Association of yellowfin tuna (Thunnus albacares) with tracking vessels during ultrasonic telemetry experiments


Dagorn, Laurent, Erwan Josse, and Pascal Bach
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Three yellowfin tuna (Thunnus albacares) carrying ultrasonic depth-sensitive transmitters developed a strong association with the tracking vessel, following it at speeds up to 5 knots (2.6 m/s). Two fish associated with the tracking vessel during daytime, and the other fish during day and night periods. Swimming behavior appeared to depend on the speed of the vessel. The tuna remained within a few meters of the surface when the vessel was traveling at high speeds but moved deeper when the vessel drifted. The behavior of these fish is compared to those of other yellowfin tuna tracked in other situations (associated with fish-aggregating devices or unassociated with devices). The reasons for these associations are not known but some hypotheses are advanced.