Figure 1.
Size distribution of tagged bluefin tuna at deployment between 1996–1999 (mean±sd; 198.3±16 cm CFL; n = 280; light grey bars), and 2002–2005 (203.2±19 cm CFL; n = 281; dark grey bars).
Dotted lines indicate corresponding means.
Table 1.
Deployment, recovery and position summary.
Figure 2.
Recovery positions of electronic archival tags (triangles) in western Atlantic (orange, n = 64, 226±21 cm CFL), eastern Atlantic (white, n = 13, 218.4±13 cm CFL), and Mediterranean Sea (yellow, n = 29, 234±17 cm CFL).
Line at the 45°meridian indicates the management line. Black arrow indicates location of tag deployments in North Carolina. Large triangles with inset indicate locations of multiple recoveries. The highest recapture rates for these western tagged bluefin tuna were obtained from the region off New England (48% of total recaptures) followed by the Mediterranean Sea (27%). The Central and Northeast Atlantic emerged as the third area of high recovery (13%).
Figure 3.
Maps showing calculation of utilization distribution from pooled geolocation tracks.
Dark grey line at 45° meridian indicates management line. (a) Blue circles are all deployment, daily geolocation and recapture positions (n = 7,793) from 106 bluefin tuna between 1996–2006 and light blue circles indicate daily, linearly interpolated positions (n = 14,716) (b) Kernel density grid of resampled daily positions (n = 1,471,600). (c) Grid of number of bluefin tuna tracked per square kilometer. Blue line outlines area of ≥3 tags. (d) Normalized kernel density grid of number of daily geolocations weighted by number of fish tracked per unit area. Black, dotted line outlines 25% utilization distributions, showing four regions of high residency throughout the North Atlantic.
Figure 4.
Seasonal utilization distributions of bluefin tuna in western resident migration cycle (n = 49, 224±16 cm CFL).
Black arrows in ocean depict general direction of movements during relevant season. a) Winter. Grey arrow in North Carolina depicts approximate deployment location. b) Spring c) Summer d) Fall.
Figure 5.
Seasonal utilization distributions of bluefin tuna in trans-Atlantic movement pattern (n = 21, 232±14 cm CFL).
Black arrows in ocean depict general direction of movements during relevant season. (a) Winter. Grey arrow in North Carolina depicts approximate deployment location. (b) Spring (c) Summer (d) Fall.
Figure 6.
Mean (±SD) monthly number of days that bluefin tuna were present (1996–2005) within high use areas (grey shaded) in relation to mean (±SD) monthly level of primary productivity (green line) and sea surface temperature (blue line).
(a) Nortwest Atlantic (n = 32) (b) Nortwestern Corner (n = 5) (c) Carolina (n = 52) (d) Iberian Peninsula (n = 4).
Table 2.
Descriptive statistics for functional recovered archival tags with timeseries data (n = 44, 184–276 cm CFL).
Figure 7.
Typical diving behavior, external and internal temperature in the high use area of North Carolina.
(a) One month of a typical diving behavior (black) profile displayed with external (blue) and internal temperature (red) (WC98-485). Grey shades indicate nighttimes obtained through light level data. (b) Overall depth (left,black histogram) and ambient temperature (right, blue histogram) preferences in the high use area of North Carolina (1997–2005; n = 50).
Figure 8.
Typical diving behavior, external and internal temperature in the high use area of New England.
(a) One month of a typical diving behavior (black) profile displayed with external (blue) and internal temperature (red) (WC98-521). Grey shaded region indicates nighttime obtained through light level data . (b) Overall yearly depth (left, black histogram) and ambient temperature (right, blue histogram) preferences in the high use area of the Northwest Atlantic (1997–2005, n = 26).
Figure 9.
Typical diving behavior, external and internal temperature in the high use area of the North West Corner.
(a) One month of a typical diving behavior (black) profile displayed with external (blue) and internal temperature (red) (WC98-485). Grey shades indicate nighttimes obtained through light data . (b) Overall yearly depth (left,black histogram) and ambient temperature (right,blue histogram) preferences in the aggregation area of the North West Corner (1999–2000; 2004, n = 4).
Table 3.
Summary of residency and composition of tracked ABFT as well as diving and temperature indexes within particular high use area and non-high use areas (1996–2005, mean±sd).
Figure 10.
(a)–(b) Monthly geolocation estimates and track of individual Atlantic bluefin tuna with corresponding depth and temperature profiles indicating maximum diving behavior in relation to water temperature.
Black boxes indicate geographic regions covered by profiles. White arrow indicates deployment location. Black line in depth/temperature profiles indicates estimated depth of thermocline. (a) Bluefin in North Atlantic resident migration (98–485). Section 1: North Carolina, 2: off offshore Iberian Peninsula, 3: in North Western Corner, 4: northern Caribbean, 5: East Atlantic passing through Azores. (b) Bluefin in western resident migration (98–508). Section 1: North Carolina, 2: south off New Foundland & Novia Scotia, 3: offshore New England, Gulf of Maine, Fundian Channel and then Georges Bank. (c)–(f) Examples of depth/temperature profiles of fish in various migration phases. (c) & (d) WRS (744 & 1021); (e) TRANS and North Atlantic residency (98–504); (f) WRS & TRANS (1016) with entry into the Mediterranean Sea in July.
Figure 11.
Example of relationship between mean daily diving depth (grey circles) and corresponding mean daily depth of estimated thermocline (blue line) for one fish (WC98-508; LSFR, R2 = 0.92; P<0.0001).