Fig. 1

Daily average solar panel and capacitor voltage (a), minimum daily temperature (b), and daily maximum ΔT min⁻¹ (c) for the 15 Atlantic bluefin tuna for which tag data were recovered. Short horizontal solid lines represent the mean daily summary values for each fish. The horizontal dashed lines in a refer to the maximum and minimum solar capacitor voltages (3.6 and 2.2 V); the horizontal dashed line in b refers to the minimum temperature threshold for pop-off (4.5 °C); the horizontal dashed line in c refers to the daily maximum ΔT min⁻¹ threshold for pop-off (72 h at less than 0.2 °C). The black diamonds for Fish #12 correspond to the daily summary data from when the tag/fish were presumably inside a lamnid shark, characterized by darkness (reflected by low solar panel voltage), a high minimum temperature, and a low daily maximum ΔT min⁻¹