FISHERY BULLETIN: VOL. 81, NO. 2 



surf smelt, Hypomesus pretiosus; shiner perch, 

 Cymatogaster aggregate; Pacific herring, Clupea 

 harengus pallasi; and English sole, Parophrys 

 uetulus, in Tillamook Bay (Forsberg et al. 12 ). All five 

 species were identified as prey of harbor seals using 

 Netarts Bay (see results of fecal analysis) and have 

 been commonly reported as food of harbor seals in 

 other areas (Pitcher 1980a; Bowlby 1981; Graybill 

 1981; Calambokidis et al. footnote 5; Beach et al. 

 footnote 9). 



The differences in seasonal abundances of harbor 

 seals at Netarts and Tillamook Bays may be in part 

 related to the quality of habitat available for pupping 

 and nursing. As in other areas (Johnson and Jeffries 

 footnote 7), harbor seals at Netarts and Tillamook 

 Bays use more haul-out sites within each bay during 

 the pupping season than at other times of the year. 

 Females with pups tend to form smaller, more 

 isolated groups, usually in the more remote parts of 

 the estuaries. Tillamook Bay, because of its greater 

 size and more varied bottom topography, has a larger 

 number of small channels in the upper portions of the 

 bay. These channels rarely carry boat traffic and so 

 offer access to a substantially greater number of pre- 

 ferred haul-out areas for female-pup pairs. 



Movements of Tagged Harbor Seals 



Between August 1978 and March 1979, 5 of 11 

 radio-tagged harbor seals (45.4%) made at least one 

 move from Netarts Bay to Tillamook Bay (a distance 

 by sea of about 25 km). Three of the five harbor seals 

 made at least one trip from Netarts Bay to Tillamook 

 Bay and back, and one visited both bays at least twice 

 (Fig. 4). The propensity for movement seemed to 

 vary among individuals. One harbor seal (no. 900) 

 moved between Netarts and Tillamook Bays at least 

 three times during the first 19 d following its release. 

 Another animal (no. 580) was resighted more often 

 and more regularly (27 times in 9 mo) than any other 

 seal, yet was always found at Netarts Bay. Harbor 

 seals carrying plastic tags have been identified at 

 Netarts Bay up to 29 mo after tagging. 



Long-range movements of harbor seals tagged in 

 1979, 1980, and 1981 include one harbor seal that 

 traveled 75 km south (Whale Cove; Fig. 1) and later 

 returned to Netarts Bay, and another animal that was 

 found hauled out among a large group of harbor seals 



about 220 km south of the tagging site (Winchester 

 Bay; Fig. 1). Single flipper tags from two harbor seals 

 were recovered during commercial fishing opera- 

 tions at two locations. One tag was found entangled in 

 a set herring gill net in Humboldt Bay, Calif., 550 km 

 south of Netarts Bay, and another tag was recovered 

 in a scallop drag fishing operation 75 km north of the 

 tagging site. 



Similar evidence of haul-out site fidelity and long- 

 distance movements in harbor seals has been report- 

 ed for other areas. A newborn pup, flipper-tagged on 

 Tugidak Island, Alaska, was found 3 yr later <5 km 

 from the tagging site (Divinyi 1971). Bonner and 

 Witthames (1974) reported the dispersal of 55 

 flipper- tagged juveniles from the Wash, East Anglia, 

 England, and their subsequent recovery up to 250 

 km from the tagging area. Pitcher and McAllister 

 (1981) radio-tagged 35 harbor seals in Alaska and 

 reported that while 8 animals had used haul-out 

 areas, ranging from 24 to 194 km from the tagging 

 site, 23 were found only at the hauling area where 

 they were captured. 



Predation on Chum Salmon at 

 Whiskey Creek 



Predation on chum salmon by harbor seals was not 

 often seen in other parts of the bay. Harbor seals 

 clearly took advantage of the concentrations of fish 

 that occurred as chum salmon funneled from the 

 wide open bay into the narrow mouth of Whiskey 

 Creek. Harbor seals preying on chum salmon in this 

 area took an estimated 6.1, 7.2, and 1.5% of the 1978, 

 1979, and 1980 returns, respectively (Table 2). It is 

 important to note that while the average number of 

 harbor seals feeding in this area per high tide was 

 similar from year to year, the percent loss of each 



Table 2.— Estimated impacts on 1978, 1979, and 1980 chum 

 salmon returns at Netarts Bay, Oreg. through predation by harbor 

 seals in the Whiskey Creek area. 



,: Forsberg, B. D., J. A. Johnson, and S. M. Klug. 1977. Identi- 

 fication, distribution, and notes of food habits offish and shellfish in 

 Tillamook Bay, Oregon. Federal Aid Progress Reports, Fisheries, 

 Contract No. 14-16-0001-5456RBS, Research Section, Oregon De- 

 partment of Fish and Wildlife, 117 p. 



296 



Observation periods averaged 4.1 and ranged from 1 .2 to 7.3 h in duration 



