Research Document - 2012/082

Occurrences of Anguillicoloides crassus, an invasive parasitic nematode, infecting American eel (Anguilla rostrata) collected from New Brunswick and Nova Scotia Rivers: 2008-2009

By D.M. Campbell, R.G. Bradford, and K.M.M. Jones

Abstract

The exotic swim bladder nematode (Anguillicoloides crassus) is widespread among American eel (Anguilla rostrata) inhabiting the coastal and inland waters of the eastern United States, and has recently been detected in New Brunswick (NB) and Nova Scotia (NS) waters. There is concern that this parasite, which can damage the swim bladder of the American eel hosts, could potentially reduce the ability of infected adult eels to migrate and spawn successfully in the Sargasso Sea. To better understand the distribution of A. crassus within the waterways of NB and NS, 1,965 eels were collected for necropsy during the years 2008 and 2009, from 177 sites distributed among 61 river drainages. In total, A. crassus were found in the swim bladders of 49 eels collected from 22 of the sites and 8 drainages. Prevalence (P) of infection was higher among NB samples (38 of 479 eels; P = 7.9%) than NS samples (11 of 1,486 eels; P = 0.7%). Mean intensity (number of A. crassus per infected eel) was generally low, 2.3 for all samples combined and 2.6 and 1.5 for NB and NS samples, respectively. The number of A. crassus per eel was 3 or less in 90% of the cases where it was detected. All detected occurrences of A. crassus identified in NB were within the Saint John River, where prevalence was estimated at 10.1%, and at least 1 eel at 15 sites was infected. Information from all available sources indicates that both prevalence and intensity of A. crassus may be higher in tidal waters than in freshwater, but additional work will be required to affirm that this is the case.

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