NOTES ON THE MARINE LIFE OF 



THE RIVER LAMPREY, LAMPETRA AYRESI, 



IN YAQUINA BAY, OREGON, AND 



THE COLUMBIA RIVER ESTUARY 1 



The river lamprey, Lampetra ayresi, although 

 uncommon in Oregon, is collected occasionally in 

 the surface waters of the ocean and in estuaries. 

 The species appears to be most abundant in the 

 Columbia River estuary and is often found in 

 Yaquina Bay. Systematic sampling programs in 

 those two estuaries, carried out by the National 

 Marine Fisheries Service (NMFS) in the 

 Columbia River estuary and by Oregon State 

 University in Yaquina Bay, have provided suffi- 

 cient specimens (225) so that a preliminary 

 assessment of the saltwater life of the species in 

 Oregon can be attempted and comparisons made 

 with its life history in British Columbia as 

 reported by Beamish (1980). 



The capture of river lampreys and the sam- 

 pling program by which specimens were ob- 

 tained are described or outlined by Dawley et 

 al.. 2 Durkin et al., 3 and Myers (1980). River 

 lampreys were usually caught incidentally in 

 studies of other species and were taken by means 

 of beach seine, purse seine, lampara net, and 



'Technical Paper No. 6201, Oregon Agricultural Experi- 

 ment Station, Oregon State University, Corvallis, OR 97331. 



2 Dawley, E. M., C. Sims, R. D. Ledgerwood, D. R. Miller, and 

 J.G.Williams. 1981. Study to define the migrational char- 

 acteristics of chinook and coho salmon in the Columbia River 

 estuary and associated marine waters. Progress report of 

 coastal zone and estuarine studies. Pacific Northwest Regional 

 Commission and Coastal Zone and Estuarine Studies Division. 

 Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service. NOAA, Seattle. WA 98195. 



3 Durkin, J. T., T. C. Coley, J. T. McCabe, Jr., W. D. Muir. K. 

 Verner. and R. L. Emmett. 1981. Non-salmonid, salmonid 

 fishes. In Columbia River Estuary Data Development Pro- 

 gram, 1979-80 Annual Report, Vol. 2, p. 1-24, Pacific North- 

 west River Basins Commission. National Marine Fisheries 

 Service, NOAA. Hammond. OR 97121. 



bottom trawl. Mesh sizes of the nets employed 

 were usually 6.5 mm or 9.5 mm bar measure, 

 thus selection for larger individuals was prob- 

 able. Additional specimens were obtained from a 

 variety of sources. Specimens are held in the fish 

 collection of the Department of Fisheries and 

 Wildlife, Oregon State University (OS). 



Downstream Migration 



In British Columbia, river lampreys entering 

 saltwater from late April to early July averaged 

 110 mm total length (TL); the range of lengths 

 was 40-190 mm (Beamish 1980). We have no 

 downstream migrants from freshwater, but we 

 have two lots (OS 7320-1) that include specimens 

 115 mm long taken in marine waters on 21 May 

 1980. The earliest collection of the year of marine 

 specimens in Oregon was made 5 May. One 

 specimen measuring 161 mm long (OS 7370) 

 from the Pacific Ocean and another measuring 

 206 mm (OS 4630) from Yaquina Bay were 

 collected on that day. Both were immature and 

 had been feeding. Because early May corre- 

 sponds to the spawning season, the two feeders 

 must have migrated early and apparently would 

 have matured after the summer feeding season. 



From mid-May to mid-June, specimens taken 

 from Yaquina Bay with a 9.5 mm-mesh seine 

 ranged in length from 141 to 245 mm (Table 1). 

 In the same period, specimens taken by various 

 nets (including some of 6.5 mm mesh) from the 

 Columbia River estuary ranged from 115 to 278 

 mm. Specimens captured in the Pacific Ocean 

 between mid-May and 25 June ranged from 145 

 to 237 mm. The distribution over the size range is 

 sparse so that modes are difficult to recognize, 

 except that in the Columbia estuary series (OS 

 6852, 6856, 6857) for 4 June (n = 110) 62% of the 

 specimens fall between 160 and 210 mm. 



Table 1.— Ranges and means of total length of river lampreys captured in 

 saltwater off Oregon (by half-month periods, all years combined). 



FISHERY BULLETIN: VOL. 81. NO. 1. 1983. 



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