Prevalences of Microphallus sp. and the unidentified trematodemetacercaria showed overall negative relationships with increas-ing water abstraction, thereby supporting our second hypothesis(Fig. 3). However, the relationship for the trematode metacer-caria with water abstraction needs to be interpreted with cautionbecause this taxon was only detected from 5 sites and the best-fitting model explained only 22% of the variation in the data. Highwater abstraction reduces the area of suitable in-stream habitat forthe snail intermediate hosts, and this is likely to constrain theirtransmission rates. Flow reduction often results in a decrease incurrent velocity and available favourable habitats (Dewson et al.,2007). These changes may negatively affect development and sur-vival of infective free-living parasite stages (egg and/or larvalstages) and snail host density. Lange et al. (2014a) found that waterabstraction in the Manuherikia River had a negative effect on therelative abundance of Potamopyrgus, possibly due to the reductionof the riverine habitat and increased probability of stream drying.Overall, high levels of water abstractions may have negative effectson abundance of snail hosts and on transmission rates betweendifferent hosts, especially where streams are falling dry, whichcauses a dramatic disturbance to stream ecosystem functioning(Lake, 2003).