Ichthyophthirius multifiliis in Elvers and Small American Eels from the East River,Nova Scotia

Abstract

Elvers of American eels Anguilla rostrata entering the East River on the Atlantic coast of Nova Scotia between early May and the end of July were parasitized by Ichthyophthirius multifiliis during June of 1993 for the first time in 6 years of observation. Prevalence of infection in elvers (49.9–68.2 mm total length, TL) ranged from 7 to 30%; weekly mean prevalence (pooled sample) ranged from 13.0 to 23.3% over an infection period of 42 d. Weekly prevalence ranged from 8.3 to 12.2% for small eels (70–120 mm TL). Mean intensity of infection was 6.1 trophonts/host (range, 1–61) for elvers and 7.2 trophonts/host (range, 1–40) for small eels. Count distributions were right-skewed and leptokurtic for both elvers and small eels. No conclusion could be made (due to low statistical power) as to whether length or weight was related to mean intensity of parasitism in either elvers or small eels or whether mean intensity differed between elvers and small eels. High river discharge during June–July, but not water temperature (April–July), may have contributed to development of the epizootic of I. multifiliis in 1993.