Fig 1.
Numbers represent the different tagging locations (1. Roses/Llançà, 2. Pollença, 3. Moraira, 4. Algeciras, 5. Strait of Bonifacio, 6. San Benedetto del Tronto, and 7. Porto Barricata).
Lines indicate the separation between the different Mediterranean basins based on FAO Fishing area criteria.
Table 1.
Summary information on the deployments of electronic tags (>22 days on fish)—from 2000–2012 on western Mediterranean and Adriatic Sea bluefin tuna, analyzed in this study.
Fig 2.
Daily positions based on estimated geolocation of the 38 tuna analyzed in this study and tagged within the Mediterranean Sea with pop-up satellite and archival tags.
White circles represent the positions of the tuna tagged in the western Mediterranean basin (n = 28 pop-up tags + 1 internal tag), while yellow circles represent the positions of the tuna tagged in the Adriatic (n = 9 pop-up tags).
Fig 3.
Daily positions for the 38 tuna analyzed in this study.
Orange circles represent the internally tagged fish, while the white circles are the positions of the tunas tagged with pop-up satellite tags in both basins.
Fig 4.
Longitude for internal tag #0890152 by year.
Table 2.
Deployment data and recapture information of the implanted internal tags deployed in 2008 in Roses, NE Spain.
Fig 5.
Seasonal Utilization Distributions (UDs) of bluefin tuna.
The locations of the tuna were examined for the (A) spawning period (i.e. May 15 to July 15) and the seasonal periods of (B) spring, (C) summer, (D) autumn and (E) winter. UDs were computed using the Kernel method through the ad hoc method (h = Sigma*n^(-1/6), Sigma = 0.5*(sd(x)+sd(y))). The graphs show the UDs cumulative frequencies up to 95% (the color attributed to a given percentage p applies to areas comprised between p and p–1% isopleths).
Fig 6.
Locations of bluefin tuna fishing operations between April and August in the Mediterranean Sea from 1989 to 2012 (n = 6031) (different color dots), and spatial distribution of the Japanese longliners’ total bluefin tuna catches in Algeria from 2000 to 2007 (based on Abdelhadi et al.,[69]) (red dotted line).
PS = Purse seiners, LL = Longliners and BB = Bait boats.
Fig 7.
Tagged bluefin tuna possibly engaging in spawning during the reproductive season.
Note: yellow squares indicate periods of time with low linearity values and possible spawning behavior.
Fig 8.
Linearity index for the four tags at liberty from mid-May to October.
Green #10P0402, red #10P0398, black #10P0546 and blue #10P0648.
Fig 9.
Dendrogram for tag #10P0648 determined from clustering analysis of differences in diving patterns Each column represents a 24-hours depth histogram (n = 175 days) and the color is the fraction of time.
The density variable is expressed as a fraction of each day spent in depth bins defined along the y-axis.
Fig 10.
(A). Positions of the different clusters along the track of the tuna 10P0648 (in Black cluster #1, green cluster #2, red cluster #3, blue cluster #4, yellow cluster #5, violet #6 and in white cluster #7).
(B) Kernel distribution of cluster 2 and 3 during May, June and July. Number #1 compiled the period from 25th May to 5 th June, #2 from 7th to 14th June while #3 is for 17th to 30th of June.
Table 3.
Mean values, maximums, minimums and standard deviation for the clusters obtained.
Table 4.
Mean values, maximums, minimums and standard deviation for cluster 2 and 3 for all months when present.
Fig 11.
Depth and temperature profiles #10P0648.
Dot line corresponds to mixed layer while a dashed line is the thermocline. (A) Cluster 2, the high oscillatory dives are present but do not break the mixed layer (16 June). (B) Cluster 2, high oscillatory dives going below the thermocline, followed by a “U”-shape dive (21 June). (C) Cluster 3 (consecutive day), same pattern but only a few “V”-shape dives during the rest of the day (22 June).
Fig 12.
Trajectory of tuna with tag ID # 10P0398
(A) June 16 to June 20 (pink dot and triangle, respectively) and (B) July 6 to July 10 (pink dot and triangle, respectively) plotted with the mean Sea Surface Salinity (SSS) and the mean geostrophic velocity (UV) for those specific days.
Table 5.
Satellite oceanographic parameters for the 4 bluefin tuna (BFT) during the proposed spawning periods of tunas with tag ID # 10P0398, 10P0546, 10P0648 and 10P0402.