Evidence of marine mammal predation of the European eel (Anguilla anguilla L.) on its marine migration |
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| Institution: | 1. DTU Aqua-National Institute of Aquatic Resources, Section for Marine Ecology, Technical University of Denmark, Charlottenlund Slot, Jægersborg Allé 1, 2920 Charlottenlund, Denmark;2. Department of Biology, University of Windsor, 401 Sunset Ave, Windsor, Ontario N9B 3P4, Canada;3. Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Ave, Windsor, Ontario N9B 3P4, Canada |
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| Abstract: | Temperature and depth logging tags were implanted into adult eels released on Atlantic west coasts of France and Ireland to study their oceanic migration behavior. For three of the tags, 25 to 256 days after release there was a dramatic rise in temperature from 10 °C to 36 °C and the dive profile changed from depths of 300–1000 m to repeated ascents to the surface. This indicated that the eels carrying the tags had been eaten by a mammalian predator. Two of the tags had sufficient sampling rate to resolve the dives in detail. They recorded a total of 91 dives to maximum depths of 250–860 m lasting 11–12 min and with surface intervals of 5–7 min. More than two thirds of the dives included a rapid descent from approximately 500 m to 600–700 m. From this we infer that the predator was most likely a deep-diving toothed whale. The dives logged while the tags were inside the predator revealed that the temperature usually decreased during dives, and increased again during surface periods. The temperature drops during dives were probably caused by the ingestion of prey or water. These observations provide insights into the behavior of toothed whales foraging in the mesopelagic zone. |
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| Keywords: | Archival tag Eel Predation Diving behavior Toothed whale predator |
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