|Author(s)||Royer Francois, Fromentin Jean-Marc, Gaspar P|
|Affiliation(s)||Collecte Localisat Satellites, Div Oceanog Spatiale, F-31526 Ramonville St Agne, France.
IFREMER, Ctr Rech Halieut Mediterraneen & Trop, F-34203 Sete, France.
|Source||Marine Ecology Progress Series (0171-8630) (Inter-research), 2004 , Vol. 269 , P. 249-263|
|WOS© Times Cited||82|
|Keyword(s)||Thunnus thynnus, Gulf of Lions, point process analysis, front detection, sea surface temperature, ocean colour, aggregation|
|Abstract||We present an analysis of the distribution of bluefin tuna Thunnus thynnus schools spotted during aerial surveys in the Gulf of Lions, in relation to oceanographic features. Bio-optical and thermal properties of the sea surface derived from high-resolution sensors (AVHRR and SeaWiFS) were studied on a daily basis, and an edge-detection technique was applied to detect frontal zones. Geostatistics and point-process analyses were used to evaluate the role of the environment in structuring the spatial pattern of bluefin tuna (BFT). The distribution of schools spotted was strongly non-stationary both in space and time; this is believed to be an effect of the survey design (transect sampling) and the influence of transient oceanographic structures (surface fronts and eddies). The empirical variograms indicated a spatial range of the BFT schools at around 40 km, with substantial daily variability. Ripley's K statistic, as well as autocorrelation plots, revealed that the fish schools were clustered over a wider range of scales (from 10 to 80 km), indicating more spatial structure than would be expected from a random process. Finally, BFT school distributions appeared well determined by the oceanic features, except at very small scales (<10 km), where over-aggregation occurred, and at the largest scales of our study (>40 km), where over-spreading was detected. Dynamical ecological processes, such as foraging, are likely to induce this complex spatial pattern. Possible reasons for the association of tuna with fronts are presented.|
Royer Francois, Fromentin Jean-Marc, Gaspar P (2004). Association between bluefin tuna schools and oceanic features in the western Mediterranean. Marine Ecology Progress Series, 269, 249-263. Publisher's official version : https://doi.org/10.3354/meps269249 , Open Access version : https://archimer.ifremer.fr/doc/00000/10786/