Seasonal abundance, size, and host selection of western river (Lampetra ayresii) and Pacific (Entosphenus tridentatus) lampreys in the Columbia River estuary

Little is known about the basic biology and ecology of most native lampreys, including the use of estuaries by anadromous lampreys. To address this deficiency, we provide the first analysis of anadromous western river (Lampetra ayresii) and Pacific (Entosphenus tridentatus) lampreys in the Columbia River estuary, using data from 2 fish assemblage studies that span 3 decades (1980-1981 and 2001-2012). Pacific lamprey juveniles and adults in the estuary clearly were separated by size, whereas western river lamprey formed one continuous size distribution. Pacific lamprey juveniles and adults were present in the estuary in winter and spring, and western river lamprey were present from spring through early fall. Depth in the water column also differed by lamprey species and age class. During 2008-2012, we documented wounds from lampreys on 8 fish species caught in the estuary. The most frequently wounded fishes were non-native American shad (Alosa sapidissima), subyearling Chinook salmon (Oncorhynchus tshawytscha), shiner perch (Cymatogaster aggregata), and Pacific herring (Clupea pallasii). This basic information on western river and Pacific lampreys in the Columbia River estuary adds to the growing body of regional research that should aid conservation efforts for these ancient species.