Parasitism of Rainbow Trout in Hatchery Raceways by Chestnut Lampreys

Abstract

AbstractOther than anecdotal evidence, parasitism of trout by lampreys in hatcheries has not been characterized. This study investigated the frequency of parasitism on Rainbow Trout Oncorhynchus mykiss by presumptive Chestnut Lampreys Ichthyomyzon castaneus in the raceways of Norfork National Fish Hatchery (northern Arkansas) from January to April 2013. Although no Chestnut Lampreys were collected, 82 wounded trout were identified from 23 of the 54 raceways sampled, with frequencies of parasitism being greatest during April. We also examined attachment site selection; 95% of attachments were dorsal, and most were in the mid‐section of the host fish. Data indicating preference for a dorsal attachment site selection are consistent with observations generated in most studies of Chestnut Lampreys. Although not significant in terms of trout lost to parasitism, efforts should be maintained to minimize lamprey invasion into hatcheries, as the zoonotic transfer of pathogens has been documented in other lampreys.