Geographic distribution and aspects of the parasite/host relationships of the invasive swim bladder parasite Anguillicoloides crassus infecting American eel (Anguilla rostrata) in mainland Nova Scotia and New Brunswick

Abstract

Between 2008-2013, 1,981 eels were collected from 174 localities throughout mainland Nova Scotia and New Brunswick and necropsied for the swim bladder nematode Anguillicoloides crassus. Overall prevalence of A. crassus was 4% with a mean intensity of 3.8± 8 SD (1-63 parasites). The Southern Uplands, Gulf of St. Lawrence and the Bay of Fundy regions were all identified as having rivers with eels infected with the nematode. The prevalence within the Bay of Fundy region was 7.4% (40/539) with infected eels found in the Saint John River and Shubenacadie River. The Southern Uplands had a prevalence of 2.4% (34/1395) with a focus of infection in the Mersey and Medway Rivers. Finally, the Gulf region had a prevalence of 4% (2/47), with a single site West River, Antigonish having the 2 infected fish. Condition factor, HSI, and SSI did not correlate with eel length and weight. Infected fish were significantly longer and heavier than non infected eels sampled. Information obtained on the distribution of the parasite in the present study is joined with previously published surveys, revealing the parasite to be in the St. John River and throughout Cape Breton with isolated localities in Mersey, Medway, St, Mary`s and Salmon (Halifax Co.) River. Further work is needed to monitor the spread of A. crassus and to understand how eels are adapting or not, to this invasive parasite in Atlantic Canada.