Swimming performance of silver eels is severely impaired by the swim-bladder parasite Anguillicola crassus

A. P. Palstra, D. F.M. Heppener, V. J.T. van Ginneken, C. Székely, G. E.E.J.M. van den Thillart

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Abstract

Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activities - related to parasite weight - reduce swimming endurance, while mechanical damage of the swim-bladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (< 0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (< 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.

Original languageEnglish
Pages (from-to)244-256
Number of pages13
JournalJournal of Experimental Marine Biology and Ecology
Volume352
Issue number1
DOIs
Publication statusPublished - Nov 30 2007

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Keywords

  • Anguillicola crassus (Kuwahara, Niimi and Hagaki, 1974)
  • Environmental constraint
  • European eel Anguilla anguilla (Linnaeus 1758)
  • Oxygen consumption
  • Reproductive migration
  • Swimming efficiency
  • Swimming endurance

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science

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