Journal
HYDROBIOLOGIA
Volume 483, Issue 1-3, Pages 103-110Publisher
SPRINGER
DOI: 10.1023/A:1021359008246
Keywords
tigerfish; activity rhythms; predation; Africa; telemetry
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The ecology and behaviour of tigerfishes (Hydrocynus spp., Alestiidae) remains largely unknown despite these piscivores play a crucial role in tropical ecosystems. A 44-cm tigerfish H. brevis was equipped with two transmitters using accelerometer and depth sensors, the signals of which were simultaneously recorded while tracking the fish over four 24-h cycles during February and March 2001 in the River Niger near Bamako, Mali. This methodology permitted discriminating between different behaviours, including hunting sequences. Over 1 month, the tigerfish occupied an area of no more than 3 ha over one third of the river width, and showed consistent fidelity to the same activity core ( circa 0.1 ha), which consisted in a calm (< 10 cm s(-1)) glide with depth ranging from 60 to 100 cm, and comprising many large immersed rocks. Activity was essentially diurnal, with no hunting sequence observed at light intensities < 0.01 Lux. It decreased under gusting winds or when boat traffic was intense and forced the fish to deeper ( c. 1.5 m) waters. These preliminary results support the idea that H. brevis is essentially a diurnal, visually orientated predator with strong sedentary habits during the mid-dry season, and that its predatory activity might be compromised by the intensification of boat traffic.
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