Orr et al.: Foraging habits of Phoca vitulma richardsi in the Umpqua River, Oregon 



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Pacific Ocean 



A 



N 



the surface (Bigg et al., 1990); however, 

 consumption is typically determined by 

 examining scat (fecal) samples. In the 

 past, species-specific sagittal otoliths 

 found in scats were used exclusively 

 to determine the identification of prey 

 taxa. However, because otoliths can be 

 partially or completely digested, or are 

 not present in scats (because the head of 

 the prey was not consumed ), they are not 

 always an adequate representation of di- 

 et. Recently, investigators have begun to 

 use additional structures (e.g. cranial el- 

 ements, vertebrae) recovered from scats 

 to identify prey (e.g. Olesiuk et al., 1990; 

 Cottrell et al., 1996; Riemer and Brown, 

 1997; Browne et al., 2002; Lance et al. 2 ). 

 These structures usually are more com- 

 mon than otoliths and frequently can be 

 identified to species; however, bones of 

 some species can be identified to family 

 only (e.g. salmonids). Consequently, the 

 National Marine Mammal Laboratory 

 (NMML) collaborated with the Conser- 

 vation Biology Molecular Genetics 

 Laboratory (CBMGL; Northwest Fish- 

 eries Science Center, Seattle, WA) to 

 develop molecular genetic identification 

 of salmonid species (Purcell et al., 2004). 

 Because of the complex salmonid species 

 composition in the Umpqua River, genetic identification 

 was vital to distinguish species that were rare from those 

 that were abundant. 



The original impetus of this study was to assess the 

 impact of harbor seal predation on the recovery of the 

 Umpqua River sea-run cutthroat trout (O. clarkii) that 

 were listed as endangered under the Endangered Species 

 Act (ESA) during 1996 (Johnson et al., 1999). Umpqua 

 River cutthroat trout were removed from the ESA in 2000 

 because they were identified to be part of the larger Oregon 

 Coast evolutionary significant unit (U.S. Fish and Wildlife 

 Service, 2000). The present study was continued despite 

 the "delisting" of cutthroat trout because the Umpqua is 

 inhabited year-round by harbor seals that haul out sev- 

 eral kilometers upriver and is, thus, ideal for determining 

 whether the presence of a pinniped species within a sys- 

 tem is indicative of substantial feeding on fish species of 

 concern within that environment. In addition, the Umpqua 

 River contains several other salmonid species whose status 

 is precarious (NMFS, 1997). Therefore, the development of 

 genetic identification techniques was considered valuable 

 for this system, as well as for future foraging studies in 

 which species-specific identification may be desirable but 

 impossible by way of conventional identification methods. 



Oregon 



L mpquu River 



hauiouts 



2 Lance, M., A. Orr, S. Riemer, M. Weise, and J. Laake. 2001. 

 Pinniped food habits and prev identification techniques pro- 

 tocol. AFSC Proc. Rep. 2001-04, 36 p. AFSC, NMFS, NOAA. 

 7600 Sand Point Way NE, Seattle. WA 98115. 



Figure 1 



Map of the lower section of the Umpqua River, Oregon, where scat samples were 

 collected at two haulout sites during 1997 and 1998. 



The objectives of this study were 1 ) to determine by an 

 examination of diet if harbor seals that haul out in the 

 Umpqua River feed primarily in the river or elsewhere, 

 and 2) to apply genetic techniques to identify salmonid 

 prey species. 



Materials and methods 



Study area 



The Umpqua River, located in southern Oregon ( Fig. 1 ). is 

 a natal river for sea-run cutthroat trout, as well as chinook 

 (O. tshawytscha), coho (O. kisutch) salmon, and steelhead 

 trout (O. mykiss). The Umpqua estuary is also inhabited 

 year-round by approximately 600-1000 harbor seals and 

 has been designated as an area where pinnipeds and sal- 

 monids significantly co-occur (NMFS, 1997). Scat samples 

 for this study were collected from two hauiouts located 

 within 4.8 km of the river's mouth and within 1.6 km of 

 each other (Fig. 1). 



Scat collection and analysis 



Samples were collected during two seasons: "spring" 

 (March through June) and "fall" (August to December). 

 "Spring" corresponded to the migration of anadromous 

 cutthroat trout adults and some juveniles to the ocean and 

 "fall" coincided approximately with the freshwater return 

 of spawning anadromous adults. The migratory and spawn- 



