Identification of the nutritional resources of larval sea lamprey in two Great Lakes tributaries using stable isotopes

Communicated by Michael Sierszen The sea lamprey (Petromyzon marinus) is an important invasive parasitic species in the Laurentian Great Lakes, but the nutritional subsidies supporting the protracted filter feeding ammocoete stage are not well established. We used stable isotope ratios (δC and δN) to determine themajor sources of autochthonous (aquatically produced) and allochthonous (terrestrially produced) organicmatter (OM) to the nutrition of ammocoetes collected in 2010 from the Pigeon and Jordan Rivers in Michigan (USA). Ammocoete δC was positively correlated with animal length and C:N ratio, but δN was not correlated with either, suggesting that ammocoetes are primary consumers. We used a Bayesian model (MixSIR) to estimate the contributions of potential nutritional sources to ammocoetes. Estimates suggest that aquatic sedimentsweremost important to ammocoete nutrition (median contributions ranged from 49–51%). Aquatic plants, including macrophytes and algae, were also important to ammocoete nutrition with a median contribution of 29%. Terrestrial plants were generally of lesser but still significant importance to ammocoetes, with a median contribution of 19–39%. Our findings generally agree with those of previous studies that have found that inputs of detrital and recently livingOM from aquatic primary producers both provide an important source of nutrition for ammocoetes. The present study provides more quantitative estimates of the different forms of OM supporting ammocoete nutrition and biomass. © 2015 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. Index words: Sea lamprey Stable isotopes Laurentian Great Lakes MixSIR Autochthonous Allochthonous