Pacific lamprey (Entosphenus tridentatus) ammocoetes exposed to contaminated Portland Harbor sediments: Method development and effects on survival, growth, and behavior

Julia R Unrein, Jeffrey M Morris, Rob S Chitwood, Joshua Lipton, Jennifer Peers, Stan van de Wetering, Carl B Schreck

Many anthropogenic disturbances have contributed to the decline of Pacific lamprey (Entosphenus tridentatus), but potential negative effects of contaminants on lamprey are unclear. Lamprey ammocoetes are the only detritivorous fish in the Lower Willamette River, Oregon and have been observed in Portland Harbor sediments. Their long benthic larval stage places them at risk from the effects of contaminated sediment. We developed experimental methods to assess the effects of contaminated sediment on the growth and behavior of field-collected ammocoetes reared in a laboratory. Specifically, we developed methods to assess individual growth and burrowing behavior. Burrowing performance demonstrated high variability among contaminated sediments; however, ammocoetes presented with non-contaminated reference sediment initiated burrowing more rapidly and completed it faster. Ammocoete re-emergence from contaminated sediments suggests avoidance of some chemical compounds. We conducted long-term exposure experiments on individually held ammocoetes using sediment collected from their native Siletz River; contaminated sediments collected from 9 sites within Portland Harbor; 2 uncontaminated reference sediments collected upstream; 1 uncontaminated sediment with characteristics similar to Portland Harbor sediments; and clean sand. We determined a 24-h depuration period was sufficient to evaluate weight changes. We observed no mortality or growth effects in fish exposed to any of the contaminated sediments. However, the effect on burrowing behavior appeared to be a sensitive endpoint, with potentially significant implications for predator avoidance. This article is protected by copyright. All rights reserved.