atlantic bluefin tuna (ABFT) that has been conducted since 2007 offshore of the French Mediterranean Coast. The spatial distributions of ABFT showed little year-to-year variation and the fish concentrated in a small area of the central northwestern Mediterranean, where they may stay for several months. The individual tracks display sinuous trajectories in this area, indicating the possibility of feeding behaviour. No fish went out to the North Atlantic, but several fish displayed some migration to the southern western Mediterranean Sea during winter and the central Mediterranean during the spawning season. The homing behaviour of one fish after a full year as well as the back and forth of several fish further indicates that this restricted feeding area is probably persistent from year to year. We hypothesize that this area could result from local enrichment due to permanent mesoscale oceanographic features related to the North Mediterranean Current and the North Balearic front. The option of a spatial management, through marine protected areas, for a highly migratory species, such as ABFT, thus deserves more careful consideration because those species displayed complex spatial dynamics (e.g. homing), and population structure (e.g. several subpopulations of different sizes).

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